Programs & Examples On #Aggregates

Aggregate functions, typically found in SQL, derive summary values from multiple rows in a single column.

SQL Server Pivot Table with multiple column aggregates

I used your own pivot as a nested query and came to this result:

SELECT
  [sub].[chardate],
  SUM(ISNULL([Australia], 0)) AS [Transactions Australia],
  SUM(CASE WHEN [Australia] IS NOT NULL THEN [TotalAmount] ELSE 0 END) AS [Amount Australia],
  SUM(ISNULL([Austria], 0)) AS [Transactions Austria],
  SUM(CASE WHEN [Austria] IS NOT NULL THEN [TotalAmount] ELSE 0 END) AS [Amount Austria]
FROM
(
  select * 
  from  mytransactions
  pivot (sum (totalcount) for country in ([Australia], [Austria])) as pvt
) AS [sub]
GROUP BY
  [sub].[chardate],
  [sub].[numericmonth]
ORDER BY 
  [sub].[numericmonth] ASC

Here is the Fiddle.

Aggregate / summarize multiple variables per group (e.g. sum, mean)

With the dplyr package, you can use summarise_all, summarise_at or summarise_if functions to aggregate multiple variables simultaneously. For the example dataset you can do this as follows:

library(dplyr)
# summarising all non-grouping variables
df2 <- df1 %>% group_by(year, month) %>% summarise_all(sum)

# summarising a specific set of non-grouping variables
df2 <- df1 %>% group_by(year, month) %>% summarise_at(vars(x1, x2), sum)
df2 <- df1 %>% group_by(year, month) %>% summarise_at(vars(-date), sum)

# summarising a specific set of non-grouping variables using select_helpers
# see ?select_helpers for more options
df2 <- df1 %>% group_by(year, month) %>% summarise_at(vars(starts_with('x')), sum)
df2 <- df1 %>% group_by(year, month) %>% summarise_at(vars(matches('.*[0-9]')), sum)

# summarising a specific set of non-grouping variables based on condition (class)
df2 <- df1 %>% group_by(year, month) %>% summarise_if(is.numeric, sum)

The result of the latter two options:

    year month        x1         x2
   <dbl> <dbl>     <dbl>      <dbl>
1   2000     1 -73.58134  -92.78595
2   2000     2 -57.81334 -152.36983
3   2000     3 122.68758  153.55243
4   2000     4 450.24980  285.56374
5   2000     5 678.37867  384.42888
6   2000     6 792.68696  530.28694
7   2000     7 908.58795  452.31222
8   2000     8 710.69928  719.35225
9   2000     9 725.06079  914.93687
10  2000    10 770.60304  863.39337
# ... with 14 more rows

Note: summarise_each is deprecated in favor of summarise_all, summarise_at and summarise_if.


As mentioned in my comment above, you can also use the recast function from the reshape2-package:

library(reshape2)
recast(df1, year + month ~ variable, sum, id.var = c("date", "year", "month"))

which will give you the same result.

What are Aggregates and PODs and how/why are they special?

What changes in

Following the rest of the clear theme of this question, the meaning and use of aggregates continues to change with every standard. There are several key changes on the horizon.

Types with user-declared constructors P1008

In C++17, this type is still an aggregate:

struct X {
    X() = delete;
};

And hence, X{} still compiles because that is aggregate initialization - not a constructor invocation. See also: When is a private constructor not a private constructor?

In C++20, the restriction will change from requiring:

no user-provided, explicit, or inherited constructors

to

no user-declared or inherited constructors

This has been adopted into the C++20 working draft. Neither the X here nor the C in the linked question will be aggregates in C++20.

This also makes for a yo-yo effect with the following example:

class A { protected: A() { }; };
struct B : A { B() = default; };
auto x = B{};

In C++11/14, B was not an aggregate due to the base class, so B{} performs value-initialization which calls B::B() which calls A::A(), at a point where it is accessible. This was well-formed.

In C++17, B became an aggregate because base classes were allowed, which made B{} aggregate-initialization. This requires copy-list-initializing an A from {}, but from outside the context of B, where it is not accessible. In C++17, this is ill-formed (auto x = B(); would be fine though).

In C++20 now, because of the above rule change, B once again ceases to be an aggregate (not because of the base class, but because of the user-declared default constructor - even though it's defaulted). So we're back to going through B's constructor, and this snippet becomes well-formed.

Initializing aggregates from a parenthesized list of values P960

A common issue that comes up is wanting to use emplace()-style constructors with aggregates:

struct X { int a, b; };
std::vector<X> xs;
xs.emplace_back(1, 2); // error

This does not work, because emplace will try to effectively perform the initialization X(1, 2), which is not valid. The typical solution is to add a constructor to X, but with this proposal (currently working its way through Core), aggregates will effectively have synthesized constructors which do the right thing - and behave like regular constructors. The above code will compile as-is in C++20.

Class Template Argument Deduction (CTAD) for Aggregates P1021 (specifically P1816)

In C++17, this does not compile:

template <typename T>
struct Point {
    T x, y;
};

Point p{1, 2}; // error

Users would have to write their own deduction guide for all aggregate templates:

template <typename T> Point(T, T) -> Point<T>;

But as this is in some sense "the obvious thing" to do, and is basically just boilerplate, the language will do this for you. This example will compile in C++20 (without the need for the user-provided deduction guide).

Initializing a member array in constructor initializer

You want to init an array of ints in your constructor? Point it to a static array.

class C 
{
public:
    int *cArray;

};

C::C {
    static int c_init[]{1,2,3};
    cArray = c_init;
}

Is there any difference between GROUP BY and DISTINCT

I know it's an old post. But it happens that I had a query that used group by just to return distinct values when using that query in toad and oracle reports everything worked fine, I mean a good response time. When we migrated from Oracle 9i to 11g the response time in Toad was excellent but in the reporte it took about 35 minutes to finish the report when using previous version it took about 5 minutes.

The solution was to change the group by and use DISTINCT and now the report runs in about 30 secs.

I hope this is useful for someone with the same situation.

What does it mean "No Launcher activity found!"

Do you have an activity set up the be the launched activity when the application starts?

This is done in your Manifest.xml file, something like:

    <activity android:name=".Main" android:label="@string/app_name"
        android:screenOrientation="portrait">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

PowerShell: Store Entire Text File Contents in Variable

To get the entire contents of a file:

$content = [IO.File]::ReadAllText(".\test.txt")

Number of lines:

([IO.File]::ReadAllLines(".\test.txt")).length

or

(gc .\test.ps1).length

Sort of hackish to include trailing empty line:

[io.file]::ReadAllText(".\desktop\git-python\test.ps1").split("`n").count

HTTP Error 403.14 - Forbidden - The Web server is configured to not list the contents of this directory

I solved my problem with fallow this steps =>

  1. Open IIS Manager
  2. Click the Application
  3. Click Directory Browsing
  4. Click Open Feature (On the right you will see under Actions)
  5. Click Enable

Get today date in google appScript

Google Apps Script is JavaScript, the date object is initiated with new Date() and all JavaScript methods apply, see doc here

How do I space out the child elements of a StackPanel?

sometimes you need to set Padding, not Margin to make space between items smaller than default

XAMPP MySQL password setting (Can not enter in PHPMYADMIN)

1.open your xampp dir ( c:/xampp )

2.to phpMyadmin dir [C:\xampp\phpMyAdmin]

3.open [ config.inc.php ] file with any text editor

$cfg['Servers'][$i]['auth_type'] = 'config'; //replace 'config' to ‘cookie’
$cfg['Servers'][$i]['AllowNoPassword'] = true; //change ‘true’ to ‘false’.

last : save the file .

here is a video link in case you want to see it in Action [ click Here ]

Show/hide image with JavaScript

It's pretty simple.

HTML:

<img id="theImage" src="yourImage.png">
<a id="showImage">Show image</a>

JavaScript:

document.getElementById("showImage").onclick = function() {
    document.getElementById("theImage").style.visibility = "visible";
}

CSS:

#theImage { visibility: hidden; }

Eclipse shows errors but I can't find them

Take a look at

Window ? Show View ? Problems

or

Window ? Show View ? Error Log

Reload content in modal (twitter bootstrap)

You can force Modal to refresh the popup by adding this line at the end of the hide method of the Modal plugin (If you are using bootstrap-transition.js v2.1.1, it should be at line 836)

this.$element.removeData()

Or with an event listener

$('#modal').on('hidden', function() {
    $(this).data('modal').$element.removeData();
})

Any shortcut to initialize all array elements to zero?

In java all elements(primitive integer types byte short, int, long) are initialised to 0 by default. You can save the loop.

How to get the id of the element clicked using jQuery

update as you loading contents dynamically so you use.

$(document).on('click', 'span', function () {
    alert(this.id);
});

old code

$('span').click(function(){
    alert(this.id);
});

or you can use .on

$('span').on('click', function () {
    alert(this.id);
});

this refers to current span element clicked

this.id will give the id of the current span clicked

error, string or binary data would be truncated when trying to insert

I had the same issue. The length of my column was too short.

What you can do is either increase the length or shorten the text you want to put in the database.

How to change the server port from 3000?

In package.json set the following command (example for running on port 82)

"start": "set PORT=82 && ng serve --ec=true"

then npm start

How can I get a resource "Folder" from inside my jar File?

I know this is many years ago . But just for other people come across this topic. What you could do is to use getResourceAsStream() method with the directory path, and the input Stream will have all the files name from that dir. After that you can concat the dir path with each file name and call getResourceAsStream for each file in a loop.

How to dispatch a Redux action with a timeout?

It is simple. Use trim-redux package and write like this in componentDidMount or other place and kill it in componentWillUnmount.

componentDidMount() {
  this.tm = setTimeout(function() {
    setStore({ age: 20 });
  }, 3000);
}

componentWillUnmount() {
  clearTimeout(this.tm);
}

Break a previous commit into multiple commits

git rebase --interactive can be used to split a commit into smaller commits. The Git docs on rebase have a concise walkthrough of the process - Splitting Commits:

In interactive mode, you can mark commits with the action "edit". However, this does not necessarily mean that git rebase expects the result of this edit to be exactly one commit. Indeed, you can undo the commit, or you can add other commits. This can be used to split a commit into two:

  • Start an interactive rebase with git rebase -i <commit>^, where <commit> is the commit you want to split. In fact, any commit range will do, as long as it contains that commit.

  • Mark the commit you want to split with the action "edit".

  • When it comes to editing that commit, execute git reset HEAD^. The effect is that the HEAD is rewound by one, and the index follows suit. However, the working tree stays the same.

  • Now add the changes to the index that you want to have in the first commit. You can use git add (possibly interactively) or git gui (or both) to do that.

  • Commit the now-current index with whatever commit message is appropriate now.

  • Repeat the last two steps until your working tree is clean.

  • Continue the rebase with git rebase --continue.

If you are not absolutely sure that the intermediate revisions are consistent (they compile, pass the testsuite, etc.) you should use git stash to stash away the not-yet-committed changes after each commit, test, and amend the commit if fixes are necessary.

How to declare and initialize a static const array as a class member?

// in foo.h
class Foo {
    static const unsigned char* Msg;
};

// in foo.cpp
static const unsigned char Foo_Msg_data[] = {0x00,0x01};
const unsigned char* Foo::Msg = Foo_Msg_data;

Serializing class instance to JSON

The basic problem is that the JSON encoder json.dumps() only knows how to serialize a limited set of object types by default, all built-in types. List here: https://docs.python.org/3.3/library/json.html#encoders-and-decoders

One good solution would be to make your class inherit from JSONEncoder and then implement the JSONEncoder.default() function, and make that function emit the correct JSON for your class.

A simple solution would be to call json.dumps() on the .__dict__ member of that instance. That is a standard Python dict and if your class is simple it will be JSON serializable.

class Foo(object):
    def __init__(self):
        self.x = 1
        self.y = 2

foo = Foo()
s = json.dumps(foo) # raises TypeError with "is not JSON serializable"

s = json.dumps(foo.__dict__) # s set to: {"x":1, "y":2}

The above approach is discussed in this blog posting:

    Serializing arbitrary Python objects to JSON using __dict__

Developing C# on Linux

MonoDevelop, the IDE associated with Mono Project should be enough for C# development on Linux. Now I don't know any good profilers and other tools for C# development on Linux. But then again mind you, that C# is a language more native to windows. You are better developing C# apps for windows than for linux.

EDIT: When you download MonoDevelop from the Ubuntu Software Center, it will contain pretty much everything you need to get started right away (Compiler, Runtime Environment, IDE). If you would like more information, see the following links:

Python 2.7.10 error "from urllib.request import urlopen" no module named request

You can program defensively, and do your import as:

try:
    from urllib.request import urlopen
except ImportError:
    from urllib2 import urlopen

and then in the code, just use:

data = urlopen(MIRRORS).read(AMOUNT2READ)

What is the difference between persist() and merge() in JPA and Hibernate?

This is coming from JPA. In a very simple way:

  • persist(entity) should be used with totally new entities, to add them to DB (if entity already exists in DB there will be EntityExistsException throw).

  • merge(entity) should be used, to put entity back to persistence context if the entity was detached and was changed.

How to create json by JavaScript for loop?

var sels = //Here is your array of SELECTs
var json = { };

for(var i = 0, l = sels.length; i < l; i++) {
  json[sels[i].id] = sels[i].value;
}

Why can't a text column have a default value in MySQL?

Without any deep knowledge of the mySQL engine, I'd say this sounds like a memory saving strategy. I assume the reason is behind this paragraph from the docs:

Each BLOB or TEXT value is represented internally by a separately allocated object. This is in contrast to all other data types, for which storage is allocated once per column when the table is opened.

It seems like pre-filling these column types would lead to memory usage and performance penalties.

The definitive guide to form-based website authentication

PART I: How To Log In

We'll assume you already know how to build a login+password HTML form which POSTs the values to a script on the server side for authentication. The sections below will deal with patterns for sound practical auth, and how to avoid the most common security pitfalls.

To HTTPS or not to HTTPS?

Unless the connection is already secure (that is, tunneled through HTTPS using SSL/TLS), your login form values will be sent in cleartext, which allows anyone eavesdropping on the line between browser and web server will be able to read logins as they pass through. This type of wiretapping is done routinely by governments, but in general, we won't address 'owned' wires other than to say this: Just use HTTPS.

In essence, the only practical way to protect against wiretapping/packet sniffing during login is by using HTTPS or another certificate-based encryption scheme (for example, TLS) or a proven & tested challenge-response scheme (for example, the Diffie-Hellman-based SRP). Any other method can be easily circumvented by an eavesdropping attacker.

Of course, if you are willing to get a little bit impractical, you could also employ some form of two-factor authentication scheme (e.g. the Google Authenticator app, a physical 'cold war style' codebook, or an RSA key generator dongle). If applied correctly, this could work even with an unsecured connection, but it's hard to imagine that a dev would be willing to implement two-factor auth but not SSL.

(Do not) Roll-your-own JavaScript encryption/hashing

Given the perceived (though now avoidable) cost and technical difficulty of setting up an SSL certificate on your website, some developers are tempted to roll their own in-browser hashing or encryption schemes in order to avoid passing cleartext logins over an unsecured wire.

While this is a noble thought, it is essentially useless (and can be a security flaw) unless it is combined with one of the above - that is, either securing the line with strong encryption or using a tried-and-tested challenge-response mechanism (if you don't know what that is, just know that it is one of the most difficult to prove, most difficult to design, and most difficult to implement concepts in digital security).

While it is true that hashing the password can be effective against password disclosure, it is vulnerable to replay attacks, Man-In-The-Middle attacks / hijackings (if an attacker can inject a few bytes into your unsecured HTML page before it reaches your browser, they can simply comment out the hashing in the JavaScript), or brute-force attacks (since you are handing the attacker both username, salt and hashed password).

CAPTCHAS against humanity

CAPTCHA is meant to thwart one specific category of attack: automated dictionary/brute force trial-and-error with no human operator. There is no doubt that this is a real threat, however, there are ways of dealing with it seamlessly that don't require a CAPTCHA, specifically properly designed server-side login throttling schemes - we'll discuss those later.

Know that CAPTCHA implementations are not created alike; they often aren't human-solvable, most of them are actually ineffective against bots, all of them are ineffective against cheap third-world labor (according to OWASP, the current sweatshop rate is $12 per 500 tests), and some implementations may be technically illegal in some countries (see OWASP Authentication Cheat Sheet). If you must use a CAPTCHA, use Google's reCAPTCHA, since it is OCR-hard by definition (since it uses already OCR-misclassified book scans) and tries very hard to be user-friendly.

Personally, I tend to find CAPTCHAS annoying, and use them only as a last resort when a user has failed to log in a number of times and throttling delays are maxed out. This will happen rarely enough to be acceptable, and it strengthens the system as a whole.

Storing Passwords / Verifying logins

This may finally be common knowledge after all the highly-publicized hacks and user data leaks we've seen in recent years, but it has to be said: Do not store passwords in cleartext in your database. User databases are routinely hacked, leaked or gleaned through SQL injection, and if you are storing raw, plaintext passwords, that is instant game over for your login security.

So if you can't store the password, how do you check that the login+password combination POSTed from the login form is correct? The answer is hashing using a key derivation function. Whenever a new user is created or a password is changed, you take the password and run it through a KDF, such as Argon2, bcrypt, scrypt or PBKDF2, turning the cleartext password ("correcthorsebatterystaple") into a long, random-looking string, which is a lot safer to store in your database. To verify a login, you run the same hash function on the entered password, this time passing in the salt and compare the resulting hash string to the value stored in your database. Argon2, bcrypt and scrypt store the salt with the hash already. Check out this article on sec.stackexchange for more detailed information.

The reason a salt is used is that hashing in itself is not sufficient -- you'll want to add a so-called 'salt' to protect the hash against rainbow tables. A salt effectively prevents two passwords that exactly match from being stored as the same hash value, preventing the whole database being scanned in one run if an attacker is executing a password guessing attack.

A cryptographic hash should not be used for password storage because user-selected passwords are not strong enough (i.e. do not usually contain enough entropy) and a password guessing attack could be completed in a relatively short time by an attacker with access to the hashes. This is why KDFs are used - these effectively "stretch the key", which means that every password guess an attacker makes causes multiple repetitions of the hash algorithm, for example 10,000 times, which causes the attacker to guess the password 10,000 times slower.

Session data - "You are logged in as Spiderman69"

Once the server has verified the login and password against your user database and found a match, the system needs a way to remember that the browser has been authenticated. This fact should only ever be stored server side in the session data.

If you are unfamiliar with session data, here's how it works: A single randomly-generated string is stored in an expiring cookie and used to reference a collection of data - the session data - which is stored on the server. If you are using an MVC framework, this is undoubtedly handled already.

If at all possible, make sure the session cookie has the secure and HTTP Only flags set when sent to the browser. The HttpOnly flag provides some protection against the cookie being read through XSS attack. The secure flag ensures that the cookie is only sent back via HTTPS, and therefore protects against network sniffing attacks. The value of the cookie should not be predictable. Where a cookie referencing a non-existent session is presented, its value should be replaced immediately to prevent session fixation.

Session state can also be maintained on the client side. This is achieved by using techniques like JWT (JSON Web Token).

PART II: How To Remain Logged In - The Infamous "Remember Me" Checkbox

Persistent Login Cookies ("remember me" functionality) are a danger zone; on the one hand, they are entirely as safe as conventional logins when users understand how to handle them; and on the other hand, they are an enormous security risk in the hands of careless users, who may use them on public computers and forget to log out, and who may not know what browser cookies are or how to delete them.

Personally, I like persistent logins for the websites I visit on a regular basis, but I know how to handle them safely. If you are positive that your users know the same, you can use persistent logins with a clean conscience. If not - well, then you may subscribe to the philosophy that users who are careless with their login credentials brought it upon themselves if they get hacked. It's not like we go to our user's houses and tear off all those facepalm-inducing Post-It notes with passwords they have lined up on the edge of their monitors, either.

Of course, some systems can't afford to have any accounts hacked; for such systems, there is no way you can justify having persistent logins.

If you DO decide to implement persistent login cookies, this is how you do it:

  1. First, take some time to read Paragon Initiative's article on the subject. You'll need to get a bunch of elements right, and the article does a great job of explaining each.

  2. And just to reiterate one of the most common pitfalls, DO NOT STORE THE PERSISTENT LOGIN COOKIE (TOKEN) IN YOUR DATABASE, ONLY A HASH OF IT! The login token is Password Equivalent, so if an attacker got their hands on your database, they could use the tokens to log in to any account, just as if they were cleartext login-password combinations. Therefore, use hashing (according to https://security.stackexchange.com/a/63438/5002 a weak hash will do just fine for this purpose) when storing persistent login tokens.

PART III: Using Secret Questions

Don't implement 'secret questions'. The 'secret questions' feature is a security anti-pattern. Read the paper from link number 4 from the MUST-READ list. You can ask Sarah Palin about that one, after her Yahoo! email account got hacked during a previous presidential campaign because the answer to her security question was... "Wasilla High School"!

Even with user-specified questions, it is highly likely that most users will choose either:

  • A 'standard' secret question like mother's maiden name or favorite pet

  • A simple piece of trivia that anyone could lift from their blog, LinkedIn profile, or similar

  • Any question that is easier to answer than guessing their password. Which, for any decent password, is every question you can imagine

In conclusion, security questions are inherently insecure in virtually all their forms and variations, and should not be employed in an authentication scheme for any reason.

The true reason why security questions even exist in the wild is that they conveniently save the cost of a few support calls from users who can't access their email to get to a reactivation code. This at the expense of security and Sarah Palin's reputation. Worth it? Probably not.

PART IV: Forgotten Password Functionality

I already mentioned why you should never use security questions for handling forgotten/lost user passwords; it also goes without saying that you should never e-mail users their actual passwords. There are at least two more all-too-common pitfalls to avoid in this field:

  1. Don't reset a forgotten password to an autogenerated strong password - such passwords are notoriously hard to remember, which means the user must either change it or write it down - say, on a bright yellow Post-It on the edge of their monitor. Instead of setting a new password, just let users pick a new one right away - which is what they want to do anyway. (An exception to this might be if the users are universally using a password manager to store/manage passwords that would normally be impossible to remember without writing it down).

  2. Always hash the lost password code/token in the database. AGAIN, this code is another example of a Password Equivalent, so it MUST be hashed in case an attacker got their hands on your database. When a lost password code is requested, send the plaintext code to the user's email address, then hash it, save the hash in your database -- and throw away the original. Just like a password or a persistent login token.

A final note: always make sure your interface for entering the 'lost password code' is at least as secure as your login form itself, or an attacker will simply use this to gain access instead. Making sure you generate very long 'lost password codes' (for example, 16 case-sensitive alphanumeric characters) is a good start, but consider adding the same throttling scheme that you do for the login form itself.

PART V: Checking Password Strength

First, you'll want to read this small article for a reality check: The 500 most common passwords

Okay, so maybe the list isn't the canonical list of most common passwords on any system anywhere ever, but it's a good indication of how poorly people will choose their passwords when there is no enforced policy in place. Plus, the list looks frighteningly close to home when you compare it to publicly available analyses of recently stolen passwords.

So: With no minimum password strength requirements, 2% of users use one of the top 20 most common passwords. Meaning: if an attacker gets just 20 attempts, 1 in 50 accounts on your website will be crackable.

Thwarting this requires calculating the entropy of a password and then applying a threshold. The National Institute of Standards and Technology (NIST) Special Publication 800-63 has a set of very good suggestions. That, when combined with a dictionary and keyboard layout analysis (for example, 'qwertyuiop' is a bad password), can reject 99% of all poorly selected passwords at a level of 18 bits of entropy. Simply calculating password strength and showing a visual strength meter to a user is good, but insufficient. Unless it is enforced, a lot of users will most likely ignore it.

And for a refreshing take on user-friendliness of high-entropy passwords, Randall Munroe's Password Strength xkcd is highly recommended.

Utilize Troy Hunt's Have I Been Pwned API to check users passwords against passwords compromised in public data breaches.

PART VI: Much More - Or: Preventing Rapid-Fire Login Attempts

First, have a look at the numbers: Password Recovery Speeds - How long will your password stand up

If you don't have the time to look through the tables in that link, here's the list of them:

  1. It takes virtually no time to crack a weak password, even if you're cracking it with an abacus

  2. It takes virtually no time to crack an alphanumeric 9-character password if it is case insensitive

  3. It takes virtually no time to crack an intricate, symbols-and-letters-and-numbers, upper-and-lowercase password if it is less than 8 characters long (a desktop PC can search the entire keyspace up to 7 characters in a matter of days or even hours)

  4. It would, however, take an inordinate amount of time to crack even a 6-character password, if you were limited to one attempt per second!

So what can we learn from these numbers? Well, lots, but we can focus on the most important part: the fact that preventing large numbers of rapid-fire successive login attempts (ie. the brute force attack) really isn't that difficult. But preventing it right isn't as easy as it seems.

Generally speaking, you have three choices that are all effective against brute-force attacks (and dictionary attacks, but since you are already employing a strong passwords policy, they shouldn't be an issue):

  • Present a CAPTCHA after N failed attempts (annoying as hell and often ineffective -- but I'm repeating myself here)

  • Locking accounts and requiring email verification after N failed attempts (this is a DoS attack waiting to happen)

  • And finally, login throttling: that is, setting a time delay between attempts after N failed attempts (yes, DoS attacks are still possible, but at least they are far less likely and a lot more complicated to pull off).

Best practice #1: A short time delay that increases with the number of failed attempts, like:

  • 1 failed attempt = no delay
  • 2 failed attempts = 2 sec delay
  • 3 failed attempts = 4 sec delay
  • 4 failed attempts = 8 sec delay
  • 5 failed attempts = 16 sec delay
  • etc.

DoS attacking this scheme would be very impractical, since the resulting lockout time is slightly larger than the sum of the previous lockout times.

To clarify: The delay is not a delay before returning the response to the browser. It is more like a timeout or refractory period during which login attempts to a specific account or from a specific IP address will not be accepted or evaluated at all. That is, correct credentials will not return in a successful login, and incorrect credentials will not trigger a delay increase.

Best practice #2: A medium length time delay that goes into effect after N failed attempts, like:

  • 1-4 failed attempts = no delay
  • 5 failed attempts = 15-30 min delay

DoS attacking this scheme would be quite impractical, but certainly doable. Also, it might be relevant to note that such a long delay can be very annoying for a legitimate user. Forgetful users will dislike you.

Best practice #3: Combining the two approaches - either a fixed, short time delay that goes into effect after N failed attempts, like:

  • 1-4 failed attempts = no delay
  • 5+ failed attempts = 20 sec delay

Or, an increasing delay with a fixed upper bound, like:

  • 1 failed attempt = 5 sec delay
  • 2 failed attempts = 15 sec delay
  • 3+ failed attempts = 45 sec delay

This final scheme was taken from the OWASP best-practices suggestions (link 1 from the MUST-READ list) and should be considered best practice, even if it is admittedly on the restrictive side.

As a rule of thumb, however, I would say: the stronger your password policy is, the less you have to bug users with delays. If you require strong (case-sensitive alphanumerics + required numbers and symbols) 9+ character passwords, you could give the users 2-4 non-delayed password attempts before activating the throttling.

DoS attacking this final login throttling scheme would be very impractical. And as a final touch, always allow persistent (cookie) logins (and/or a CAPTCHA-verified login form) to pass through, so legitimate users won't even be delayed while the attack is in progress. That way, the very impractical DoS attack becomes an extremely impractical attack.

Additionally, it makes sense to do more aggressive throttling on admin accounts, since those are the most attractive entry points

PART VII: Distributed Brute Force Attacks

Just as an aside, more advanced attackers will try to circumvent login throttling by 'spreading their activities':

  • Distributing the attempts on a botnet to prevent IP address flagging

  • Rather than picking one user and trying the 50.000 most common passwords (which they can't, because of our throttling), they will pick THE most common password and try it against 50.000 users instead. That way, not only do they get around maximum-attempts measures like CAPTCHAs and login throttling, their chance of success increases as well, since the number 1 most common password is far more likely than number 49.995

  • Spacing the login requests for each user account, say, 30 seconds apart, to sneak under the radar

Here, the best practice would be logging the number of failed logins, system-wide, and using a running average of your site's bad-login frequency as the basis for an upper limit that you then impose on all users.

Too abstract? Let me rephrase:

Say your site has had an average of 120 bad logins per day over the past 3 months. Using that (running average), your system might set the global limit to 3 times that -- ie. 360 failed attempts over a 24 hour period. Then, if the total number of failed attempts across all accounts exceeds that number within one day (or even better, monitor the rate of acceleration and trigger on a calculated threshold), it activates system-wide login throttling - meaning short delays for ALL users (still, with the exception of cookie logins and/or backup CAPTCHA logins).

I also posted a question with more details and a really good discussion of how to avoid tricky pitfals in fending off distributed brute force attacks

PART VIII: Two-Factor Authentication and Authentication Providers

Credentials can be compromised, whether by exploits, passwords being written down and lost, laptops with keys being stolen, or users entering logins into phishing sites. Logins can be further protected with two-factor authentication, which uses out-of-band factors such as single-use codes received from a phone call, SMS message, app, or dongle. Several providers offer two-factor authentication services.

Authentication can be completely delegated to a single-sign-on service, where another provider handles collecting credentials. This pushes the problem to a trusted third party. Google and Twitter both provide standards-based SSO services, while Facebook provides a similar proprietary solution.

MUST-READ LINKS About Web Authentication

  1. OWASP Guide To Authentication / OWASP Authentication Cheat Sheet
  2. Dos and Don’ts of Client Authentication on the Web (very readable MIT research paper)
  3. Wikipedia: HTTP cookie
  4. Personal knowledge questions for fallback authentication: Security questions in the era of Facebook (very readable Berkeley research paper)

How to pass the password to su/sudo/ssh without overriding the TTY?

For sudo you can do this too:

sudo -S <<< "password" command

"Default Activity Not Found" on Android Studio upgrade

All answers above didn't help me. Try to remove this

<?xml version="1.0" encoding="utf-8"?>

in your AndroidManifest. Then:

File > Sync Project with Gradle Files

Strange Characters in database text: Ã, Ã, ¢, â‚ €,

This is surely an encoding problem. You have a different encoding in your database and in your website and this fact is the cause of the problem. Also if you ran that command you have to change the records that are already in your tables to convert those character in UTF-8.

Update: Based on your last comment, the core of the problem is that you have a database and a data source (the CSV file) which use different encoding. Hence you can convert your database in UTF-8 or, at least, when you get the data that are in the CSV, you have to convert them from UTF-8 to latin1.

You can do the convertion following this articles:

Connecting to a network folder with username/password in Powershell

At first glance one really wants to use New-PSDrive supplying it credentials.

> New-PSDrive -Name P -PSProvider FileSystem -Root \\server\share -Credential domain\user

Fails!

New-PSDrive : Cannot retrieve the dynamic parameters for the cmdlet. Dynamic parameters for NewDrive cannot be retrieved for the 'FileSystem' provider. The provider does not support the use of credentials. Please perform the operation again without specifying credentials.

The documentation states that you can provide a PSCredential object but if you look closer the cmdlet does not support this yet. Maybe in the next version I guess.

Therefore you can either use net use or the WScript.Network object, calling the MapNetworkDrive function:

$net = new-object -ComObject WScript.Network
$net.MapNetworkDrive("u:", "\\server\share", $false, "domain\user", "password")

Edit for New-PSDrive in PowerShell 3.0

Apparently with newer versions of PowerShell, the New-PSDrive cmdlet works to map network shares with credentials!

New-PSDrive -Name P -PSProvider FileSystem -Root \\Server01\Public -Credential user\domain -Persist

python: SyntaxError: EOL while scanning string literal

(Assuming you don't have/want line breaks in your string...)

How long is this string really?

I suspect there is a limit to how long a line read from a file or from the commandline can be, and because the end of the line gets choped off the parser sees something like s1="some very long string.......... (without an ending ") and thus throws a parsing error?

You can split long lines up in multiple lines by escaping linebreaks in your source like this:

s1="some very long string.....\
...\
...."

pandas groupby sort within groups

Here's other example of taking top 3 on sorted order, and sorting within the groups:

In [43]: import pandas as pd                                                                                                                                                       

In [44]:  df = pd.DataFrame({"name":["Foo", "Foo", "Baar", "Foo", "Baar", "Foo", "Baar", "Baar"], "count_1":[5,10,12,15,20,25,30,35], "count_2" :[100,150,100,25,250,300,400,500]})

In [45]: df                                                                                                                                                                        
Out[45]: 
   count_1  count_2  name
0        5      100   Foo
1       10      150   Foo
2       12      100  Baar
3       15       25   Foo
4       20      250  Baar
5       25      300   Foo
6       30      400  Baar
7       35      500  Baar


### Top 3 on sorted order:
In [46]: df.groupby(["name"])["count_1"].nlargest(3)                                                                                                                               
Out[46]: 
name   
Baar  7    35
      6    30
      4    20
Foo   5    25
      3    15
      1    10
dtype: int64


### Sorting within groups based on column "count_1":
In [48]: df.groupby(["name"]).apply(lambda x: x.sort_values(["count_1"], ascending = False)).reset_index(drop=True)
Out[48]: 
   count_1  count_2  name
0       35      500  Baar
1       30      400  Baar
2       20      250  Baar
3       12      100  Baar
4       25      300   Foo
5       15       25   Foo
6       10      150   Foo
7        5      100   Foo

IndexError: too many indices for array

I think the problem is given in the error message, although it is not very easy to spot:

IndexError: too many indices for array
xs  = data[:, col["l1"     ]]

'Too many indices' means you've given too many index values. You've given 2 values as you're expecting data to be a 2D array. Numpy is complaining because data is not 2D (it's either 1D or None).

This is a bit of a guess - I wonder if one of the filenames you pass to loadfile() points to an empty file, or a badly formatted one? If so, you might get an array returned that is either 1D, or even empty (np.array(None) does not throw an Error, so you would never know...). If you want to guard against this failure, you can insert some error checking into your loadfile function.

I highly recommend in your for loop inserting:

print(data)

This will work in Python 2.x or 3.x and might reveal the source of the issue. You might well find it is only one value of your outputs_l1 list (i.e. one file) that is giving the issue.

How to read files and stdout from a running Docker container

A bit late but this is what I'm doing with journald. It's pretty powerful.

You need to be running your docker containers on an OS with systemd-journald.

docker run -d --log-driver=journald myapp

This pipes the whole lot into host's journald which takes care of stuff like log pruning, storage format etc and gives you some cool options for viewing them:

journalctl CONTAINER_NAME=myapp -f

which will feed it to your console as it is logged,

journalctl CONTAINER_NAME=myapp > output.log

which gives you the whole lot in a file to take away, or

journalctl CONTAINER_NAME=myapp --since=17:45

Plus you can still see the logs via docker logs .... if that's your preference.

No more > my.log or -v "/apps/myapp/logs:/logs" etc

Pandas: Looking up the list of sheets in an excel file

from openpyxl import load_workbook

sheets = load_workbook(excel_file, read_only=True).sheetnames

For a 5MB Excel file I'm working with, load_workbook without the read_only flag took 8.24s. With the read_only flag it only took 39.6 ms. If you still want to use an Excel library and not drop to an xml solution, that's much faster than the methods that parse the whole file.

Retrieve column values of the selected row of a multicolumn Access listbox

For multicolumn listbox extract data from any column of selected row by

 listboxControl.List(listboxControl.ListIndex,col_num)

where col_num is required column ( 0 for first column)

Cloning git repo causes error - Host key verification failed. fatal: The remote end hung up unexpectedly

Resolved the issue... you need to add the ssh public key to your github account.

  1. Verify that the ssh keys have been setup correctly.
    1. Run ssh-keygen
    2. Enter the password (keep the default path - ~/.ssh/id_rsa)
  2. Add the public key (~/.ssh/id_rsa.pub) to github account
  3. Try git clone. It works!


Initial status (public key not added to git hub account)

foo@bn18-251:~$ rm -rf test
foo@bn18-251:~$ ls
foo@bn18-251:~$ git clone [email protected]:devendra-d-chavan/test.git
Cloning into 'test'...
Permission denied (publickey).
fatal: The remote end hung up unexpectedly
foo@bn18-251:~$


Now, add the public key ~/.ssh/id_rsa.pub to the github account (I used cat ~/.ssh/id_rsa.pub)

foo@bn18-251:~$ ssh-keygen 
Generating public/private rsa key pair.
Enter file in which to save the key (/home/foo/.ssh/id_rsa): 
Created directory '/home/foo/.ssh'.
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/foo/.ssh/id_rsa.
Your public key has been saved in /home/foo/.ssh/id_rsa.pub.
The key fingerprint is:
xxxxx
The key's randomart image is:
+--[ RSA 2048]----+
xxxxx
+-----------------+
foo@bn18-251:~$ cat ./.ssh/id_rsa.pub 
xxxxx
foo@bn18-251:~$ git clone [email protected]:devendra-d-chavan/test.git
Cloning into 'test'...
The authenticity of host 'github.com (207.97.227.239)' can't be established.
RSA key fingerprint is 16:27:ac:a5:76:28:2d:36:63:1b:56:4d:eb:df:a6:48.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'github.com,207.97.227.239' (RSA) to the list of known hosts.
Enter passphrase for key '/home/foo/.ssh/id_rsa': 
warning: You appear to have cloned an empty repository.
foo@bn18-251:~$ ls
test
foo@bn18-251:~/test$ git status
# On branch master
#
# Initial commit
#
nothing to commit (create/copy files and use "git add" to track)

How to configure Chrome's Java plugin so it uses an existing JDK in the machine

I use Windows 7 Professional 64-bit and have both the 32-bit and 64-bit Java 7u9 jre's installed. Chrome refused to work until I deleted the following registry key.

HKEY_LOCAL_MACHINE/Software/MozillaPlugins/@java.com/DTPlugin,version=10.9.2

Then I refreshed Chrome and the Applet loaded with a Warning that the plugin was out of date. I seleted "Run this time" and everything worked as expected.

There are two bugs related to this: 7118859 & 7133818

How to make HTML element resizable using pure Javascript?

_x000D_
_x000D_
// import
function get_difference(pre, mou) {
  return {
    x: mou.x - pre.x,
    y: mou.y - pre.y
  };
}

/*
if your panel is in a nested environment, which the parent container's width and height does not equa to document width 
and height, for example, in an element `canvas`, then edit it to

function oMousePos(e) {
  var rc = canvas.getBoundingClientRect();
  return {
    x: e.clientX - rc.left,
    y: e.clientY - rc.top,
  };
}
*/

function oMousePos(e) {
  return {
    x: e.clientX,
    y: e.clientY,
  };
}

function render_element(styles, el) {
  for (const [kk, vv] of Object.entries(styles)) {
    el.style[kk] = vv;
  }
}

class MoveablePanel {

  /*
  prevent an element from moving out of window
  */
  constructor(container, draggable, left, top) {
    this.container = container;
    this.draggable = draggable;
    this.left = left;
    this.top = top;
    let rect = container.getBoundingClientRect();
    this.width = rect.width;
    this.height = rect.height;
    this.status = false;

    // initial position of the panel, should not be changed
    this.original = {
      left: left,
      top: top
    };

    // current left and top postion
    // {this.left, this.top}

    // assign the panel to initial position
    // initalize in registration
    this.default();

    if (!MoveablePanel._instance) {
      MoveablePanel._instance = [];
    }
    MoveablePanel._instance.push(this);
  }

  mousedown(e) {
    this.status = true;
    this.previous = oMousePos(e)
  }

  mousemove(e) {
    if (!this.status) {
      return;
    }
    let pos = oMousePos(e);
    let vleft = this.left + pos.x - this.previous.x;
    let vtop = this.top + pos.y - this.previous.y;
    let kleft, ktop;

    if (vleft < 0) {
      kleft = 0;
    } else if (vleft > window.innerWidth - this.width) {
      kleft = window.innerWidth - this.width;
    } else {
      kleft = vleft;
    }

    if (vtop < 0) {
      ktop = 0;
    } else if (vtop > window.innerHeight - this.height) {
      ktop = window.innerHeight - this.height;
    } else {
      ktop = vtop;
    }
    this.container.style.left = `${kleft}px`;
    this.container.style.top = `${ktop}px`;
  }

  /*
  sometimes user move the cursor too fast which mouseleave is previous than mouseup
  to prevent moving too fast and break the control, mouseleave is handled the same as mouseup
  */

  mouseupleave(e) {
    if (!this.status) {
      return null;
    }
    this.status = false;
    let pos = oMousePos(e);
    let vleft = this.left + pos.x - this.previous.x;
    let vtop = this.top + pos.y - this.previous.y;

    if (vleft < 0) {
      this.left = 0;
    } else if (vleft > window.innerWidth - this.width) {
      this.left = window.innerWidth - this.width;
    } else {
      this.left = vleft;
    }

    if (vtop < 0) {
      this.top = 0;
    } else if (vtop > window.innerHeight - this.height) {
      this.top = window.innerHeight - this.height;
    } else {
      this.top = vtop;
    }

    this.show();
    return true;
  }

  default () {
    this.container.style.left = `${this.original.left}px`;
    this.container.style.top = `${this.original.top}px`;
  }

  /*
  panel with a higher z index will interupt drawing
  therefore if panel is not displaying, set it with a lower z index that canvas

  change index doesn't work, if panel is hiding, then we move it out
  hide: record current position, move panel out
  show: assign to recorded position

  notice this position has nothing to do panel drag movement
  they cannot share the same variable
  */

  hide() {
    // move to the right bottom conner
    this.container.style.left = `${window.screen.width}px`;
    this.container.style.top = `${window.screen.height}px`;
  }

  show() {
    this.container.style.left = `${this.left}px`;
    this.container.style.top = `${this.top}px`;
  }
}
// end of import

class DotButton{
    constructor(
        width_px, 
        styles, // mainly pos, padding and margin, e.g. {top: 0, left: 0, margin: 0},
        color, 
        color_hover,
        border, // boolean
        border_dismiss, // boolean: dismiss border when hover
    ){
        this.width = width_px;
        this.styles = styles;
        this.color = color;
        this.color_hover = color_hover;
        this.border = border;
        this.border_dismiss = border_dismiss;
    }

    create(_styles=null){
        var el = document.createElement('div');
        Object.keys(this.styles).forEach(kk=>{
            el.style[kk] = `${this.styles[kk]}px`;
        });
        if(_styles){
            Object.keys(_styles).forEach(kk=>{
                el.style[kk] = `${this.styles[kk]}px`;
            });
        }
        el.style.width = `${this.width}px`
        el.style.height = `${this.width}px`
        el.style.position = 'absolute';
        el.style.left = `${this.left_px}px`;
        el.style.top = `${this.top_px}px`;
        el.style.background = this.color;
        if(this.border){
            el.style.border = '1px solid'; 
        }
        el.style.borderRadius = `${this.width}px`;

        el.addEventListener('mouseenter', ()=>{
            el.style.background = this.color_hover;
            if(this.border_dismiss){
                el.style.border = `1px solid ${this.color_hover}`; 
            }
        });
        el.addEventListener('mouseleave', ()=>{
            el.style.background = this.color;
            if(this.border_dismiss){
                el.style.border = '1px solid'; 
            }
        });
        return el;
    }
}

function cursor_hover(el, default_cursor, to_cursor){
    el.addEventListener('mouseenter', function(){
        this.style.cursor = to_cursor;
    }.bind(el));


    el.addEventListener('mouseleave', function(){
        this.style.cursor = default_cursor;
    }.bind(el));
}

class FlexPanel extends MoveablePanel{
    constructor(
        parent_el,
        top_px,
        left_px,
        width_px, 
        height_px, 
        background,
        handle_width_px, 
        coner_vmin_ratio, 
        button_width_px, 
        button_margin_px, 
    ){
        super(
            (()=>{
                var el = document.createElement('div');
                render_element(
                    {
                        position: 'fixed', 
                        top: `${top_px}px`,
                        left: `${left_px}px`,
                        width: `${width_px}px`,
                        height: `${height_px}px`,
                        background: background, 
                    }, 
                    el,
                );
                return el;
            })(), // iife returns a container (panel el)
            new DotButton(button_width_px, {top: 0, right: 0, margin: button_margin_px}, 'green', 'lightgreen', false, false).create(), // draggable
            left_px, // left
            top_px, // top
        );

        this.draggable.addEventListener('mousedown', e => {
            e.preventDefault();
            this.mousedown(e);
        });

        this.draggable.addEventListener('mousemove', e => {
            e.preventDefault();
            this.mousemove(e);
        });

        this.draggable.addEventListener('mouseup', e => {
            e.preventDefault();
            this.mouseupleave(e);
        });

        this.draggable.addEventListener('mouseleave', e => {
            e.preventDefault();
            this.mouseupleave(e);
        });

        this.parent_el = parent_el;
        this.background = background;

        // parent
        this.width = width_px;
        this.height = height_px;

        this.handle_width_px = handle_width_px;
        this.coner_vmin_ratio = coner_vmin_ratio;

        this.panel_el = document.createElement('div');

        // styles that won't change 
        this.panel_el.style.position = 'absolute';
        this.panel_el.style.top = `${this.handle_width_px}px`;
        this.panel_el.style.left = `${this.handle_width_px}px`; 
        this.panel_el.style.background = this.background;
    
        this.handles = [
            this.handle_top,
            this.handle_left,
            this.handle_bottom,
            this.handle_right, 

            this.handle_lefttop,
            this.handle_topleft,
            this.handle_topright,
            this.handle_righttop, 
            this.handle_rightbottom, 
            this.handle_bottomright,
            this.handle_bottomleft,
            this.handle_leftbottom, 
        ] = Array.from({length: 12}, i => document.createElement('div'));

        this.handles.forEach(el=>{
            el.style.position = 'absolute';
        });

        this.handle_topleft.style.top = '0';
        this.handle_topleft.style.left = `${this.handle_width_px}px`;

        this.handle_righttop.style.right = '0';
        this.handle_righttop.style.top = `${this.handle_width_px}px`;

        this.handle_bottomright.style.bottom = '0';
        this.handle_bottomright.style.right = `${this.handle_width_px}px`;

        this.handle_leftbottom.style.left = '0';
        this.handle_leftbottom.style.bottom = `${this.handle_width_px}px`;


        this.handle_lefttop.style.left = '0';
        this.handle_lefttop.style.top = '0';

        this.handle_topright.style.top = '0';
        this.handle_topright.style.right = '0';

        this.handle_rightbottom.style.right = '0';
        this.handle_rightbottom.style.bottom = '0';

        this.handle_bottomleft.style.bottom = '0';
        this.handle_bottomleft.style.left = '0';

        this.update_ratio();

        [
            'ns-resize', // |
            'ew-resize', // -
            'ns-resize', // |
            'ew-resize', // -

            'nwse-resize', // \
            'nwse-resize', // \
            'nesw-resize', // /
            'nesw-resize', // /
            'nwse-resize', // \
            'nwse-resize', // \
            'nesw-resize', // /
            'nesw-resize', // /
        ].map((dd, ii)=>{
            cursor_hover(this.handles[ii], 'default', dd);
        });

        this.vtop = this.top;
        this.vleft = this.left;
        this.vwidth = this.width;
        this.vheight = this.height;

        this.update_ratio();

        this.handles.forEach(el=>{
            this.container.appendChild(el);
        });

        cursor_hover(this.draggable, 'default', 'move');

        this.panel_el.appendChild(this.draggable);
        this.container.appendChild(this.panel_el);
        this.parent_el.appendChild(this.container);

        [
            this.edgemousedown, 
            this.verticalmousemove,
            this.horizontalmousemove,
            this.nwsemousemove,
            this.neswmousemove,
            this.edgemouseupleave,
        ] = [
            this.edgemousedown.bind(this),
            this.verticalmousemove.bind(this),
            this.horizontalmousemove.bind(this),
            this.nwsemousemove.bind(this),
            this.neswmousemove.bind(this),
            this.edgemouseupleave.bind(this),
        ];

        this.handle_top.addEventListener('mousedown', e=>{this.edgemousedown(e, 'top')});
        this.handle_left.addEventListener('mousedown', e=>{this.edgemousedown(e, 'left')});
        this.handle_bottom.addEventListener('mousedown', e=>{this.edgemousedown(e, 'bottom')});
        this.handle_right.addEventListener('mousedown', e=>{this.edgemousedown(e, 'right')}); 
        this.handle_lefttop.addEventListener('mousedown', e=>{this.edgemousedown(e, 'lefttop')});
        this.handle_topleft.addEventListener('mousedown', e=>{this.edgemousedown(e, 'topleft')});
        this.handle_topright.addEventListener('mousedown', e=>{this.edgemousedown(e, 'topright')});
        this.handle_righttop.addEventListener('mousedown', e=>{this.edgemousedown(e, 'righttop')}); 
        this.handle_rightbottom.addEventListener('mousedown', e=>{this.edgemousedown(e, 'rightbottom')}); 
        this.handle_bottomright.addEventListener('mousedown', e=>{this.edgemousedown(e, 'bottomright')});
        this.handle_bottomleft.addEventListener('mousedown', e=>{this.edgemousedown(e, 'bottomleft')});
        this.handle_leftbottom.addEventListener('mousedown', e=>{this.edgemousedown(e, 'leftbottom')});

        this.handle_top.addEventListener('mousemove', this.verticalmousemove);
        this.handle_left.addEventListener('mousemove', this.horizontalmousemove);
        this.handle_bottom.addEventListener('mousemove', this.verticalmousemove);
        this.handle_right.addEventListener('mousemove', this.horizontalmousemove); 
        this.handle_lefttop.addEventListener('mousemove', this.nwsemousemove);
        this.handle_topleft.addEventListener('mousemove', this.nwsemousemove);
        this.handle_topright.addEventListener('mousemove', this.neswmousemove);
        this.handle_righttop.addEventListener('mousemove', this.neswmousemove); 
        this.handle_rightbottom.addEventListener('mousemove', this.nwsemousemove); 
        this.handle_bottomright.addEventListener('mousemove', this.nwsemousemove);
        this.handle_bottomleft.addEventListener('mousemove', this.neswmousemove);
        this.handle_leftbottom.addEventListener('mousemove', this.neswmousemove);

        this.handle_top.addEventListener('mouseup', e=>{this.verticalmousemove(e); this.edgemouseupleave()});
        this.handle_left.addEventListener('mouseup', e=>{this.horizontalmousemove(e); this.edgemouseupleave()});
        this.handle_bottom.addEventListener('mouseup', e=>{this.verticalmousemove(e); this.edgemouseupleave()});
        this.handle_right.addEventListener('mouseup', e=>{this.horizontalmousemove(e); this.edgemouseupleave()}); 
        this.handle_lefttop.addEventListener('mouseup', e=>{this.nwsemousemove(e); this.edgemouseupleave()});
        this.handle_topleft.addEventListener('mouseup', e=>{this.nwsemousemove(e); this.edgemouseupleave()});
        this.handle_topright.addEventListener('mouseup', e=>{this.neswmousemove(e); this.edgemouseupleave()});
        this.handle_righttop.addEventListener('mouseup', e=>{this.neswmousemove(e); this.edgemouseupleave()}); 
        this.handle_rightbottom.addEventListener('mouseup', e=>{this.nwsemousemove(e); this.edgemouseupleave()}); 
        this.handle_bottomright.addEventListener('mouseup', e=>{this.nwsemousemove(e); this.edgemouseupleave()});
        this.handle_bottomleft.addEventListener('mouseup', e=>{this.neswmousemove(e); this.edgemouseupleave()});
        this.handle_leftbottom.addEventListener('mouseup', e=>{this.neswmousemove(e); this.edgemouseupleave()});
    
        this.handle_top.addEventListener('mouseleave', this.edgemouseupleave);
        this.handle_left.addEventListener('mouseleave', this.edgemouseupleave);
        this.handle_bottom.addEventListener('mouseleave', this.edgemouseupleave);
        this.handle_right.addEventListener('mouseleave', this.edgemouseupleave);
        this.handle_lefttop.addEventListener('mouseleave', this.edgemouseupleave);
        this.handle_topleft.addEventListener('mouseleave', this.edgemouseupleave);
        this.handle_topright.addEventListener('mouseleave', this.edgemouseupleave);
        this.handle_righttop.addEventListener('mouseleave', this.edgemouseupleave);
        this.handle_rightbottom.addEventListener('mouseleave', this.edgemouseupleave);
        this.handle_bottomright.addEventListener('mouseleave', this.edgemouseupleave);
        this.handle_bottomleft.addEventListener('mouseleave', this.edgemouseupleave);
        this.handle_leftbottom.addEventListener('mouseleave', this.edgemouseupleave);
    }

    // box size change triggers corner handler size change
    update_ratio(){
        this.container.style.top = `${this.vtop}px`;
        this.container.style.left = `${this.vleft}px`;
        this.container.style.width = `${this.vwidth}px`;
        this.container.style.height = `${this.vheight}px`;

        this.panel_el.style.width = `${this.vwidth - 2 * this.handle_width_px}px`;
        this.panel_el.style.height = `${this.vheight - 2 * this.handle_width_px}px`;

        this.ratio = this.vwidth < this.vheight ? this.coner_vmin_ratio * this.vwidth : this.coner_vmin_ratio * this.vheight;
        [
            this.handle_top,
            this.handle_bottom, 
        ].forEach(el=>{
            el.style.width = `${this.vwidth - 2 * this.ratio}px`;
            el.style.height = `${this.handle_width_px}px`;
        });

        [
            this.handle_left,
            this.handle_right, 
        ].forEach(el=>{
            el.style.height = `${this.vheight - 2 * this.ratio}px`;
            el.style.width = `${this.handle_width_px}px`;
        });

        this.handle_top.style.top = `0`;
        this.handle_top.style.left = `${this.ratio}px`;

        this.handle_left.style.top = `${this.ratio}px`;
        this.handle_left.style.left = `0`;

        this.handle_bottom.style.bottom = `0`;
        this.handle_bottom.style.right = `${this.ratio}px`;

        this.handle_right.style.bottom = `${this.ratio}px`;
        this.handle_right.style.right = `0`;

        [
            this.handle_topright,
            this.handle_bottomleft,
        ].forEach(el=>{
            el.style.width = `${this.ratio}px`;
            el.style.height = `${this.handle_width_px}px`;
        });

        [
            this.handle_lefttop,
            this.handle_rightbottom,
        ].forEach(el=>{
            el.style.width = `${this.handle_width_px}px`;
            el.style.height = `${this.ratio}px`;
        });

        [
            this.handle_topleft,
            this.handle_bottomright,
        ].forEach(el=>{
            el.style.width = `${this.ratio - this.handle_width_px}px`;
            el.style.height = `${this.handle_width_px}px`;
        });

        [
            this.handle_righttop,
            this.handle_leftbottom,
        ].forEach(el=>{
            el.style.height = `${this.handle_width_px}px`;
            el.style.width = `${this.ratio - this.handle_width_px}px`;
        });
    }

    edgemousedown(e, flag){
        this.previous = oMousePos(e);
        this.flag = flag;
        this.drag = true;
    }

    verticalmousemove(e){
        if(this.drag){
            // -
            this.mouse = oMousePos(e);
            var ydif = this.mouse.y - this.previous.y;
            switch(this.flag){
                case 'top':
                    this.vtop = this.top + ydif;
                    this.vheight = this.height - ydif;

                    this.vleft = this.left;
                    this.vwidth = this.width;
                break;

                case 'bottom':
                    this.vheight = this.height + ydif;

                    this.vtop = this.top;
                    this.vleft = this.left;
                    this.vwidth = this.width;
                break;
            }
            this.update_ratio();
        }
    }

    horizontalmousemove(e){
        if(this.drag){
            // |
            this.mouse = oMousePos(e);
            var xdif = this.mouse.x - this.previous.x;
            switch(this.flag){
                case 'left':
                    this.vleft = this.left + xdif;
                    this.vwidth = this.width - xdif;

                    this.vtop = this.top;
                    this.vheight = this.height;
                break;

                case 'right':
                    this.vwidth = this.width + xdif;
                
                    this.vtop = this.top;
                    this.vleft = this.left;
                    this.vheight = this.height;
                break;
            }
            this.update_ratio();
        }
    }

    nwsemousemove(e){
        if(this.drag){
            // \
            this.mouse = oMousePos(e);
            var ydif = this.mouse.y - this.previous.y;
            var xdif = this.mouse.x - this.previous.x;
            switch(this.flag){
                case 'topleft':
                    this.vleft = this.left + xdif;
                    this.vtop = this.top + ydif;
                    this.vwidth = this.width - xdif;
                    this.vheight = this.height - ydif;
                break;

                case 'lefttop':
                    this.vleft = this.left + xdif;
                    this.vtop = this.top + ydif;
                    this.vwidth = this.width - xdif;
                    this.vheight = this.height - ydif;
                break;

                case 'bottomright':
                    this.vwidth = this.width + xdif;
                    this.vheight = this.height + ydif;

                    this.vtop = this.top;
                    this.vleft = this.left;
                break;

                case 'rightbottom':
                    this.vwidth = this.width + xdif;
                    this.vheight = this.height + ydif;

                    this.vtop = this.top;
                    this.vleft = this.left;
                break;
            }
            this.update_ratio();
        }
    }

    neswmousemove(e){
        if(this.drag){
            // /
            this.mouse = oMousePos(e);
            var ydif = this.mouse.y - this.previous.y;
            var xdif = this.mouse.x - this.previous.x;
            switch(this.flag){
                case 'topright':
                    this.vtop = this.top + ydif;
                    this.vwidth = this.width + xdif;
                    this.vheight = this.height - ydif;

                    this.vleft = this.left;
                break;

                case 'righttop':
                    this.vtop = this.top + ydif;
                    this.vwidth = this.width + xdif;
                    this.vheight = this.height - ydif;

                    this.vleft = this.left;
                break;

                case 'bottomleft':
                    this.vleft = this.left + xdif;
                    this.vwidth = this.width - xdif;
                    this.vheight = this.height + ydif;

                    this.vtop = this.top;
                break;

                case 'leftbottom':
                    this.vleft = this.left + xdif;
                    this.vwidth = this.width - xdif;
                    this.vheight = this.height + ydif;

                    this.vtop = this.top;
                break;
            }
            this.update_ratio();
        }
    }

    edgemouseupleave(){
        this.drag = false;
        this.top = this.vtop;
        this.left = this.vleft;
        this.width = this.vwidth;
        this.height = this.vheight;
    }

    mouseupleave(e){
        if(super.mouseupleave(e)){
            this.vtop = this.top;
            this.vleft = this.left;         
        }
    }
}


var fp = new FlexPanel(
    document.body, // parent div container
    20, // top margin
    20, // left margin
    200, // width 
    150, // height
    'lightgrey', // background
    20, // handle height when horizontal; handle width when vertical
    0.2, // edge up and left resize bar width : top resize bar width = 1 : 5
    35, // green move button width and height
    2, // button margin
);

/*
this method creates an element for you
which you don't need to pass in a selected element

to manipuate dom element
fp.container -> entire panel
fp.panel_el -> inside panel
*/
_x000D_
_x000D_
_x000D_

Achieving functionalities fully requires a lot of hard coding. Please refer to the documentation, it will show you how to use each class as element.

Persist javascript variables across pages?

I would recommend you to give a look to this library:

I really like it, it supports a variety of storage backends (from cookies to HTML5 storage, Gears, Flash, and more...), its usage is really transparent, you don't have to know or care which backend is used the library will choose the right storage backend depending on the browser capabilities.

How to convert a Base64 string into a Bitmap image to show it in a ImageView?

I have tried all the solutions and this one worked for me

let temp = base64String.components(separatedBy: ",")
let dataDecoded : Data = Data(base64Encoded: temp[1], options: 
 .ignoreUnknownCharacters)!
let decodedimage = UIImage(data: dataDecoded)

yourImage.image = decodedimage

Raw_Input() Is Not Defined

For Python 3.x, use input(). For Python 2.x, use raw_input(). Don't forget you can add a prompt string in your input() call to create one less print statement. input("GUESS THAT NUMBER!").

SimpleDateFormat parsing date with 'Z' literal

The 'X' only works if partial seconds are not present: i.e. SimpleDateFormat pattern of

"yyyy-MM-dd'T'HH:mm:ssX"

Will correctly parse

"2008-01-31T00:00:00Z"

but

"yyyy-MM-dd'T'HH:mm:ss.SX"

Will NOT parse

"2008-01-31T00:00:00.000Z"

Sad but true, a date-time with partial seconds does not appear to be a valid ISO date: http://en.wikipedia.org/wiki/ISO_8601

Can't create handler inside thread that has not called Looper.prepare() inside AsyncTask for ProgressDialog

I had a hard time making this work too, the solution for me was to use both hyui and konstantin answers,

class ExampleTask extends AsyncTask<String, String, String> {

// Your onPreExecute method.

@Override
protected String doInBackground(String... params) {
    // Your code.
    if (condition_is_true) {
        this.publishProgress("Show the dialog");
    }
    return "Result";
}

@Override
protected void onProgressUpdate(String... values) {

    super.onProgressUpdate(values);
    YourActivity.this.runOnUiThread(new Runnable() {
       public void run() {
           alertDialog.show();
       }
     });
 }

}

String vs. StringBuilder

Yes, the performance difference is significant. See the KB article "How to improve string concatenation performance in Visual C#".

I have always tried to code for clarity first, and then optimize for performance later. That's much easier than doing it the other way around! However, having seen the enormous performance difference in my applications between the two, I now think about it a little more carefully.

Luckily, it's relatively straightforward to run performance analysis on your code to see where you're spending the time, and then to modify it to use StringBuilder where needed.

ImportError: No module named pip

I had a similar problem with virtualenv that had python3.8 while installing dependencies from requirements.txt file. I managed to get it to work by activating the virtualenv and then running the command python -m pip install -r requirements.txt and it worked.

SQL query for today's date minus two months

SELECT COUNT(1)
FROM FB
WHERE
    Dte BETWEEN CAST(YEAR(GETDATE()) AS VARCHAR(4)) + '-' + CAST(MONTH(DATEADD(month, -1, GETDATE())) AS VARCHAR(2)) + '-20 00:00:00'
        AND CAST(YEAR(GETDATE()) AS VARCHAR(4)) + '-' + CAST(MONTH(GETDATE()) AS VARCHAR(2)) + '-20 00:00:00'

What is The Rule of Three?

The law of the big three is as specified above.

An easy example, in plain English, of the kind of problem it solves:

Non default destructor

You allocated memory in your constructor and so you need to write a destructor to delete it. Otherwise you will cause a memory leak.

You might think that this is job done.

The problem will be, if a copy is made of your object, then the copy will point to the same memory as the original object.

Once, one of these deletes the memory in its destructor, the other will have a pointer to invalid memory (this is called a dangling pointer) when it tries to use it things are going to get hairy.

Therefore, you write a copy constructor so that it allocates new objects their own pieces of memory to destroy.

Assignment operator and copy constructor

You allocated memory in your constructor to a member pointer of your class. When you copy an object of this class the default assignment operator and copy constructor will copy the value of this member pointer to the new object.

This means that the new object and the old object will be pointing at the same piece of memory so when you change it in one object it will be changed for the other objerct too. If one object deletes this memory the other will carry on trying to use it - eek.

To resolve this you write your own version of the copy constructor and assignment operator. Your versions allocate separate memory to the new objects and copy across the values that the first pointer is pointing to rather than its address.

What is the best way to get all the divisors of a number?

I'm just going to add a slightly revised version of Anivarth's (as I believe it's the most pythonic) for future reference.

from math import sqrt

def divisors(n):
    divs = {1,n}
    for i in range(2,int(sqrt(n))+1):
        if n%i == 0:
            divs.update((i,n//i))
    return divs

Is there a way to access an iteration-counter in Java's for-each loop?

I'm afraid this isn't possible with foreach. But I can suggest you a simple old-styled for-loops:

    List<String> l = new ArrayList<String>();

    l.add("a");
    l.add("b");
    l.add("c");
    l.add("d");

    // the array
    String[] array = new String[l.size()];

    for(ListIterator<String> it =l.listIterator(); it.hasNext() ;)
    {
        array[it.nextIndex()] = it.next();
    }

Notice that, the List interface gives you access to it.nextIndex().

(edit)

To your changed example:

    for(ListIterator<String> it =l.listIterator(); it.hasNext() ;)
    {
        int i = it.nextIndex();
        doSomethingWith(it.next(), i);
    }

What is the difference between __str__ and __repr__?

__repr__: representation of python object usually eval will convert it back to that object

__str__: is whatever you think is that object in text form

e.g.

>>> s="""w'o"w"""
>>> repr(s)
'\'w\\\'o"w\''
>>> str(s)
'w\'o"w'
>>> eval(str(s))==s
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<string>", line 1
    w'o"w
       ^
SyntaxError: EOL while scanning single-quoted string
>>> eval(repr(s))==s
True

JavaScript hide/show element

Just create hide and show methods yourself for all elements, as follows

Element.prototype.hide = function() {
    this.style.display = 'none';
}
Element.prototype.show = function() {
    this.style.display = '';
}

After this you can use the methods with the usual element identifiers like in these examples:

document.getElementByTagName('div')[3].hide();
document.getElementById('thing').show();

or:

<img src="removeME.png" onclick="this.hide()">

Finding first and last index of some value in a list in Python

If you are searching for the index of the last occurrence of myvalue in mylist:

len(mylist) - mylist[::-1].index(myvalue) - 1

Dictionary of dictionaries in Python?

dictionary's setdefault is a good way to update an existing dict entry if it's there, or create a new one if it's not all in one go:

Looping style:

# This is our sample data
data = [("Milter", "Miller", 4), ("Milter", "Miler", 4), ("Milter", "Malter", 2)]

# dictionary we want for the result
dictionary = {}

# loop that makes it work
for realName, falseName, position in data:
    dictionary.setdefault(realName, {})[falseName] = position

dictionary now equals:

{'Milter': {'Malter': 2, 'Miler': 4, 'Miller': 4}}

get the titles of all open windows

http://pinvoke.net/default.aspx/user32.EnumDesktopWindows

There is an example of using user.dll's EnumWindow in C# to list all open windows.

Mocking a class: Mock() or patch()?

Key points which explain difference and provide guidance upon working with unittest.mock

  1. Use Mock if you want to replace some interface elements(passing args) of the object under test
  2. Use patch if you want to replace internal call to some objects and imported modules of the object under test
  3. Always provide spec from the object you are mocking
    • With patch you can always provide autospec
    • With Mock you can provide spec
    • Instead of Mock, you can use create_autospec, which intended to create Mock objects with specification.

In the question above the right answer would be to use Mock, or to be more precise create_autospec (because it will add spec to the mock methods of the class you are mocking), the defined spec on the mock will be helpful in case of an attempt to call method of the class which doesn't exists ( regardless signature), please see some

from unittest import TestCase
from unittest.mock import Mock, create_autospec, patch


class MyClass:
    
    @staticmethod
    def method(foo, bar):
        print(foo)


def something(some_class: MyClass):
    arg = 1
    # Would fail becuase of wrong parameters passed to methd.
    return some_class.method(arg)


def second(some_class: MyClass):
    arg = 1
    return some_class.unexisted_method(arg)


class TestSomethingTestCase(TestCase):
    def test_something_with_autospec(self):
        mock = create_autospec(MyClass)
        mock.method.return_value = True
        # Fails because of signature misuse.
        result = something(mock)
        self.assertTrue(result)
        self.assertTrue(mock.method.called)
    
    def test_something(self):
        mock = Mock()  # Note that Mock(spec=MyClass) will also pass, because signatures of mock don't have spec.
        mock.method.return_value = True
        
        result = something(mock)
        
        self.assertTrue(result)
        self.assertTrue(mock.method.called)
        
    def test_second_with_patch_autospec(self):
        with patch(f'{__name__}.MyClass', autospec=True) as mock:
            # Fails because of signature misuse.
            result = second(mock)
        self.assertTrue(result)
        self.assertTrue(mock.unexisted_method.called)


class TestSecondTestCase(TestCase):
    def test_second_with_autospec(self):
        mock = Mock(spec=MyClass)
        # Fails because of signature misuse.
        result = second(mock)
        self.assertTrue(result)
        self.assertTrue(mock.unexisted_method.called)
    
    def test_second_with_patch_autospec(self):
        with patch(f'{__name__}.MyClass', autospec=True) as mock:
            # Fails because of signature misuse.
            result = second(mock)
        self.assertTrue(result)
        self.assertTrue(mock.unexisted_method.called)
    
    def test_second(self):
        mock = Mock()
        mock.unexisted_method.return_value = True
        
        result = second(mock)
        
        self.assertTrue(result)
        self.assertTrue(mock.unexisted_method.called)

The test cases with defined spec used fail because methods called from something and second functions aren't complaint with MyClass, which means - they catch bugs, whereas default Mock will display.

As a side note there is one more option: use patch.object to mock just the class method which is called with.

The good use cases for patch would be the case when the class is used as inner part of function:

def something():
    arg = 1
    return MyClass.method(arg)

Then you will want to use patch as a decorator to mock the MyClass.

iterating through json object javascript

Here is my recursive approach:

function visit(object) {
    if (isIterable(object)) {
        forEachIn(object, function (accessor, child) {
            visit(child);
        });
    }
    else {
        var value = object;
        console.log(value);
    }
}

function forEachIn(iterable, functionRef) {
    for (var accessor in iterable) {
        functionRef(accessor, iterable[accessor]);
    }
}

function isIterable(element) {
    return isArray(element) || isObject(element);
}

function isArray(element) {
    return element.constructor == Array;
}

function isObject(element) {
    return element.constructor == Object;
}

Why doesn't Git ignore my specified file?

Another possible reasona few instances of git clients running at the same time. For example "git shell" + "GitHub Desktop", etc.


This happened to me, I was using "GitHub Desktop" as the main client and it was ignoring some new .gitignore settings: commit after commit:

  1. You commit something.
  2. Next, commit: it ignores .gitignore settings. Commit includes lots of temp files mentioned in the .gitignore.
  3. Clear git cache; check whether .gitignore is UTF8; remove files -> commit -> move files back; skip 1 commit – nothing helped.

Reason: the Visual Studio Code editor was running in the background with the same opened repository. VS Code has built-in git control, and this makes some conflicts.

Solution: double-check multiple, hidden git clients and use only one git client at once, especially while clearing git cache.

How to disable gradle 'offline mode' in android studio?

@mikepenz has the right one.

You could just hit SHIFT+COMMAND+A (if you're using OSX and 1.4 android studio) and enter OFFLINE in the search box.

Then you'll see what mike have shown you.

Just deselect offline.

how to release localhost from Error: listen EADDRINUSE

To kill node server first run this command in your terminal :

  1. top
  2. open another window then copy the server id from the previous window: PID number -9 kill so now you killed your node server try again to run your app.

What is the javascript filename naming convention?

There is no official, universal, convention for naming JavaScript files.

There are some various options:

  • scriptName.js
  • script-name.js
  • script_name.js

are all valid naming conventions, however I prefer the jQuery suggested naming convention (for jQuery plugins, although it works for any JS)

  • jquery.pluginname.js

The beauty to this naming convention is that it explicitly describes the global namespace pollution being added.

  • foo.js adds window.foo
  • foo.bar.js adds window.foo.bar

Because I left out versioning: it should come after the full name, preferably separated by a hyphen, with periods between major and minor versions:

  • foo-1.2.1.js
  • foo-1.2.2.js
  • ...
  • foo-2.1.24.js

create multiple tag docker image

How not to do it:

When building an image, you could also tag it this way.

docker build -t ubuntu:14.04 .

Then you build it again with another tag:

docker build -t ubuntu:latest .

If your Dockerfile makes good use of the cache, the same image should come out, and it effectively does the same as retagging the same image. If you do docker images then you will see that they have the same ID.

There's probably a case where this goes wrong though... But like @david-braun said, you can't create tags with Dockerfiles themselves, just with the docker command.

How to search for a string in an arraylist

Nowadays, Java 8 allows for a one-line functional solution that is cleaner, faster, and a whole lot simpler than the accepted solution:

List<String> list = new ArrayList<>();
list.add("behold");
list.add("bend");
list.add("bet");
list.add("bear");
list.add("beat");
list.add("become");
list.add("begin");

List<String> matches = list.stream().filter(it -> it.contains("bea")).collect(Collectors.toList());

System.out.println(matches); // [bear, beat]

And even easier in Kotlin:

val matches = list.filter { it.contains("bea") }

How to execute a bash command stored as a string with quotes and asterisk

To eliminate the need for the cmd variable, you can do this:

eval 'mysql AMORE -u root --password="password" -h localhost -e "select host from amoreconfig"'

Exit a Script On Error

If you put set -e in a script, the script will terminate as soon as any command inside it fails (i.e. as soon as any command returns a nonzero status). This doesn't let you write your own message, but often the failing command's own messages are enough.

The advantage of this approach is that it's automatic: you don't run the risk of forgetting to deal with an error case.

Commands whose status is tested by a conditional (such as if, && or ||) do not terminate the script (otherwise the conditional would be pointless). An idiom for the occasional command whose failure doesn't matter is command-that-may-fail || true. You can also turn set -e off for a part of the script with set +e.

How to insert close button in popover for Bootstrap

Put this in your title popover constructor...

'<button class="btn btn-danger btn-xs pull-right"
onclick="$(this).parent().parent().parent().hide()"><span class="glyphicon
glyphicon-remove"></span></button>some text'

...to get a small red 'x' button on top-right corner

//$('[data-toggle=popover]').popover({title:that string here})

uppercase first character in a variable with bash

first-letter-to-lower () {
        str="" 
        space=" " 
        for i in $@
        do
                if [ -z $(echo $i | grep "the\|of\|with" ) ]
                then
                        str=$str"$(echo ${i:0:1} | tr  '[A-Z]' '[a-z]')${i:1}$space" 
                else
                        str=$str${i}$space 
                fi
        done
        echo $str
}
first-letter-to-upper-xc () {
        v-first-letter-to-upper | xclip -selection clipboard
}
first-letter-to-upper () {
        str="" 
        space=" " 
        for i in $@
        do
                if [ -z $(echo $i | grep "the\|of\|with" ) ]
                then
                        str=$str"$(echo ${i:0:1} | tr  '[a-z]' '[A-Z]')${i:1}$space" 
                else
                        str=$str${i}$space 
                fi
        done
        echo $str
}

first-letter-to-lower-xc(){ v-first-letter-to-lower | xclip -selection clipboard }

How to use jquery $.post() method to submit form values

Yor $.post has no data. You need to pass the form data. You can use serialize() to post the form data. Try this

$("#post-btn").click(function(){
    $.post("process.php", $('#reg-form').serialize() ,function(data){
        alert(data);
    });
});

How to loop and render elements in React.js without an array of objects to map?

I'm using Object.keys(chars).map(...) to loop in render

// chars = {a:true, b:false, ..., z:false}

render() {
    return (
       <div>
        {chars && Object.keys(chars).map(function(char, idx) {
            return <span key={idx}>{char}</span>;
        }.bind(this))}
        "Some text value"
       </div>
    );
}

How to select some rows with specific rownames from a dataframe?

Assuming that you have a data frame called students, you can select individual rows or columns using the bracket syntax, like this:

  • students[1,2] would select row 1 and column 2, the result here would be a single cell.
  • students[1,] would select all of row 1, students[,2] would select all of column 2.

If you'd like to select multiple rows or columns, use a list of values, like this:

  • students[c(1,3,4),] would select rows 1, 3 and 4,
  • students[c("stu1", "stu2"),] would select rows named stu1 and stu2.

Hope I could help.

Oracle SQL Developer - tables cannot be seen

The answer about going under "Other Users" was close, but not nearly explicit enough, so I felt the need to add this answer, below.

In Oracle, it will only show you tables that belong to schemas (databases in MS SQL Server) that are owned by the account you are logged in with. If the account owns/has created nothing, you will see nothing, even if you have rights/permissions to everything in the database! (This is contrary to MS SQL Server Management Studio, where you can see anything you have rights on and the owner is always "dbo", barring some admin going in and changing it for some unforeseeable reason.)

The owner will be the only one who will see those tables under "Tables" in the tree. If you do not see them because you are not their owner, you will have to go under "Other Users" and expand each user until you find out who created/owns that schema, if you do not know it, already. It will not matter if your account has permissions to the tables or not, you still have to go under "Other Users" and find that user that owns it to see it, under "Tables"!

One thing that can help you: when you write queries, you actually specify in the nomenclature who that owner is, ex.

Select * from admin.mytable

indicates that "admin" is the user that owns it, so you go under "Other Users > Admin" and expand "Tables" and there it is.

How to set max width of an image in CSS

Try this

 div#ImageContainer { width: 600px; }
 #ImageContainer img{ max-width: 600px}

How to calculate date difference in JavaScript?

Expressions like "difference in days" are never as simple as they seem. If you have the following dates:

d1: 2011-10-15 23:59:00
d1: 2011-10-16 00:01:00

the difference in time is 2 minutes, should the "difference in days" be 1 or 0? Similar issues arise for any expression of the difference in months, years or whatever since years, months and days are of different lengths and different times (e.g. the day that daylight saving starts is 1 hour shorter than usual and two hours shorter than the day that it ends).

Here is a function for a difference in days that ignores the time, i.e. for the above dates it returns 1.

/*
   Get the number of days between two dates - not inclusive.

   "between" does not include the start date, so days
   between Thursday and Friday is one, Thursday to Saturday
   is two, and so on. Between Friday and the following Friday is 7.

   e.g. getDaysBetweenDates( 22-Jul-2011, 29-jul-2011) => 7.

   If want inclusive dates (e.g. leave from 1/1/2011 to 30/1/2011),
   use date prior to start date (i.e. 31/12/2010 to 30/1/2011).

   Only calculates whole days.

   Assumes d0 <= d1
*/
function getDaysBetweenDates(d0, d1) {

  var msPerDay = 8.64e7;

  // Copy dates so don't mess them up
  var x0 = new Date(d0);
  var x1 = new Date(d1);

  // Set to noon - avoid DST errors
  x0.setHours(12,0,0);
  x1.setHours(12,0,0);

  // Round to remove daylight saving errors
  return Math.round( (x1 - x0) / msPerDay );
}

This can be more concise:

_x000D_
_x000D_
/*  Return number of days between d0 and d1._x000D_
**  Returns positive if d0 < d1, otherwise negative._x000D_
**_x000D_
**  e.g. between 2000-02-28 and 2001-02-28 there are 366 days_x000D_
**       between 2015-12-28 and 2015-12-29 there is 1 day_x000D_
**       between 2015-12-28 23:59:59 and 2015-12-29 00:00:01 there is 1 day_x000D_
**       between 2015-12-28 00:00:01 and 2015-12-28 23:59:59 there are 0 days_x000D_
**        _x000D_
**  @param {Date} d0  - start date_x000D_
**  @param {Date} d1  - end date_x000D_
**  @returns {number} - whole number of days between d0 and d1_x000D_
**_x000D_
*/_x000D_
function daysDifference(d0, d1) {_x000D_
  var diff = new Date(+d1).setHours(12) - new Date(+d0).setHours(12);_x000D_
  return Math.round(diff/8.64e7);_x000D_
}_x000D_
_x000D_
// Simple formatter_x000D_
function formatDate(date){_x000D_
  return [date.getFullYear(),('0'+(date.getMonth()+1)).slice(-2),('0'+date.getDate()).slice(-2)].join('-');_x000D_
}_x000D_
_x000D_
// Examples_x000D_
[[new Date(2000,1,28), new Date(2001,1,28)],  // Leap year_x000D_
 [new Date(2001,1,28), new Date(2002,1,28)],  // Not leap year_x000D_
 [new Date(2017,0,1),  new Date(2017,1,1)] _x000D_
].forEach(function(dates) {_x000D_
  document.write('From ' + formatDate(dates[0]) + ' to ' + formatDate(dates[1]) +_x000D_
                 ' is ' + daysDifference(dates[0],dates[1]) + ' days<br>');_x000D_
});
_x000D_
_x000D_
_x000D_

Android - implementing startForeground for a service?

I'd start by completely filling in the Notification. Here is a sample project demonstrating the use of startForeground().

What are the most widely used C++ vector/matrix math/linear algebra libraries, and their cost and benefit tradeoffs?

So I'm a pretty critical person, and figure if I'm going to invest in a library, I'd better know what I'm getting myself into. I figure it's better to go heavy on the criticism and light on the flattery when scrutinizing; what's wrong with it has many more implications for the future than what's right. So I'm going to go overboard here a little bit to provide the kind of answer that would have helped me and I hope will help others who may journey down this path. Keep in mind that this is based on what little reviewing/testing I've done with these libs. Oh and I stole some of the positive description from Reed.

I'll mention up top that I went with GMTL despite it's idiosyncrasies because the Eigen2 unsafeness was too big of a downside. But I've recently learned that the next release of Eigen2 will contain defines that will shut off the alignment code, and make it safe. So I may switch over.

Update: I've switched to Eigen3. Despite it's idiosyncrasies, its scope and elegance are too hard to ignore, and the optimizations which make it unsafe can be turned off with a define.

Eigen2/Eigen3

Benefits: LGPL MPL2, Clean, well designed API, fairly easy to use. Seems to be well maintained with a vibrant community. Low memory overhead. High performance. Made for general linear algebra, but good geometric functionality available as well. All header lib, no linking required.

Idiocyncracies/downsides: (Some/all of these can be avoided by some defines that are available in the current development branch Eigen3)

  • Unsafe performance optimizations result in needing careful following of rules. Failure to follow rules causes crashes.
    • you simply cannot safely pass-by-value
    • use of Eigen types as members requires special allocator customization (or you crash)
    • use with stl container types and possibly other templates required special allocation customization (or you will crash)
    • certain compilers need special care to prevent crashes on function calls (GCC windows)

GMTL

Benefits: LGPL, Fairly Simple API, specifically designed for graphics engines. Includes many primitive types geared towards rendering (such as planes, AABB, quatenrions with multiple interpolation, etc) that aren't in any other packages. Very low memory overhead, quite fast, easy to use. All header based, no linking necessary.

Idiocyncracies/downsides:

  • API is quirky
    • what might be myVec.x() in another lib is only available via myVec[0] (Readability problem)
      • an array or stl::vector of points may cause you to do something like pointsList[0][0] to access the x component of the first point
    • in a naive attempt at optimization, removed cross(vec,vec) and replaced with makeCross(vec,vec,vec) when compiler eliminates unnecessary temps anyway
    • normal math operations don't return normal types unless you shut off some optimization features e.g.: vec1 - vec2 does not return a normal vector so length( vecA - vecB ) fails even though vecC = vecA - vecB works. You must wrap like: length( Vec( vecA - vecB ) )
    • operations on vectors are provided by external functions rather than members. This may require you to use the scope resolution everywhere since common symbol names may collide
    • you have to do
        length( makeCross( vecA, vecB ) )
      or
        gmtl::length( gmtl::makeCross( vecA, vecB ) )
      where otherwise you might try
        vecA.cross( vecB ).length()
  • not well maintained
    • still claimed as "beta"
    • documentation missing basic info like which headers are needed to use normal functionalty
      • Vec.h does not contain operations for Vectors, VecOps.h contains some, others are in Generate.h for example. cross(vec&,vec&,vec&) in VecOps.h, [make]cross(vec&,vec&) in Generate.h
  • immature/unstable API; still changing.
    • For example "cross" has moved from "VecOps.h" to "Generate.h", and then the name was changed to "makeCross". Documentation examples fail because still refer to old versions of functions that no-longer exist.

NT2

Can't tell because they seem to be more interested in the fractal image header of their web page than the content. Looks more like an academic project than a serious software project.

Latest release over 2 years ago.

Apparently no documentation in English though supposedly there is something in French somewhere.

Cant find a trace of a community around the project.

LAPACK & BLAS

Benefits: Old and mature.

Downsides:

  • old as dinosaurs with really crappy APIs

How can I programmatically invoke an onclick() event from a anchor tag while keeping the ‘this’ reference in the onclick function?

Granted, OP stated very similarly that this didn't work, but it did for me. Based on the notes in my source, it seems it was implemented around the time, or after, OP's post. Perhaps it's more standard now.

document.getElementsByName('MyElementsName')[0].click();

In my case, my button didn't have an ID. If your element has an id, preferably use the following (untested).

document.getElementById('MyElementsId').click();

I originally tried this method and it didn't work. After Googling I came back and realized my element was by name, and didn't have an ID. Double check you're calling the right attribute.

Source: https://developer.mozilla.org/en-US/docs/Web/API/HTMLElement/click

How to stop java process gracefully?

Thanks for you answers. Shutdown hooks seams like something that would work in my case. But I also bumped into the thing called Monitoring and Management beans:
http://java.sun.com/j2se/1.5.0/docs/guide/management/overview.html
That gives some nice possibilities, for remote monitoring, and manipulation of the java process. (Was introduced in Java 5)

did you register the component correctly? For recursive components, make sure to provide the "name" option

In my case it was the order of importing in index.js

/* /components/index.js */
import List from './list.vue';
import ListItem from './list-item.vue';

export {List, ListItem}

and if you use ListItem component inside of List component it will show this error as it is not correctly imported. Make sure that all dependency components are imported first in order.

jQuery $("#radioButton").change(...) not firing during de-selection

My problem was similar and this worked for me:

$('body').on('change', '.radioClassNameHere', function() { ...

How to put a jpg or png image into a button in HTML

You can style the button using CSS or use an image-input. Additionally you might use the button element which supports inline content.

<button type="submit"><img src="/path/to/image" alt="Submit"></button>

IO Error: The Network Adapter could not establish the connection

Another thing you might want to check that the listener.ora file matches the way you are trying to connect to the DB. If you were connecting via a localhost reference and your listener.ora file got changed from:

HOST = localhost

to

HOST = 192.168.XX.XX

then this can cause the error that you had unless you update your hosts file to accommodate for this. Someone might have made this change to allow for remote connections to the DB from other machines.

Styling input radio with css

Here is simple example of how you can do this.

Just replace the image file and you are done.

HTML Code

<input type="radio" id="r1" name="rr" />
<label for="r1"><span></span>Radio Button 1</label>
<p>
<input type="radio" id="r2" name="rr" />
<label for="r2"><span></span>Radio Button 2</label>

CSS

input[type="radio"] {
    display:none;
}

input[type="radio"] + label {
    color:#f2f2f2;
    font-family:Arial, sans-serif;
    font-size:14px;
}

input[type="radio"] + label span {
    display:inline-block;
    width:19px;
    height:19px;
    margin:-1px 4px 0 0;
    vertical-align:middle;
    background:url(check_radio_sheet.png) -38px top no-repeat;
    cursor:pointer;
}

input[type="radio"]:checked + label span {
    background:url(check_radio_sheet.png) -57px top no-repeat;
}

Working DEMO

How to solve Notice: Undefined index: id in C:\xampp\htdocs\invmgt\manufactured_goods\change.php on line 21

You are not getting value of $id=$_GET['id'];

And you are using it (before it gets initialised).

Use php's in built isset() function to check whether the variable is defied or not.

So, please update the line to:

$id = isset($_GET['id']) ? $_GET['id'] : '';

Change private static final field using Java reflection

Just saw that question on one of the interview question, if possible to change final variable with reflection or in runtime. Got really interested, so that what I became with:

 /**
 * @author Dmitrijs Lobanovskis
 * @since 03/03/2016.
 */
public class SomeClass {

    private final String str;

    SomeClass(){
        this.str = "This is the string that never changes!";
    }

    public String getStr() {
        return str;
    }

    @Override
    public String toString() {
        return "Class name: " + getClass() + " Value: " + getStr();
    }
}

Some simple class with final String variable. So in the main class import java.lang.reflect.Field;

/**
 * @author Dmitrijs Lobanovskis
 * @since 03/03/2016.
 */
public class Main {


    public static void main(String[] args) throws Exception{

        SomeClass someClass = new SomeClass();
        System.out.println(someClass);

        Field field = someClass.getClass().getDeclaredField("str");
        field.setAccessible(true);

        field.set(someClass, "There you are");

        System.out.println(someClass);
    }
}

The output will be as follows:

Class name: class SomeClass Value: This is the string that never changes!
Class name: class SomeClass Value: There you are

Process finished with exit code 0

According to documentation https://docs.oracle.com/javase/tutorial/reflect/member/fieldValues.html

How do I create a Linked List Data Structure in Java?

Java has a LinkedList implementation, that you might wanna check out. You can download the JDK and it's sources at java.sun.com.

Get raw POST body in Python Flask regardless of Content-Type header

request.data will be empty if request.headers["Content-Type"] is recognized as form data, which will be parsed into request.form. To get the raw data regardless of content type, use request.get_data().

request.data calls request.get_data(parse_form_data=True), which results in the different behavior for form data.

How to make MySQL table primary key auto increment with some prefix

I know it is late but I just want to share on what I have done for this. I'm not allowed to add another table or trigger so I need to generate it in a single query upon insert. For your case, can you try this query.

CREATE TABLE YOURTABLE(
IDNUMBER VARCHAR(7) NOT NULL PRIMARY KEY,
ENAME VARCHAR(30) not null
);

Perform a select and use this select query and save to the parameter @IDNUMBER

(SELECT IFNULL
     (CONCAT('LHPL',LPAD(
       (SUBSTRING_INDEX
        (MAX(`IDNUMBER`), 'LHPL',-1) + 1), 5, '0')), 'LHPL001')
    AS 'IDNUMBER' FROM YOURTABLE ORDER BY `IDNUMBER` ASC)

And then Insert query will be :

INSERT INTO YOURTABLE(IDNUMBER, ENAME) VALUES 
(@IDNUMBER, 'EMPLOYEE NAME');

The result will be the same as the other answer but the difference is, you will not need to create another table or trigger. I hope that I can help someone that have a same case as mine.

How do I execute a command and get the output of the command within C++ using POSIX?

Two possible approaches:

  1. I don't think popen() is part of the C++ standard (it's part of POSIX from memory), but it's available on every UNIX I've worked with (and you seem to be targeting UNIX since your command is ./some_command).

  2. On the off-chance that there is no popen(), you can use system("./some_command >/tmp/some_command.out");, then use the normal I/O functions to process the output file.

React: trigger onChange if input value is changing by state?

Try this code if state object has sub objects like this.state.class.fee. We can pass values using following code:

this.setState({ class: Object.assign({}, this.state.class, { [element]: value }) }

Warning: The method assertEquals from the type Assert is deprecated

this method also encounter a deprecate warning:

org.junit.Assert.assertEquals(float expected,float actual) //deprecated

It is because currently junit prefer a third parameter rather than just two float variables input.

The third parameter is delta:

public static void assertEquals(double expected,double actual,double delta) //replacement

this is mostly used to deal with inaccurate Floating point calculations

for more information, please refer this problem: Meaning of epsilon argument of assertEquals for double values

What are 'get' and 'set' in Swift?

The getting and setting of variables within classes refers to either retrieving ("getting") or altering ("setting") their contents.

Consider a variable members of a class family. Naturally, this variable would need to be an integer, since a family can never consist of two point something people.

So you would probably go ahead by defining the members variable like this:

class family {
   var members:Int
}

This, however, will give people using this class the possibility to set the number of family members to something like 0 or 1. And since there is no such thing as a family of 1 or 0, this is quite unfortunate.

This is where the getters and setters come in. This way you can decide for yourself how variables can be altered and what values they can receive, as well as deciding what content they return.

Returning to our family class, let's make sure nobody can set the members value to anything less than 2:

class family {
  var _members:Int = 2
  var members:Int {
   get {
     return _members
   }
   set (newVal) {
     if newVal >= 2 {
       _members = newVal
     } else {
       println('error: cannot have family with less than 2 members')
     }
   }
  }
}

Now we can access the members variable as before, by typing instanceOfFamily.members, and thanks to the setter function, we can also set it's value as before, by typing, for example: instanceOfFamily.members = 3. What has changed, however, is the fact that we cannot set this variable to anything smaller than 2 anymore.

Note the introduction of the _members variable, which is the actual variable to store the value that we set through the members setter function. The original members has now become a computed property, meaning that it only acts as an interface to deal with our actual variable.

How to group an array of objects by key

Here is a solution inspired from Collectors.groupingBy() in Java:

_x000D_
_x000D_
function groupingBy(list, keyMapper) {_x000D_
  return list.reduce((accummalatorMap, currentValue) => {_x000D_
    const key = keyMapper(currentValue);_x000D_
    if(!accummalatorMap.has(key)) {_x000D_
      accummalatorMap.set(key, [currentValue]);_x000D_
    } else {_x000D_
      accummalatorMap.set(key, accummalatorMap.get(key).push(currentValue));_x000D_
    }_x000D_
    return accummalatorMap;_x000D_
  }, new Map());_x000D_
}
_x000D_
_x000D_
_x000D_

This will give a Map object.

_x000D_
_x000D_
// Usage_x000D_
_x000D_
const carMakers = groupingBy(cars, car => car.make);
_x000D_
_x000D_
_x000D_

TypeError: expected str, bytes or os.PathLike object, not _io.BufferedReader

I think it has to do with your second element in storbinary. You are trying to open file, but it is already a pointer to the file you opened in line file = open(local_path,'rb'). So, try to use ftp.storbinary("STOR " + i, file).

Difference between "while" loop and "do while" loop

The difference is in when the condition gets evaluated. In a do..while loop, the condition is not evaluated until the end of each loop. That means that a do..while loop will always run at least once. In a while loop, the condition is evaluated at the start.

Here I assume that wdlen is evaluating to false (i.e., it's bigger than 1) at the beginning of the while loop, so the while loop never runs. In the do..while loop, it isn't checked until the end of the first loop, so you get the result you expect.

Where are Magento's log files located?

You can find them in /var/log within your root Magento installation

There will usually be two files by default, exception.log and system.log.

If the directories or files don't exist, create them and give them the correct permissions, then enable logging within Magento by going to System > Configuration > Developer > Log Settings > Enabled = Yes

How to change color of SVG image using CSS (jQuery SVG image replacement)?

Style

svg path {
    fill: #000;
}

Script

$(document).ready(function() {
    $('img[src$=".svg"]').each(function() {
        var $img = jQuery(this);
        var imgURL = $img.attr('src');
        var attributes = $img.prop("attributes");

        $.get(imgURL, function(data) {
            // Get the SVG tag, ignore the rest
            var $svg = jQuery(data).find('svg');

            // Remove any invalid XML tags
            $svg = $svg.removeAttr('xmlns:a');

            // Loop through IMG attributes and apply on SVG
            $.each(attributes, function() {
                $svg.attr(this.name, this.value);
            });

            // Replace IMG with SVG
            $img.replaceWith($svg);
        }, 'xml');
    });
});

Unable to merge dex

I agree with Chris-Jr. If you are using Firebase to embed your AdMob ads (or even if you are not) the play-services-analytics includes the play-services-ads even though you don't add that as a dependency. Google have obviously made a mistake in their 11.4.0 roll-out as the analytics is including version 10.0.1 of ads, not 11.4.0 (the mouse over hint in the gradle shows this).

I manually added compile 'com.google.android.gms:play-services-ads:11.4.0' at the top which worked, but only after I disabled Instant Run: http://stackoverflow.com/a/35169716/530047

So its either regress to 10.0.1 or add the ads and disable Instant Run. That's what I found if it helps any.

Google MAP API v3: Center & Zoom on displayed markers

I've also find this fix that zooms to fit all markers

LatLngList: an array of instances of latLng, for example:

// "map" is an instance of GMap3

var LatLngList = [
                     new google.maps.LatLng (52.537,-2.061), 
                     new google.maps.LatLng (52.564,-2.017)
                 ],
    latlngbounds = new google.maps.LatLngBounds();

LatLngList.forEach(function(latLng){
   latlngbounds.extend(latLng);
});

// or with ES6:
// for( var latLng of LatLngList)
//    latlngbounds.extend(latLng);

map.setCenter(latlngbounds.getCenter());
map.fitBounds(latlngbounds); 

How to find all links / pages on a website

function getalllinks($url) {
    $links = array();
    if ($fp = fopen($url, 'r')) {
        $content = '';
        while ($line = fread($fp, 1024)) {
            $content. = $line;
        }
    }
    $textLen = strlen($content);
    if ($textLen > 10) {
        $startPos = 0;
        $valid = true;
        while ($valid) {
            $spos = strpos($content, '<a ', $startPos);
            if ($spos < $startPos) $valid = false;
            $spos = strpos($content, 'href', $spos);
            $spos = strpos($content, '"', $spos) + 1;
            $epos = strpos($content, '"', $spos);
            $startPos = $epos;
            $link = substr($content, $spos, $epos - $spos);
            if (strpos($link, 'http://') !== false) $links[] = $link;
        }
    }
    return $links;
}

try this code....

TypeError: 'undefined' is not a function (evaluating '$(document)')

I would use this

(function ($) {
   $(document);
}(jQuery));

How to send Request payload to REST API in java?

I tried with a rest client.

Headers :

  • POST /r/gerrit/rpc/ChangeDetailService HTTP/1.1
  • Host: git.eclipse.org
  • User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:18.0) Gecko/20100101 Firefox/18.0
  • Accept: application/json
  • Accept-Language: null
  • Accept-Encoding: gzip,deflate,sdch
  • accept-charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
  • Content-Type: application/json; charset=UTF-8
  • Content-Length: 73
  • Connection: keep-alive

it works fine. I retrieve 200 OK with a good body.

Why do you set a status code in your request? and multiple declaration "Accept" with Accept:application/json,application/json,application/jsonrequest. just a statement is enough.

How to make flexbox items the same size?

Im no expert with flex but I got there by setting the basis to 50% for the two items i was dealing with. Grow to 1 and shrink to 0.

Inline styling: flex: '1 0 50%',

What causes the error "_pickle.UnpicklingError: invalid load key, ' '."?

pickling is recursive, not sequential. Thus, to pickle a list, pickle will start to pickle the containing list, then pickle the first element… diving into the first element and pickling dependencies and sub-elements until the first element is serialized. Then moves on to the next element of the list, and so on, until it finally finishes the list and finishes serializing the enclosing list. In short, it's hard to treat a recursive pickle as sequential, except for some special cases. It's better to use a smarter pattern on your dump, if you want to load in a special way.

The most common pickle, it to pickle everything with a single dump to a file -- but then you have to load everything at once with a single load. However, if you open a file handle and do multiple dump calls (e.g. one for each element of the list, or a tuple of selected elements), then your load will mirror that… you open the file handle and do multiple load calls until you have all the list elements and can reconstruct the list. It's still not easy to selectively load only certain list elements, however. To do that, you'd probably have to store your list elements as a dict (with the index of the element or chunk as the key) using a package like klepto, which can break up a pickled dict into several files transparently, and enables easy loading of specific elements.

Saving and loading multiple objects in pickle file?

How do I convert a C# List<string[]> to a Javascript array?

I would say it's more a problem of the way you're modeling your data. Instead of using string arrays for addresses, it would be much cleaner and easier to do something like this:

Create a class to represent your addresses, like this:

public class Address
{
    public string Address1 { get; set; }
    public string CityName { get; set; }
    public string StateCode { get; set; }
    public string ZipCode { get; set; }
}

Then in your view model, you can populate those addresses like this:

public class ViewModel
{
    public IList<Address> Addresses = new List<Address>();

    public void PopulateAddresses()
    {
        foreach(DataRow row in AddressTable.Rows)
        {
            Address address = new Address
                {
                    Address1 = row["Address1"].ToString(),
                    CityName = row["CityName"].ToString(),
                    StateCode = row["StateCode"].ToString(),
                    ZipCode = row["ZipCode"].ToString()
                };
            Addresses.Add(address);
        }

        lAddressGeocodeModel.Addresses = JsonConvert.SerializeObject(Addresses);
    }
}

Which will give you JSON that looks like this:

[{"Address1" : "123 Easy Street", "CityName": "New York", "StateCode": "NY", "ZipCode": "12345"}]

Pad a number with leading zeros in JavaScript

Not a lot of "slick" going on so far:

function pad(n, width, z) {
  z = z || '0';
  n = n + '';
  return n.length >= width ? n : new Array(width - n.length + 1).join(z) + n;
}

When you initialize an array with a number, it creates an array with the length set to that value so that the array appears to contain that many undefined elements. Though some Array instance methods skip array elements without values, .join() doesn't, or at least not completely; it treats them as if their value is the empty string. Thus you get a copy of the zero character (or whatever "z" is) between each of the array elements; that's why there's a + 1 in there.

Example usage:

pad(10, 4);      // 0010
pad(9, 4);       // 0009
pad(123, 4);     // 0123

pad(10, 4, '-'); // --10

Unable to connect to any of the specified mysql hosts. C# MySQL

I found the solution to my problem, I was having the same issue. Previously I had my connection string as this notice the port :3306 needs to be either attached to the server like that 127.0.0.1:3306 or removed from server like that Server=127.0.0.1;Port=3306 depending on your .NET environment:

"Server=127.0.0.1:3306;Uid=username;Pwd=password;Database=db;"

It was running fine until something happened which I am not sure exactly what it is, might be a recent update to my .NET application packages. It looks like format and spacing of the connection string is important. Anyways, the following format seems to be working for me:

"Server=127.0.0.1;Port=3306;Uid=username;Pwd=password;Database=db;"

Try either of the versions and see which one works for you.

Also I noticed that you are not using camel casing, this could be it. Make sure your property names are in capital casing like that

Server
Port
Uid
Pwd
Database

How can I read and parse CSV files in C++?

If you're using Visual Studio / MFC, the following solution may make your life easier. It supports both Unicode and MBCS, has comments, doesn't have dependencies other than CString, and works well enough for me. It doesn't support line breaks embedded within a quoted string, but I don't care so long as it doesn't crash in that case, which it doesn't.

The overall strategy is, handle quoted and empty strings as special cases, and use Tokenize for the rest. For quoted strings, the strategy is, find the real closing quote, keeping track of whether pairs of consecutive quotes were encountered. If they were, use Replace to convert the pairs to singles. No doubt there are more efficient methods but performance wasn't sufficiently critical in my case to justify further optimization.

class CParseCSV {
public:
// Construction
    CParseCSV(const CString& sLine);

// Attributes
    bool    GetString(CString& sDest);

protected:
    CString m_sLine;    // line to extract tokens from
    int     m_nLen;     // line length in characters
    int     m_iPos;     // index of current position
};

CParseCSV::CParseCSV(const CString& sLine) : m_sLine(sLine)
{
    m_nLen = m_sLine.GetLength();
    m_iPos = 0;
}

bool CParseCSV::GetString(CString& sDest)
{
    if (m_iPos < 0 || m_iPos > m_nLen)  // if position out of range
        return false;
    if (m_iPos == m_nLen) { // if at end of string
        sDest.Empty();  // return empty token
        m_iPos = -1;    // really done now
        return true;
    }
    if (m_sLine[m_iPos] == '\"') {  // if current char is double quote
        m_iPos++;   // advance to next char
        int iTokenStart = m_iPos;
        bool    bHasEmbeddedQuotes = false;
        while (m_iPos < m_nLen) {   // while more chars to parse
            if (m_sLine[m_iPos] == '\"') {  // if current char is double quote
                // if next char exists and is also double quote
                if (m_iPos < m_nLen - 1 && m_sLine[m_iPos + 1] == '\"') {
                    // found pair of consecutive double quotes
                    bHasEmbeddedQuotes = true;  // request conversion
                    m_iPos++;   // skip first quote in pair
                } else  // next char doesn't exist or is normal
                    break;  // found closing quote; exit loop
            }
            m_iPos++;   // advance to next char
        }
        sDest = m_sLine.Mid(iTokenStart, m_iPos - iTokenStart);
        if (bHasEmbeddedQuotes) // if string contains embedded quote pairs
            sDest.Replace(_T("\"\""), _T("\""));    // convert pairs to singles
        m_iPos += 2;    // skip closing quote and trailing delimiter if any
    } else if (m_sLine[m_iPos] == ',') {    // else if char is comma
        sDest.Empty();  // return empty token
        m_iPos++;   // advance to next char
    } else {    // else get next comma-delimited token
        sDest = m_sLine.Tokenize(_T(","), m_iPos);
    }
    return true;
}

// calling code should look something like this:

    CStdioFile  fIn(pszPath, CFile::modeRead);
    CString sLine, sToken;
    while (fIn.ReadString(sLine)) { // for each line of input file
        if (!sLine.IsEmpty()) { // ignore blank lines
            CParseCSV   csv(sLine);
            while (csv.GetString(sToken)) {
                // do something with sToken here
            }
        }
    }

How can you export the Visual Studio Code extension list?

For those that are wondering how to copy your extensions from Visual Studio Code to Visual Studio Code insiders, use this modification of Benny's answer:

code --list-extensions | xargs -L 1 echo code-insiders --install-extension

Python: OSError: [Errno 2] No such file or directory: ''

I had this error because I was providing a string of arguments to subprocess.call instead of an array of arguments. To prevent this, use shlex.split:

import shlex, subprocess
command_line = "ls -a"
args = shlex.split(command_line)
p = subprocess.Popen(args)

This action could not be completed. Try Again (-22421)

Just try exporting the iPA file and then upload that exported iPA file with application loader. It will solve your problem.

No connection could be made because the target machine actively refused it (PHP / WAMP)

You might need:

  • In wamp\bin\mysql\mysqlX.X.XX\my.ini find these lines:

    [client] ... port = 3308 ... [wampmysqld64] ... port = 3308

As you see, the port number is 3308. You should :

  • use that port in applications, like WordPress: define('DB_HOST', 'localhost:3308')

or

  • change it globally in wamp\bin\apache\apache2.X.XXX\bin\php.ini change mysqli.default_port = ... to 3308

Reactive forms - disabled attribute

I tried these in angular 7. It worked successfully.

this.form.controls['fromField'].reset();
if(condition){
      this.form.controls['fromField'].enable();
}
else{
      this.form.controls['fromField'].disable();
}

Reading output of a command into an array in Bash

The other answers will break if output of command contains spaces (which is rather frequent) or glob characters like *, ?, [...].

To get the output of a command in an array, with one line per element, there are essentially 3 ways:

  1. With Bash=4 use mapfile—it's the most efficient:

    mapfile -t my_array < <( my_command )
    
  2. Otherwise, a loop reading the output (slower, but safe):

    my_array=()
    while IFS= read -r line; do
        my_array+=( "$line" )
    done < <( my_command )
    
  3. As suggested by Charles Duffy in the comments (thanks!), the following might perform better than the loop method in number 2:

    IFS=$'\n' read -r -d '' -a my_array < <( my_command && printf '\0' )
    

    Please make sure you use exactly this form, i.e., make sure you have the following:

    • IFS=$'\n' on the same line as the read statement: this will only set the environment variable IFS for the read statement only. So it won't affect the rest of your script at all. The purpose of this variable is to tell read to break the stream at the EOL character \n.
    • -r: this is important. It tells read to not interpret the backslashes as escape sequences.
    • -d '': please note the space between the -d option and its argument ''. If you don't leave a space here, the '' will never be seen, as it will disappear in the quote removal step when Bash parses the statement. This tells read to stop reading at the nil byte. Some people write it as -d $'\0', but it is not really necessary. -d '' is better.
    • -a my_array tells read to populate the array my_array while reading the stream.
    • You must use the printf '\0' statement after my_command, so that read returns 0; it's actually not a big deal if you don't (you'll just get an return code 1, which is okay if you don't use set -e – which you shouldn't anyway), but just bear that in mind. It's cleaner and more semantically correct. Note that this is different from printf '', which doesn't output anything. printf '\0' prints a null byte, needed by read to happily stop reading there (remember the -d '' option?).

If you can, i.e., if you're sure your code will run on Bash=4, use the first method. And you can see it's shorter too.

If you want to use read, the loop (method 2) might have an advantage over method 3 if you want to do some processing as the lines are read: you have direct access to it (via the $line variable in the example I gave), and you also have access to the lines already read (via the array ${my_array[@]} in the example I gave).

Note that mapfile provides a way to have a callback eval'd on each line read, and in fact you can even tell it to only call this callback every N lines read; have a look at help mapfile and the options -C and -c therein. (My opinion about this is that it's a little bit clunky, but can be used sometimes if you only have simple things to do — I don't really understand why this was even implemented in the first place!).


Now I'm going to tell you why the following method:

my_array=( $( my_command) )

is broken when there are spaces:

$ # I'm using this command to test:
$ echo "one two"; echo "three four"
one two
three four
$ # Now I'm going to use the broken method:
$ my_array=( $( echo "one two"; echo "three four" ) )
$ declare -p my_array
declare -a my_array='([0]="one" [1]="two" [2]="three" [3]="four")'
$ # As you can see, the fields are not the lines
$
$ # Now look at the correct method:
$ mapfile -t my_array < <(echo "one two"; echo "three four")
$ declare -p my_array
declare -a my_array='([0]="one two" [1]="three four")'
$ # Good!

Then some people will then recommend using IFS=$'\n' to fix it:

$ IFS=$'\n'
$ my_array=( $(echo "one two"; echo "three four") )
$ declare -p my_array
declare -a my_array='([0]="one two" [1]="three four")'
$ # It works!

But now let's use another command, with globs:

$ echo "* one two"; echo "[three four]"
* one two
[three four]
$ IFS=$'\n'
$ my_array=( $(echo "* one two"; echo "[three four]") )
$ declare -p my_array
declare -a my_array='([0]="* one two" [1]="t")'
$ # What?

That's because I have a file called t in the current directory… and this filename is matched by the glob [three four]… at this point some people would recommend using set -f to disable globbing: but look at it: you have to change IFS and use set -f to be able to fix a broken technique (and you're not even fixing it really)! when doing that we're really fighting against the shell, not working with the shell.

$ mapfile -t my_array < <( echo "* one two"; echo "[three four]")
$ declare -p my_array
declare -a my_array='([0]="* one two" [1]="[three four]")'

here we're working with the shell!

Call a function from another file?

First save the file in .py format (for example, my_example.py). And if that file have functions,

def xyz():

        --------

        --------

def abc():

        --------

        --------

In the calling function you just have to type the below lines.

file_name: my_example2.py

============================

import my_example.py


a = my_example.xyz()

b = my_example.abc()

============================

How do I make an HTML text box show a hint when empty?

I found the jQuery plugin jQuery Watermark to be better than the one listed in the top answer. Why better? Because it supports password input fields. Also, setting the color of the watermark (or other attributes) is as easy as creating a .watermark reference in your CSS file.

How to iterate object in JavaScript?

Using a generator function you could iterate over deep key-values.

_x000D_
_x000D_
function * deepEntries(obj) { _x000D_
    for(let [key, value] of Object.entries(obj)) {_x000D_
        if (typeof value !== 'object') _x000D_
            yield [key, value]_x000D_
        else _x000D_
            for(let entries of deepEntries(value))_x000D_
                yield [key, ...entries]_x000D_
    }_x000D_
}_x000D_
_x000D_
const dictionary = {_x000D_
    "data": [_x000D_
        {"id":"0","name":"ABC"},_x000D_
        {"id":"1","name":"DEF"}_x000D_
    ],_x000D_
    "images": [_x000D_
        {"id":"0","name":"PQR"},_x000D_
        {"id":"1","name":"xyz"}_x000D_
    ]_x000D_
}_x000D_
_x000D_
for(let entries of deepEntries(dictionary)) {_x000D_
    const key = entries.slice(0, -1).join('.')_x000D_
    const value = entries[entries.length-1]_x000D_
    console.log(key, value)_x000D_
}
_x000D_
_x000D_
_x000D_

How to start automatic download of a file in Internet Explorer?

I checked and found, it will work on button click via writing onclick event to Anchor tag or Input button

onclick='javascript:setTimeout(window.location=[File location], 1000);'

Replace Multiple String Elements in C#

Quicker - no. More effective - yes, if you will use the StringBuilder class. With your implementation each operation generates a copy of a string which under circumstances may impair performance. Strings are immutable objects so each operation just returns a modified copy.

If you expect this method to be actively called on multiple Strings of significant length, it might be better to "migrate" its implementation onto the StringBuilder class. With it any modification is performed directly on that instance, so you spare unnecessary copy operations.

public static class StringExtention
{
    public static string clean(this string s)
    {
        StringBuilder sb = new StringBuilder (s);

        sb.Replace("&", "and");
        sb.Replace(",", "");
        sb.Replace("  ", " ");
        sb.Replace(" ", "-");
        sb.Replace("'", "");
        sb.Replace(".", "");
        sb.Replace("eacute;", "é");

        return sb.ToString().ToLower();
    }
}

Environment variable substitution in sed

VAR=8675309
echo "abcde:jhdfj$jhbsfiy/.hghi$jh:12345:dgve::" |\
sed 's/:[0-9]*:/:'$VAR':/1' 

where VAR contains what you want to replace the field with

calling Jquery function from javascript

jQuery functions are called just like JavaScript functions.

For example, to dynamically add the class "red" to the document element with the id "orderedlist" using the jQuery addClass function:

$("#orderedlist").addClass("red");

As opposed to a regular line of JavaScript calling a regular function:

var x = document.getElementById("orderedlist");

addClass() is a jQuery function, getElementById() is a JavaScript function.

The dollar sign function makes the jQuery addClass function available.

The only difference is the jQuery example is calling the addclass function of the jQuery object $("#orderedlist") and the regular example is calling a function of the document object.

In your code

$(function() {
// code to execute when the DOM is ready
});

Is used to specify code to run when the DOM is ready.

It does not differentiate (as you may think) what is "jQuery code" from regular JavaScript code.

So, to answer your question, just call functions you defined as you normally would.

//create a function
function my_fun(){
  // call a jQuery function:
  $("#orderedlist").addClass("red");
}

//call the function you defined:
myfun();

Insertion sort vs Bubble Sort Algorithms

Another difference, I didn't see here:

Bubble sort has 3 value assignments per swap: you have to build a temporary variable first to save the value you want to push forward(no.1), than you have to write the other swap-variable into the spot you just saved the value of(no.2) and then you have to write your temporary variable in the spot other spot(no.3). You have to do that for each spot - you want to go forward - to sort your variable to the correct spot.

With insertion sort you put your variable to sort in a temporary variable and then put all variables in front of that spot 1 spot backwards, as long as you reach the correct spot for your variable. That makes 1 value assignement per spot. In the end you write your temp-variable into the the spot.

That makes far less value assignements, too.

This isn't the strongest speed-benefit, but i think it can be mentioned.

I hope, I expressed myself understandable, if not, sorry, I'm not a nativ Britain

Convert unsigned int to signed int C

You are expecting that your int type is 16 bit wide, in which case you'd indeed get a negative value. But most likely it's 32 bits wide, so a signed int can represent 65529 just fine. You can check this by printing sizeof(int).

java.sql.SQLException Parameter index out of range (1 > number of parameters, which is 0)

You will get this error when you call any of the setXxx() methods on PreparedStatement, while the SQL query string does not have any placeholders ? for this.

For example this is wrong:

String sql = "INSERT INTO tablename (col1, col2, col3) VALUES (val1, val2, val3)";
// ...

preparedStatement = connection.prepareStatement(sql);
preparedStatement.setString(1, val1); // Fail.
preparedStatement.setString(2, val2);
preparedStatement.setString(3, val3);

You need to fix the SQL query string accordingly to specify the placeholders.

String sql = "INSERT INTO tablename (col1, col2, col3) VALUES (?, ?, ?)";
// ...

preparedStatement = connection.prepareStatement(sql);
preparedStatement.setString(1, val1);
preparedStatement.setString(2, val2);
preparedStatement.setString(3, val3);

Note the parameter index starts with 1 and that you do not need to quote those placeholders like so:

String sql = "INSERT INTO tablename (col1, col2, col3) VALUES ('?', '?', '?')";

Otherwise you will still get the same exception, because the SQL parser will then interpret them as the actual string values and thus can't find the placeholders anymore.

See also:

Removing cordova plugins from the project

You can do it with bash as well (after switching to your Cordova project directory):

for i in `cordova plugin ls | grep '^[^ ]*' -o`; do cordova plugin rm $i; done

MongoDB: update every document on one field

Regardless of the version, for your example, the <update> is:

{  $set: { lastLookedAt: Date.now() / 1000 }  }

However, depending on your version of MongoDB, the query will look different. Regardless of version, the key is that the empty condition {} will match any document. In the Mongo shell, or with any MongoDB client:

$version >= 3.2:

db.foo.updateMany( {}, <update> )
  • {} is the condition (the empty condition matches any document)

3.2 > $version >= 2.2:

db.foo.update( {}, <update>, { multi: true } )
  • {} is the condition (the empty condition matches any document)
  • {multi: true} is the "update multiple documents" option

$version < 2.2:

db.foo.update( {}, <update>, false, true )
  • {} is the condition (the empty condition matches any document)
  • false is for the "upsert" parameter
  • true is for the "multi" parameter (update multiple records)

PHP - print all properties of an object

for knowing the object properties var_dump(object) is the best way. It will show all public, private and protected properties associated with it without knowing the class name.

But in case of methods, you need to know the class name else i think it's difficult to get all associated methods of the object.

restrict edittext to single line

android:maxLines="1"
android:inputType="text"

Add the above code to have a single line in EditText tag in your layout.

android:singleLine="true" is deprecated

This constant was deprecated in API level 3.

This attribute is deprecated. Use maxLines instead to change the layout of a static text, and use the textMultiLine flag in the inputType attribute instead for editable text views (if both singleLine and inputType are supplied, the inputType flags will override the value of singleLine).

Can a local variable's memory be accessed outside its scope?

Did you compile your program with the optimiser enabled? The foo() function is quite simple and might have been inlined or replaced in the resulting code.

But I agree with Mark B that the resulting behavior is undefined.

How can I change the text color with jQuery?

Place the following in your jQuery mouseover event handler:

$(this).css('color', 'red');

To set both color and size at the same time:

$(this).css({ 'color': 'red', 'font-size': '150%' });

You can set any CSS attribute using the .css() jQuery function.

How to modify JsonNode in Java?

You need to get ObjectNode type object in order to set values. Take a look at this

How to add new item to hash

It's as simple as:

irb(main):001:0> hash = {:item1 => 1}
=> {:item1=>1}
irb(main):002:0> hash[:item2] = 2
=> 2
irb(main):003:0> hash
=> {:item1=>1, :item2=>2}

Can we locate a user via user's phone number in Android?

Quick answer: No, at least not with native SMS service.

Long answer: Sure, but the receiver's phone should have the correct setup first. An app that detects incoming sms, and if a keyword matches, reports its current location to your server, which then pushes that info to the sender.

receiver type *** for instance message is a forward declaration

I was trying to use @class "Myclass.h".

When I changed it to #import "Myclass.h", it worked fine.

Can I set a TTL for @Cacheable

See http://static.springsource.org/spring/docs/3.1.x/spring-framework-reference/htmlsingle/spring-framework-reference.html#cache-specific-config:

How can I set the TTL/TTI/Eviction policy/XXX feature?

Directly through your cache provider. The cache abstraction is... well, an abstraction not a cache implementation

So, if you use EHCache, use EHCache's configuration to configure the TTL.

You could also use Guava's CacheBuilder to build a cache, and pass this cache's ConcurrentMap view to the setStore method of the ConcurrentMapCacheFactoryBean.

cannot download, $GOPATH not set

This problem occured to me in raspberry pi. I had logged in through VNC client The problem persisted despite setting and exporting the GOPATH. Then Ran the "go get" command without sudo and it worked perfectly.

Import python package from local directory into interpreter

If you want to run an unmodified python script so it imports libraries from a specific local directory you can set the PYTHONPATH environment variable - e.g. in bash:

export PYTHONPATH=/home/user/my_libs
python myscript.py

If you just want it to import from the current working directory use the . notation:

export PYTHONPATH=.
python myscript.py

how to overwrite css style

Increase your CSS Specificity

Example:

.parent-class .flex-control-thumbs li {
  width: auto;
  float: none;
}

Demo:

_x000D_
_x000D_
.sample-class {
  height: 50px;
  width: 50px;
  background: red;
}

.inner-page .sample-class {
  background: green;
}
_x000D_
<div>
  <div class="sample-class"></div>
</div>

<div class="inner-page">
  <div class="sample-class"></div>
</div>
_x000D_
_x000D_
_x000D_

How can I detect Internet Explorer (IE) and Microsoft Edge using JavaScript?

// detect IE8 and above, and Edge
if (document.documentMode || /Edge/.test(navigator.userAgent)) {
    ... do something
}

Explanation:

document.documentMode

An IE only property, first available in IE8.

/Edge/

A regular expression to search for the string 'Edge' - which we then test against the 'navigator.userAgent' property

Update Mar 2020

@Jam comments that the latest version of Edge now reports Edg as the user agent. So the check would be:

if (document.documentMode || /Edge/.test(navigator.userAgent) || /Edg/.test(navigator.userAgent)) {
    ... do something
}

How to solve SQL Server Error 1222 i.e Unlock a SQL Server table

In the SQL Server Management Studio, to find out details of the active transaction, execute following command

DBCC opentran()

You will get the detail of the active transaction, then from the SPID of the active transaction, get the detail about the SPID using following commands

exec sp_who2 <SPID>
exec sp_lock <SPID>

For example, if SPID is 69 then execute the command as

exec sp_who2 69
exec sp_lock 69

Now , you can kill that process using the following command

KILL 69

I hope this helps :)

Extract part of a regex match

Use ( ) in regexp and group(1) in python to retrieve the captured string (re.search will return None if it doesn't find the result, so don't use group() directly):

title_search = re.search('<title>(.*)</title>', html, re.IGNORECASE)

if title_search:
    title = title_search.group(1)

Display all dataframe columns in a Jupyter Python Notebook

Try the display max_columns setting as follows:

import pandas as pd
from IPython.display import display

df = pd.read_csv("some_data.csv")
pd.options.display.max_columns = None
display(df)

Or

pd.set_option('display.max_columns', None)

Edit: Pandas 0.11.0 backwards

This is deprecated but in versions of Pandas older than 0.11.0 the max_columns setting is specified as follows:

pd.set_printoptions(max_columns=500)

Java 8 Lambda function that throws exception?

Another solution using a Function wrapper would be to return either an instance of a wrapper of your result, say Success, if everything went well, either an instance of, say Failure.

Some code to clarify things :

public interface ThrowableFunction<A, B> {
    B apply(A a) throws Exception;
}

public abstract class Try<A> {

    public static boolean isSuccess(Try tryy) {
        return tryy instanceof Success;
    }

    public static <A, B> Function<A, Try<B>> tryOf(ThrowableFunction<A, B> function) {
        return a -> {
            try {
                B result = function.apply(a);
                return new Success<B>(result);
            } catch (Exception e) {
                return new Failure<>(e);
            }
        };
    }

    public abstract boolean isSuccess();

    public boolean isError() {
        return !isSuccess();
    }

    public abstract A getResult();

    public abstract Exception getError();
}

public class Success<A> extends Try<A> {

    private final A result;

    public Success(A result) {
        this.result = result;
    }

    @Override
    public boolean isSuccess() {
        return true;
    }

    @Override
    public A getResult() {
        return result;
    }

    @Override
    public Exception getError() {
        return new UnsupportedOperationException();
    }

    @Override
    public boolean equals(Object that) {
        if(!(that instanceof Success)) {
            return false;
        }
        return Objects.equal(result, ((Success) that).getResult());
    }
}

public class Failure<A> extends Try<A> {

    private final Exception exception;

    public Failure(Exception exception) {
        this.exception = exception;
    }

    @Override
    public boolean isSuccess() {
        return false;
    }

    @Override
    public A getResult() {
        throw new UnsupportedOperationException();
    }

    @Override
    public Exception getError() {
        return exception;
    }
}

A simple use case :

List<Try<Integer>> result = Lists.newArrayList(1, 2, 3).stream().
    map(Try.<Integer, Integer>tryOf(i -> someMethodThrowingAnException(i))).
    collect(Collectors.toList());

What does getActivity() mean?

Two likely definitions:

Amazon products API - Looking for basic overview and information

I wrote a blog post on this subject, after spending hours wading through Amazon's obscure documentation. Maybe useful as another view on the process.

Android: Create a toggle button with image and no text

I know this is a little late, however for anyone interested, I've created a custom component that is basically a toggle image button, the drawable can have states as well as the background

https://gist.github.com/akshaydashrath/9662072

iOS 7 App Icons, Launch images And Naming Convention While Keeping iOS 6 Icons

In case you do not want to use Asset Catalog, you can add an iOS 7 icon for an old app by creating a 120x120 .png image. Name it Icon-120.png and drag in to the project.

Under TARGET > Your App > Info > Icon files, add one more entry in the Target Properties:

enter image description here

I tested on Xcode 5 and an app was submitted without the missing retina icon warning.

Force GUI update from UI Thread

After updating the UI, start a task to perform with the long running operation:

label.Text = "Please Wait...";

Task<string> task = Task<string>.Factory.StartNew(() =>
{
    try
    {
        SomewhatLongRunningOperation();
        return "Success!";
    }
    catch (Exception e)
    {
        return "Error: " + e.Message;
    }
});
Task UITask = task.ContinueWith((ret) =>
{
    label.Text = ret.Result;
}, TaskScheduler.FromCurrentSynchronizationContext());

This works in .NET 3.5 and later.

How can I make a program wait for a variable change in javascript?

Alternatively, you can make a function that executes tasks based on the value of its "Static" variables, example below:

enter image description here

<!DOCTYPE html>

<div id="Time_Box"> Time </div>

<button type="button" onclick='Update_Time("on")'>Update Time On</button>
<button type="button" onclick='Update_Time("off")'>Update Time Off</button>

<script>

var Update_Time = (function () {     //_____________________________________________________________

var Static = [];             //"var" declares "Static" variable as static object in this function

    return function (Option) {

    var Local = [];           //"var" declares "Local" variable as local object in this function

        if (typeof Option === 'string'){Static.Update = Option};

        if (Static.Update === "on"){
        document.getElementById("Time_Box").innerText = Date();

        setTimeout(function(){Update_Time()}, 1000);    //update every 1 seconds
        };

    };

})();  

Update_Time('on');    //turns on time update

</script>

JavaScript: Difference between .forEach() and .map()

  • Array.forEach “executes a provided function once per array element.”

  • Array.map “creates a new array with the results of calling a provided function on every element in this array.”

So, forEach doesn’t actually return anything. It just calls the function for each array element and then it’s done. So whatever you return within that called function is simply discarded.

On the other hand, map will similarly call the function for each array element but instead of discarding its return value, it will capture it and build a new array of those return values.

This also means that you could use map wherever you are using forEach but you still shouldn’t do that so you don’t collect the return values without any purpose. It’s just more efficient to not collect them if you don’t need them.

how to install apk application from my pc to my mobile android

1.question answer-In your mobile having Developer Option in settings and enable that one. after In android studio project source file in bin--> apk file .just copy the apk file and paste in mobile memory in ur pc.. after all finished .you click that apk file in your mobile is automatically installed.

2.question answer-Your mobile is Samsung are just add Samsung Kies software in your pc..its helps to android code run in your mobile ...

JS map return object

You're very close already, you just need to return the new object that you want. In this case, the same one except with the launches value incremented by 10:

_x000D_
_x000D_
var rockets = [_x000D_
    { country:'Russia', launches:32 },_x000D_
    { country:'US', launches:23 },_x000D_
    { country:'China', launches:16 },_x000D_
    { country:'Europe(ESA)', launches:7 },_x000D_
    { country:'India', launches:4 },_x000D_
    { country:'Japan', launches:3 }_x000D_
];_x000D_
_x000D_
var launchOptimistic = rockets.map(function(elem) {_x000D_
  return {_x000D_
    country: elem.country,_x000D_
    launches: elem.launches+10,_x000D_
  } _x000D_
});_x000D_
_x000D_
console.log(launchOptimistic);
_x000D_
_x000D_
_x000D_

angularjs getting previous route path

This is how I currently store a reference to the previous path in the $rootScope:

run(['$rootScope', function($rootScope) {
        $rootScope.$on('$locationChangeStart', function() {
            $rootScope.previousPage = location.pathname;
        });
}]);

cannot import name patterns

This is the code which worked for me. My django version is 1.10.4 final

from django.conf.urls import url, include

from django.contrib import admin
admin.autodiscover()

urlpatterns = [
    # Examples:
    # url(r'^$', 'blog.views.home', name='home'),
    # url(r'^blog/', include('blog.urls')),

    url(r'^admin/', include(admin.site.urls)),
]

Set Canvas size using javascript

Try this:

var w = window,
d = document,
e = d.documentElement,
g = d.getElementsByTagName('body')[0],
xS = w.innerWidth || e.clientWidth || g.clientWidth,
yS = w.innerHeight|| e.clientHeight|| g.clientHeight;
alert(xS + ' × ' + yS);

document.write('')

works for iframe and well.

Get selected element's outer HTML

If the scenario is appending a new row dynamically, you can use this:

var row = $(".myRow").last().clone();
$(".myRow").last().after(row);

.myrow is the classname of the <tr>. It makes a copy of the last row and inserts that as a new last row. This also works in IE7, while the [0].outerHTML method does not allow assignments in ie7

Align div with fixed position on the right side

Trying to do the same thing. If you want it to be aligned on the right side then set the value of right to 0. In case you need some padding from the right, set the value to the size of the padding you need.

Example:

.test {
  position: fixed;
  right: 20px; /* Padding from the right side */
}

Cmake doesn't find Boost

Are you sure you are doing it the correct way? The idea is that CMake sets BOOST_INCLUDE_DIR, BOOST_LIBRARYDIR and BOOST_ROOT automatically. Do something like this in CMakeLists.txt:

FIND_PACKAGE(Boost)
IF (Boost_FOUND)
    INCLUDE_DIRECTORIES(${Boost_INCLUDE_DIR})
    ADD_DEFINITIONS( "-DHAS_BOOST" )
ENDIF()

If boost is not installed in a default location and can, thus, not be found by CMake, you can tell CMake where to look for boost like this:

SET(CMAKE_INCLUDE_PATH ${CMAKE_INCLUDE_PATH} "C:/win32libs/boost")
SET(CMAKE_LIBRARY_PATH ${CMAKE_LIBRARY_PATH} "C:/win32libs/boost/lib")

Of course, those two lines have to be before the FIND_PACKAGE(Boost) in CMakeLists.txt.

Round double in two decimal places in C#?

Use Math.Round

value = Math.Round(48.485, 2);

How to find out if an installed Eclipse is 32 or 64 bit version?

Open eclipse.ini in the installation directory, and observe the line with text:

plugins/org.eclipse.equinox.launcher.win32.win32.x86_64_1.0.200.v20090519 then it is 64 bit.

If it would be plugins/org.eclipse.equinox.launcher.win32.win32.x86_32_1.0.200.v20090519 then it is 32 bit.

Parsing JSON string in Java

Here is the example of one Object, For your case you have to use JSONArray.

public static final String JSON_STRING="{\"employee\":{\"name\":\"Sachin\",\"salary\":56000}}";  
try{  
   JSONObject emp=(new JSONObject(JSON_STRING)).getJSONObject("employee");  
   String empname=emp.getString("name");  
   int empsalary=emp.getInt("salary");  

   String str="Employee Name:"+empname+"\n"+"Employee Salary:"+empsalary;  
   textView1.setText(str);  

}catch (Exception e) {e.printStackTrace();}  
   //Do when JSON has problem.
}

I don't have time but tried to give an idea. If you still can't do it, then I will help.

Remove the last character from a string

An alternative to substr is the following, as a function:

substr_replace($string, "", -1)

Is it the fastest? I don't know, but I'm willing to bet these alternatives are all so fast that it just doesn't matter.

Connect to SQL Server Database from PowerShell

# database Intraction

$SQLServer = "YourServerName" #use Server\Instance for named SQL instances!
$SQLDBName = "YourDBName"
$SqlConnection = New-Object System.Data.SqlClient.SqlConnection
$SqlConnection.ConnectionString = "Server = $SQLServer; Database = $SQLDBName; 
User ID= YourUserID; Password= YourPassword" 
$SqlCmd = New-Object System.Data.SqlClient.SqlCommand
$SqlCmd.CommandText = 'StoredProcName'
$SqlCmd.Connection = $SqlConnection 
$SqlAdapter = New-Object System.Data.SqlClient.SqlDataAdapter
$SqlAdapter.SelectCommand = $SqlCmd 
$DataSet = New-Object System.Data.DataSet
$SqlAdapter.Fill($DataSet) 
$SqlConnection.Close() 

#End :database Intraction
clear

Show a number to two decimal places

Here I get two decimals after the . (dot) using a function...

function truncate_number($number, $precision = 2) {

    // Zero causes issues, and no need to truncate
    if (0 == (int)$number) {
        return $number;
    }

    // Are we negative?
    $negative = $number / abs($number);

    // Cast the number to a positive to solve rounding
    $number = abs($number);

    // Calculate precision number for dividing / multiplying
    $precision = pow(10, $precision);

    // Run the math, re-applying the negative value to ensure
    // returns correctly negative / positive
    return floor( $number * $precision ) / $precision * $negative;
}

Results from the above function:

echo truncate_number(2.56789, 1); // 2.5
echo truncate_number(2.56789);    // 2.56
echo truncate_number(2.56789, 3); // 2.567

echo truncate_number(-2.56789, 1); // -2.5
echo truncate_number(-2.56789);    // -2.56
echo truncate_number(-2.56789, 3); // -2.567

New Correct Answer

Use the PHP native function bcdiv

echo bcdiv(2.56789, 1, 1);  // 2.5
echo bcdiv(2.56789, 1, 2);  // 2.56
echo bcdiv(2.56789, 1, 3);  // 2.567
echo bcdiv(-2.56789, 1, 1); // -2.5
echo bcdiv(-2.56789, 1, 2); // -2.56
echo bcdiv(-2.56789, 1, 3); // -2.567

Javascript code for showing yesterday's date and todays date

Get yesterday date in javascript

You have to run code and check it output

_x000D_
_x000D_
    var today = new Date();_x000D_
    var yesterday = new Date(today);_x000D_
    _x000D_
    yesterday.setDate(today.getDate() - 1);_x000D_
    console.log("Original Date : ",yesterday);_x000D_
_x000D_
    const monthNames = [_x000D_
  "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"_x000D_
];_x000D_
    var month = today.getMonth() + 1_x000D_
    yesterday = yesterday.getDate() + ' ' + monthNames[month] + ' ' + yesterday.getFullYear()_x000D_
   _x000D_
    console.log("Modify Date : ",yesterday);
_x000D_
_x000D_
_x000D_

How can I download a file from a URL and save it in Rails?

I think this is the clearest way:

require 'open-uri'

File.write 'image.png', open('http://example.com/image.png').read

How do I flush the PRINT buffer in TSQL?

Building on the answer by @JoelCoehoorn, my approach is to leave all my PRINT statements in place, and simply follow them with the RAISERROR statement to cause the flush.

For example:

PRINT 'MyVariableName: ' + @MyVariableName
RAISERROR(N'', 0, 1) WITH NOWAIT

The advantage of this approach is that the PRINT statements can concatenate strings, whereas the RAISERROR cannot. (So either way you have the same number of lines of code, as you'd have to declare and set a variable to use in RAISERROR).

If, like me, you use AutoHotKey or SSMSBoost or an equivalent tool, you can easily set up a shortcut such as "]flush" to enter the RAISERROR line for you. This saves you time if it is the same line of code every time, i.e. does not need to be customised to hold specific text or a variable.

In Django, how do I check if a user is in a certain group?

Just in case if you wanna check user's group belongs to a predefined group list:

def is_allowed(user):
    allowed_group = set(['admin', 'lead', 'manager'])
    usr = User.objects.get(username=user)
    groups = [ x.name for x in usr.groups.all()]
    if allowed_group.intersection(set(groups)):
       return True
    return False

Problems with installation of Google App Engine SDK for php in OS X

It's likely that the download was corrupted if you are getting an error with the disk image. Go back to the downloads page at https://developers.google.com/appengine/downloads and look at the SHA1 checksum. Then, go to your Terminal app on your mac and run the following:

openssl sha1 [put the full path to the file here without brackets] 

For example:

openssl sha1 /Users/me/Desktop/myFile.dmg 

If you get a different value than the one on the Downloads page, you know your file is not properly downloaded and you should try again.

Add a reference column migration in Rails 4

if you like another alternate approach with up and down method try this:

  def up
    change_table :uploads do |t|
      t.references :user, index: true
    end
  end

  def down
    change_table :uploads do |t|
      t.remove_references :user, index: true
    end
  end

How to interpolate variables in strings in JavaScript, without concatenation?

Peace quote of 2020:

Console.WriteLine("I {0} JavaScript!", ">:D<");

console.log(`I ${'>:D<'} C#`)

Python: convert string from UTF-8 to Latin-1

If the previous answers do not solve your problem, check the source of the data that won't print/convert properly.

In my case, I was using json.load on data incorrectly read from file by not using the encoding="utf-8". Trying to de-/encode the resulting string to latin-1 just does not help...

dropdownlist set selected value in MVC3 Razor

To have the IT department selected, when the departments are loaded from tblDepartment table, use the following overloaded constructor of SelectList class. Notice that we are passing a value of 1 for selectedValue parameter.

ViewBag.Departments = new SelectList(db.Departments, "Id", "Name", "1");

Calculate difference between 2 date / times in Oracle SQL

If you want something that looks a bit simpler, try this for finding events in a table which occurred in the past 1 minute:

With this entry you can fiddle with the decimal values till you get the minute value that you want. The value .0007 happens to be 1 minute as far as the sysdate significant digits are concerned. You can use multiples of that to get any other value that you want:

select (sysdate - (sysdate - .0007)) * 1440 from dual;

Result is 1 (minute)

Then it is a simple matter to check for

select * from my_table where (sysdate - transdate) < .00071;

Inheritance and Overriding __init__ in python

The book is a bit dated with respect to subclass-superclass calling. It's also a little dated with respect to subclassing built-in classes.

It looks like this nowadays:

class FileInfo(dict):
    """store file metadata"""
    def __init__(self, filename=None):
        super(FileInfo, self).__init__()
        self["name"] = filename

Note the following:

  1. We can directly subclass built-in classes, like dict, list, tuple, etc.

  2. The super function handles tracking down this class's superclasses and calling functions in them appropriately.

Hashmap does not work with int, char

Generic Collection classes cant be used with primitives. Use the Character and Integer wrapper classes instead.

Map<Character , Integer > checkSum = new HashMap<Character, Integer>();

cpp / c++ get pointer value or depointerize pointer

To get the value of a pointer, just de-reference the pointer.

int *ptr;
int value;
*ptr = 9;

value = *ptr;

value is now 9.

I suggest you read more about pointers, this is their base functionality.

Python: Number of rows affected by cursor.execute("SELECT ...)

when using count(*) the result is {'count(*)': 9}

-- where 9 represents the number of rows in the table, for the instance.

So, in order to fetch the just the number, this worked in my case, using mysql 8.

cursor.fetchone()['count(*)']

How do I test for an empty JavaScript object?

Perfect and failsafe solution

I think the first accepted solution works in most cases but is not Failsafe.

The better and failsafe solution will be.

function isEmptyObject() { 
  return toString.call(obj) === "[object Object]" 
  && Object.keys(obj).length === 0;
}

or in ES6/7

const isEmptyObject = () => toString.call(obj) === "[object Object]" 
  && Object.keys(obj).length === 0;

With this approach if the obj is set to undefined or null, the code does not break. and return null.

Fetch: reject promise and catch the error if status is not OK?

Fetch promises only reject with a TypeError when a network error occurs. Since 4xx and 5xx responses aren't network errors, there's nothing to catch. You'll need to throw an error yourself to use Promise#catch.

A fetch Response conveniently supplies an ok , which tells you whether the request succeeded. Something like this should do the trick:

fetch(url).then((response) => {
  if (response.ok) {
    return response.json();
  } else {
    throw new Error('Something went wrong');
  }
})
.then((responseJson) => {
  // Do something with the response
})
.catch((error) => {
  console.log(error)
});

How to call Makefile from another Makefile?

Instead of the -f of make you might want to use the -C <path> option. This first changes the to the path '<path>', and then calles make there.

Example:

clean:
  rm -f ./*~ ./gmon.out ./core $(SRC_DIR)/*~ $(OBJ_DIR)/*.o
  rm -f ../svn-commit.tmp~
  rm -f $(BIN_DIR)/$(PROJECT)
  $(MAKE) -C gtest-1.4.0/make clean

Using different Web.config in development and production environment

In Visual Studio 2010 and above, you now have the ability to apply a transformation to your web.config depending on the build configuration.

When creating a web.config, you can expand the file in the solution explorer, and you will see two files:

  • Web.Debug.Config
  • Web.Release.Config

They contain transformation code that can be used to

  • Change the connection string
  • Remove debugging trace and settings
  • Register error pages

See Web.config Transformation Syntax for Web Application Project Deployment on MSDN for more information.

It is also possible, albeit officially unsupported, to apply the same kind of transformation to an non web application app.config file. See Phil Bolduc blog concerning how to modify your project file to add a new task to msbuild.

This is a long withstanding request on the Visual Studio Uservoice.

An extension for Visual Studio 2010 and above, "SlowCheetah," is available to take care of creating transform for any config file. Starting with Visual Studio 2017.3, SlowCheetah has been integrated into the IDE and the code base is being managed by Microsoft. This new version also support JSON transformation.

Getting the names of all files in a directory with PHP

On some OS you get . .. and .DS_Store, Well we can't use them so let's us hide them.

First start get all information about the files, using scandir()

// Folder where you want to get all files names from
$dir = "uploads/";

/* Hide this */
$hideName = array('.','..','.DS_Store');    

// Sort in ascending order - this is default
$files = scandir($dir);
/* While this to there no more files are */
foreach($files as $filename) {
    if(!in_array($filename, $hideName)){
       /* echo the name of the files */
       echo "$filename<br>";
    }
}

I can pass a variable from a JSP scriptlet to JSTL but not from JSTL to a JSP scriptlet without an error

@skaffman nailed it down. They live each in its own context. However, I wouldn't consider using scriptlets as the solution. You'd like to avoid them. If all you want is to concatenate strings in EL and you discovered that the + operator fails for strings in EL (which is correct), then just do:

<c:out value="abc${test}" />

Or if abc is to obtained from another scoped variable named ${resp}, then do:

<c:out value="${resp}${test}" />

Twitter Bootstrap - borders

If you look at Twitter's own container-app.html demo on GitHub, you'll get some ideas on using borders with their grid.

For example, here's the extracted part of the building blocks to their 940-pixel wide 16-column grid system:

.row {
    zoom: 1;
    margin-left: -20px;
}

.row > [class*="span"] {
    display: inline;
    float: left;
    margin-left: 20px;
}

.span4 {
    width: 220px;
}

To allow for borders on specific elements, they added embedded CSS to the page that reduces matching classes by enough amount to account for the border(s).

Screenshot of Example Page

For example, to allow for the left border on the sidebar, they added this CSS in the <head> after the the main <link href="../bootstrap.css" rel="stylesheet">.

.content .span4 {
    margin-left: 0;
    padding-left: 19px;
    border-left: 1px solid #eee;
}

You'll see they've reduced padding-left by 1px to allow for the addition of the new left border. Since this rule appears later in the source order, it overrides any previous or external declarations.

I'd argue this isn't exactly the most robust or elegant approach, but it illustrates the most basic example.

What's the syntax for mod in java

Also, mod can be used like this:

int a = 7;
b = a % 2;

b would equal 1. Because 7 % 2 = 1.

How can I inspect element in an Android browser?

You can inspect elements of a website in your Android device using Chrome browser.

Open your Chrome browser and go to the website you want to inspect.

Go to the address bar and type "view-source:" before the "HTTP" and reload the page.

The whole elements of the page will be shown.

How to set time to midnight for current day?

Related, so I thought I would post for others. If you want to find the UTC of the start of today (for your timezone) the following code works for any UTC offset (-23.5 thru +23.5). This looks like we add X hours then subtract X hours, but the important thing is the ".Date" after the add.

double utcOffset= 10.0;  // Set to your UTC offset in hours (eg. Melbourne Australia)
var now = DateTime.UtcNow;

var startOfToday = now.AddHours(utcOffset - 24.0).Date;
startOfToday = startOfToday.AddHours(24.0 - utcOffset);

Converting HTML string into DOM elements?

You can use a DOMParser, like so:

_x000D_
_x000D_
var xmlString = "<div id='foo'><a href='#'>Link</a><span></span></div>";_x000D_
var doc = new DOMParser().parseFromString(xmlString, "text/xml");_x000D_
console.log(doc.firstChild.innerHTML); // => <a href="#">Link..._x000D_
console.log(doc.firstChild.firstChild.innerHTML); // => Link
_x000D_
_x000D_
_x000D_

Is there a way to create interfaces in ES6 / Node 4?

Flow allows interface specification, without having to convert your whole code base to TypeScript.

Interfaces are a way of breaking dependencies, while stepping cautiously within existing code.

PostgreSQL Error: Relation already exists

In my case, I had a sequence with the same name.

Beginner Python Practice?

The Python Challenge will not only let you exercise the Python you do know, it will also require you to learn about various popular third-party packages in order to solve some of the challenges.

keypress, ctrl+c (or some combo like that)

There is a plugin for Jquery called "Hotkeys" which allows you to bind to key down combinations.

Does this do what you are after?

Jquery HotKeys - Google Code

Unable to install Maven on Windows: "JAVA_HOME is set to an invalid directory"

After lot of failed tried attempts ,I found the solution

It was the ";" at end of JAVA_HOME which I always put at end of each new variable I set. So get rid of the ;.

JAVA_HOME set it in User Variable also (without the ";" ofcourse)

how can I enable scrollbars on the WPF Datagrid?

WPF4

<DataGrid AutoGenerateColumns="True" Grid.Column="0" Grid.Row="0"
      ScrollViewer.CanContentScroll="True" 
      ScrollViewer.VerticalScrollBarVisibility="Auto"
      ScrollViewer.HorizontalScrollBarVisibility="Auto">
</DataGrid>

with : <ColumnDefinition Width="350" /> & <RowDefinition Height="300" /> works fine.

Scrollbars don't show with <ColumnDefinition Width="Auto" /> & <RowDefinition Height="300" />.

Also works fine with: <ColumnDefinition Width="*" /> & <RowDefinition Height="300" /> in the case where this is nested within an outer <Grid>.

How to allow only a number (digits and decimal point) to be typed in an input?

Please check out my component that will help you to allow only a particular data type. Currently supporting integer, decimal, string and time(HH:MM).

  • string - String is allowed with optional max length
  • integer - Integer only allowed with optional max value
  • decimal - Decimal only allowed with optional decimal points and max value (by default 2 decimal points)
  • time - 24 hr Time format(HH:MM) only allowed

https://github.com/ksnimmy/txDataType

Hope that helps.

Determine if an element has a CSS class with jQuery

In the interests of helping anyone who lands here but was actually looking for a jQuery free way of doing this:

element.classList.contains('your-class-name')

Convert text into number in MySQL query

cast(REGEXP_REPLACE(NameNumber, '[^0-9]', '') as UNSIGNED)

Convert RGBA PNG to RGB with PIL

The transparent parts mostly have RGBA value (0,0,0,0). Since the JPG has no transparency, the jpeg value is set to (0,0,0), which is black.

Around the circular icon, there are pixels with nonzero RGB values where A = 0. So they look transparent in the PNG, but funny-colored in the JPG.

You can set all pixels where A == 0 to have R = G = B = 255 using numpy like this:

import Image
import numpy as np

FNAME = 'logo.png'
img = Image.open(FNAME).convert('RGBA')
x = np.array(img)
r, g, b, a = np.rollaxis(x, axis = -1)
r[a == 0] = 255
g[a == 0] = 255
b[a == 0] = 255
x = np.dstack([r, g, b, a])
img = Image.fromarray(x, 'RGBA')
img.save('/tmp/out.jpg')

enter image description here


Note that the logo also has some semi-transparent pixels used to smooth the edges around the words and icon. Saving to jpeg ignores the semi-transparency, making the resultant jpeg look quite jagged.

A better quality result could be made using imagemagick's convert command:

convert logo.png -background white -flatten /tmp/out.jpg

enter image description here


To make a nicer quality blend using numpy, you could use alpha compositing:

import Image
import numpy as np

def alpha_composite(src, dst):
    '''
    Return the alpha composite of src and dst.

    Parameters:
    src -- PIL RGBA Image object
    dst -- PIL RGBA Image object

    The algorithm comes from http://en.wikipedia.org/wiki/Alpha_compositing
    '''
    # http://stackoverflow.com/a/3375291/190597
    # http://stackoverflow.com/a/9166671/190597
    src = np.asarray(src)
    dst = np.asarray(dst)
    out = np.empty(src.shape, dtype = 'float')
    alpha = np.index_exp[:, :, 3:]
    rgb = np.index_exp[:, :, :3]
    src_a = src[alpha]/255.0
    dst_a = dst[alpha]/255.0
    out[alpha] = src_a+dst_a*(1-src_a)
    old_setting = np.seterr(invalid = 'ignore')
    out[rgb] = (src[rgb]*src_a + dst[rgb]*dst_a*(1-src_a))/out[alpha]
    np.seterr(**old_setting)    
    out[alpha] *= 255
    np.clip(out,0,255)
    # astype('uint8') maps np.nan (and np.inf) to 0
    out = out.astype('uint8')
    out = Image.fromarray(out, 'RGBA')
    return out            

FNAME = 'logo.png'
img = Image.open(FNAME).convert('RGBA')
white = Image.new('RGBA', size = img.size, color = (255, 255, 255, 255))
img = alpha_composite(img, white)
img.save('/tmp/out.jpg')

enter image description here

jQuery: how to scroll to certain anchor/div on page load?

just use scrollTo plugin

$("document").ready(function(){
  $(window).scrollTo("#div")
})

Pass Javascript Array -> PHP

AJAX requests are no different from GET and POST requests initiated through a <form> element. Which means you can use $_GET and $_POST to retrieve the data.

When you're making an AJAX request (jQuery example):

// JavaScript file

elements = [1, 2, 9, 15].join(',')
$.post('/test.php', {elements: elements})

It's (almost) equivalent to posting this form:

<form action="/test.php" method="post">
  <input type="text" name="elements" value="1,2,9,15">
</form>

In both cases, on the server side you can read the data from the $_POST variable:

// test.php file

$elements = $_POST['elements'];
$elements = explode(',', $elements);

For the sake of simplicity I'm joining the elements with comma here. JSON serialization is a more universal solution, though.