Programs & Examples On #Memory alignment

Memory alignment means that objects and variables reside at particular offsets in the system's memory.

Python 2,3 Convert Integer to "bytes" Cleanly

I have found the only reliable, portable method to be


Just bytes([n]) does not work in python 2. Taking the scenic route through bytearray seems like the only reasonable solution.

How to import a jar in Eclipse

Here are the steps:

  1. click File > Import. The Import window opens.

  2. Under Select an import source, click J2EE > App Client JAR file.

  3. Click Next.

  4. In the Application Client file field, enter the location and name of the application client JAR file that you want to import. You can click the Browse button to select the JAR file from the file system.

  5. In the Application Client project field, type a new project name or select an application client project from the drop-down list. If you type a new name in this field, the application client project will be created based on the version of the application client JAR file, and it will use the default location.

  6. In the Target runtime drop-down list, select the application server that you want to target for your development. This selection affects the run time settings by modifying the class path entries for the project.

  7. If you want to add the new module to an enterprise application project, select the Add project to an EAR check box and then select an existing enterprise application project from the list or create a new one by clicking New.

    Note: If you type a new enterprise application project name, the enterprise application project will be created in the default location with the lowest compatible J2EE version based on the version of the project being created. If you want to specify a different version or a different location for the enterprise application, you must use the New Enterprise Application Project wizard.

  8. Click Finish to import the application client JAR file.

Is there a way to override class variables in Java?

It's called Hiding Fields

From the link above

Within a class, a field that has the same name as a field in the superclass hides the superclass's field, even if their types are different. Within the subclass, the field in the superclass cannot be referenced by its simple name. Instead, the field must be accessed through super, which is covered in the next section. Generally speaking, we don't recommend hiding fields as it makes code difficult to read.

Cannot install packages inside docker Ubuntu image

You need to update the package list in your Ubuntu:

$ sudo apt-get update
$ sudo apt-get install <package_name>

How to manage Angular2 "expression has changed after it was checked" exception when a component property depends on current datetime

In our case we FIXED by adding changeDetection into the component and call detectChanges() in ngAfterContentChecked, code as follows

  selector: 'app-spinner',
  templateUrl: './spinner.component.html',
  styleUrls: ['./spinner.component.scss'],
  changeDetection: ChangeDetectionStrategy.OnPush
export class SpinnerComponent implements OnInit, OnDestroy, AfterContentChecked {

  show = false;

  private subscription: Subscription;

  constructor(private spinnerService: SpinnerService, private changeDedectionRef: ChangeDetectorRef) { }

  ngOnInit() {
    this.subscription = this.spinnerService.spinnerState
      .subscribe((state: SpinnerState) => { =;

  ngAfterContentChecked(): void {

  ngOnDestroy() {


Writing to a file in a for loop

The main problem was that you were opening/closing files repeatedly inside your loop.

Try this approach:

with open('new.txt') as text_file, open('xyz.txt', 'w') as myfile:  
    for line in text_file:
        var1, var2 = line.split(",");

We open both files at once and because we are using with they will be automatically closed when we are done (or an exception occurs). Previously your output file was repeatedly openend inside your loop.

We are also processing the file line-by-line, rather than reading all of it into memory at once (which can be a problem when you deal with really big files).

Note that write() doesn't append a newline ('\n') so you'll have to do that yourself if you need it (I replaced your writelines() with write() as you are writing a single item, not a list of items).

When opening a file for rread, the 'r' is optional since it's the default mode.

Updating MySQL primary key

You can use the IGNORE keyword too, example:

 update IGNORE table set primary_field = 'value'...............

PostgreSQL 'NOT IN' and subquery

You could also use a LEFT JOIN and IS NULL condition:

    LEFT JOIN consols ON logs.mac = consols.mac
  consols.mac IS NULL;

An index on the "mac" columns might improve performance.

How do I encode and decode a base64 string?

I'm sharing my implementation with some neat features:

  • uses Extension Methods for Encoding class. Rationale is that someone may need to support different types of encodings (not only UTF8).
  • Another improvement is failing gracefully with null result for null entry - it's very useful in real life scenarios and supports equivalence for X=decode(encode(X)).

Remark: Remember that to use Extension Method you have to (!) import the namespace with using keyword (in this case using MyApplication.Helpers.Encoding).


namespace MyApplication.Helpers.Encoding
    public static class EncodingForBase64
        public static string EncodeBase64(this System.Text.Encoding encoding, string text)
            if (text == null)
                return null;

            byte[] textAsBytes = encoding.GetBytes(text);
            return System.Convert.ToBase64String(textAsBytes);

        public static string DecodeBase64(this System.Text.Encoding encoding, string encodedText)
            if (encodedText == null)
                return null;

            byte[] textAsBytes = System.Convert.FromBase64String(encodedText);
            return encoding.GetString(textAsBytes);

Usage example:

using MyApplication.Helpers.Encoding; // !!!

namespace ConsoleApplication1
    class Program
        static void Main(string[] args)

        static void Test1()
            string textEncoded = System.Text.Encoding.UTF8.EncodeBase64("test1...");
            System.Diagnostics.Debug.Assert(textEncoded == "dGVzdDEuLi4=");

            string textDecoded = System.Text.Encoding.UTF8.DecodeBase64(textEncoded);
            System.Diagnostics.Debug.Assert(textDecoded == "test1...");

        static void Test2()
            string textEncoded = System.Text.Encoding.UTF8.EncodeBase64(null);
            System.Diagnostics.Debug.Assert(textEncoded == null);

            string textDecoded = System.Text.Encoding.UTF8.DecodeBase64(textEncoded);
            System.Diagnostics.Debug.Assert(textDecoded == null);

Can anyone confirm that phpMyAdmin AllowNoPassword works with MySQL databases?

It works; just thought this would be helpful to someone in the future.

If you are working with MAMP, as a security measure, the $cfg['Servers'][$i]['AllowNoPassword'] = true; usually will be missing in the file so if you want to use phpMyAdmin without a password for root then simply add it preferably after the $cfg['Servers'][$i]['AllowDeny']['rules'] = array(); statement.

Then Restart your server just to be sure and you will be good to go.

How to convert enum names to string in c

You don't need to rely on the preprocessor to ensure your enums and strings are in sync. To me using macros tend to make the code harder to read.

Using Enum And An Array Of Strings

enum fruit                                                                   
    APPLE = 0, 
    /* etc. */

const char * const fruit_str[] =
    [BANANA] = "banana",
    [ORANGE] = "orange",
    [GRAPE]  = "grape",
    [APPLE]  = "apple",
    /* etc. */  

Note: the strings in the fruit_str array don't have to be declared in the same order as the enum items.

How To Use It

printf("enum apple as a string: %s\n", fruit_str[APPLE]);

Adding A Compile Time Check

If you are afraid to forget one string, you can add the following check:

#define ASSERT_ENUM_TO_STR(sarray, max) \                                       
  typedef char assert_sizeof_##max[(sizeof(sarray)/sizeof(sarray[0]) == (max)) ? 1 : -1]


An error would be reported at compile time if the amount of enum items does not match the amount of strings in the array.

iPad Safari scrolling causes HTML elements to disappear and reappear with a delay

This is the complete answer to my question. I had originally marked @Colin Williams' answer as the correct answer, as it helped me get to the complete solution. A community member, @Slipp D. Thompson edited my question, after about 2.5 years of me having asked it, and told me I was abusing SO's Q & A format. He also told me to separately post this as the answer. So here's the complete answer that solved my problem:

@Colin Williams, thank you! Your answer and the article you linked out to gave me a lead to try something with CSS.

So, I was using translate3d before. It produced unwanted results. Basically, it would chop off and NOT RENDER elements that were offscreen, until I interacted with them. So, basically, in landscape orientation, half of my site that was offscreen was not being shown. This is a iPad web app, owing to which I was in a fix.

Applying translate3d to relatively positioned elements solved the problem for those elements, but other elements stopped rendering, once offscreen. The elements that I couldn't interact with (artwork) would never render again, unless I reloaded the page.

The complete solution:

*:not(html) {
    -webkit-transform: translate3d(0, 0, 0);

Now, although this might not be the most "efficient" solution, it was the only one that works. Mobile Safari does not render the elements that are offscreen, or sometimes renders erratically, when using -webkit-overflow-scrolling: touch. Unless a translate3d is applied to all other elements that might go offscreen owing to that scroll, those elements will be chopped off after scrolling.

So, thanks again, and hope this helps some other lost soul. This surely helped me big time!

How to change a particular element of a C++ STL vector

at and operator[] both return a reference to the indexed element, so you can simply use: = -1;


l[4] = -1;

reading a line from ifstream into a string variable

Use the std::getline() from <string>.

 istream & getline(istream & is,std::string& str)

So, for your case it would be:


Anonymous method in Invoke call

I like to use Action in place of MethodInvoker, it is shorter and looks cleaner.

Invoke((Action)(() => {

// OR

Invoke((Action)delegate {


// Thread-safe update on a form control
public void DisplayResult(string text){
    if (txtResult.InvokeRequired){
        txtResult.Invoke((Action)delegate {

    txtResult.Text += text + "\r\n";

Is there a way to add/remove several classes in one single instruction with classList?

Since the add() method from the classList just allows to pass separate arguments and not a single array, you need to invoque add() using apply. For the first argument you will need to pass the classList reference from the same DOM node and as a second argument the array of classes that you want to add:

  ['class-0', 'class-1', 'class-2']

Pretty-print a Map in Java

You should be able to do what you want by doing:

System.out.println(map) for example

As long as ALL your objects in the map have overiden the toString method you would see:
{key1=value1, key2=value2} in a meaningfull manner

If this is for your code, then overiding toString is a good habit and I suggest you go for that instead.

For your example where your objects are Strings you should be fine without anything else.
I.e. System.out.println(map) would print exactly what you need without any extra code

jquery ajax function not working

you need to prevent the default behavior of your form when submitting

by adding this:

$("#postcontent").on('submit' , function(e) {


  //then the rest of your code

How to wait for 2 seconds?

How about this?

WAITFOR DELAY '00:00:02';

If you have "00:02" it's interpreting that as Hours:Minutes.

Specify sudo password for Ansible

Using ansible and the following shall work:



And just run the playbook with this inventory as:

ansible-playbook -i inventory copyTest.yml

How to delete/truncate tables from Hadoop-Hive?

You can use drop command to delete meta data and actual data from HDFS.

And just to delete data and keep the table structure, use truncate command.

For further help regarding hive ql, check language manual of hive.

Oracle Age calculation from Date of birth and Today

select (extract(year from current_date)-extract(year from Date_of_birth)) as Age from table_name;`

age=current_year - birth_year;

extract(year/month/date from date) //oracle function for extracting values from date

Replace specific characters within strings

Summarizing 2 ways to replace strings:

group<-data.frame(group=c("12357e", "12575e", "197e18", "e18947"))

1) Use gsub

group$ <- gsub("e", "", group$group)

2) Use the stringr package

group$ <- str_replace_all(group$group, "e", "")

Both will produce the desire output:

1 12357e      12357
2 12575e      12575
3 197e18      19718
4 e18947      18947

How may I sort a list alphabetically using jQuery?


<ul id="list">


function sort(ul) {
    var ul = document.getElementById(ul)
    var liArr = ul.children
    var arr = new Array()
    for (var i = 0; i < liArr.length; i++) {
    arr.forEach(function(content, index) {
        liArr[index].textContent = content


JSFiddle Demo

Here we are push all values of li elements inside ul with specific id (which we provided as function argument) to array arr and sort it using sort() method which is sorted alphabetical by default. After array arr is sorted we are loop this array using forEach() method and just replace text content of all li elements with sorted content

What is the current directory in a batch file?

%__CD__% , %CD% , %=C:%

There's also another dynamic variable %__CD__% which points to the current directory but alike %CD% it has a backslash at the end. This can be useful if you want to append files to the current directory.

With %=C:% %=D:% you can access the last accessed directory for the corresponding drive. If the variable is not defined you haven't accessed the drive on the current cmd session.

And %__APPDIR__% expands to the executable that runs the current script a.k.a. cmd.exe directory.

Share variables between files in Node.js?

Save any variable that want to be shared as one object. Then pass it to loaded module so it could access the variable through object reference..

// main.js
var myModule = require('./module.js');
var shares = {value:123};

// Initialize module and pass the shareable object

// The value was changed from init2 on the other file
console.log(shares.value); // 789

On the other file..

// module.js
var shared = null;

function init2(){
    console.log(shared.value); // 123
    shared.value = 789;

module.exports = {
        // Save the shared object on current module
        shared = obj;

        // Call something outside

How to split a dataframe string column into two columns?

TL;DR version:

For the simple case of:

  • I have a text column with a delimiter and I want two columns

The simplest solution is:

df[['A', 'B']] = df['AB'].str.split(' ', 1, expand=True)

You must use expand=True if your strings have a non-uniform number of splits and you want None to replace the missing values.

Notice how, in either case, the .tolist() method is not necessary. Neither is zip().

In detail:

Andy Hayden's solution is most excellent in demonstrating the power of the str.extract() method.

But for a simple split over a known separator (like, splitting by dashes, or splitting by whitespace), the .str.split() method is enough1. It operates on a column (Series) of strings, and returns a column (Series) of lists:

>>> import pandas as pd
>>> df = pd.DataFrame({'AB': ['A1-B1', 'A2-B2']})
>>> df

0  A1-B1
1  A2-B2
>>> df['AB_split'] = df['AB'].str.split('-')
>>> df

      AB  AB_split
0  A1-B1  [A1, B1]
1  A2-B2  [A2, B2]

1: If you're unsure what the first two parameters of .str.split() do, I recommend the docs for the plain Python version of the method.

But how do you go from:

  • a column containing two-element lists


  • two columns, each containing the respective element of the lists?

Well, we need to take a closer look at the .str attribute of a column.

It's a magical object that is used to collect methods that treat each element in a column as a string, and then apply the respective method in each element as efficient as possible:

>>> upper_lower_df = pd.DataFrame({"U": ["A", "B", "C"]})
>>> upper_lower_df

0  A
1  B
2  C
>>> upper_lower_df["L"] = upper_lower_df["U"].str.lower()
>>> upper_lower_df

   U  L
0  A  a
1  B  b
2  C  c

But it also has an "indexing" interface for getting each element of a string by its index:

>>> df['AB'].str[0]

0    A
1    A
Name: AB, dtype: object

>>> df['AB'].str[1]

0    1
1    2
Name: AB, dtype: object

Of course, this indexing interface of .str doesn't really care if each element it's indexing is actually a string, as long as it can be indexed, so:

>>> df['AB'].str.split('-', 1).str[0]

0    A1
1    A2
Name: AB, dtype: object

>>> df['AB'].str.split('-', 1).str[1]

0    B1
1    B2
Name: AB, dtype: object

Then, it's a simple matter of taking advantage of the Python tuple unpacking of iterables to do

>>> df['A'], df['B'] = df['AB'].str.split('-', 1).str
>>> df

      AB  AB_split   A   B
0  A1-B1  [A1, B1]  A1  B1
1  A2-B2  [A2, B2]  A2  B2

Of course, getting a DataFrame out of splitting a column of strings is so useful that the .str.split() method can do it for you with the expand=True parameter:

>>> df['AB'].str.split('-', 1, expand=True)

    0   1
0  A1  B1
1  A2  B2

So, another way of accomplishing what we wanted is to do:

>>> df = df[['AB']]
>>> df

0  A1-B1
1  A2-B2

>>> df.join(df['AB'].str.split('-', 1, expand=True).rename(columns={0:'A', 1:'B'}))

      AB   A   B
0  A1-B1  A1  B1
1  A2-B2  A2  B2

The expand=True version, although longer, has a distinct advantage over the tuple unpacking method. Tuple unpacking doesn't deal well with splits of different lengths:

>>> df = pd.DataFrame({'AB': ['A1-B1', 'A2-B2', 'A3-B3-C3']})
>>> df
0     A1-B1
1     A2-B2
2  A3-B3-C3
>>> df['A'], df['B'], df['C'] = df['AB'].str.split('-')
Traceback (most recent call last):
ValueError: Length of values does not match length of index

But expand=True handles it nicely by placing None in the columns for which there aren't enough "splits":

>>> df.join(
...     df['AB'].str.split('-', expand=True).rename(
...         columns={0:'A', 1:'B', 2:'C'}
...     )
... )
         AB   A   B     C
0     A1-B1  A1  B1  None
1     A2-B2  A2  B2  None
2  A3-B3-C3  A3  B3    C3

Disable a link in Bootstrap

I think you need the btn class.
It would be like this:

<a class="btn disabled" href="#">Disabled link</a>

No Multiline Lambda in Python: Why not?

(For anyone still interested in the topic.)

Consider this (includes even usage of statements' return values in further statements within the "multiline" lambda, although it's ugly to the point of vomiting ;-)

>>> def foo(arg):
...     result = arg * 2;
...     print "foo(" + str(arg) + ") called: " + str(result);
...     return result;
>>> f = lambda a, b, state=[]: [
...     state.append(foo(a)),
...     state.append(foo(b)),
...     state.append(foo(state[0] + state[1])),
...     state[-1]
... ][-1];
>>> f(1, 2);
foo(1) called: 2
foo(2) called: 4
foo(6) called: 12

How to enable and use HTTP PUT and DELETE with Apache2 and PHP?

The technical limitations with using PUT and DELETE requests does not lie with PHP or Apache2; it is instead on the burden of the browser to sent those types of requests.

Simply putting <form action="" method="PUT"> will not work because there are no browsers that support that method (and they would simply default to GET, treating PUT the same as it would treat gibberish like FDSFGS). Sadly those HTTP verbs are limited to the realm of non-desktop application browsers (ie: web service consumers).

What does __FILE__ mean in Ruby?

It is a reference to the current file name. In the file foo.rb, __FILE__ would be interpreted as "foo.rb".

Edit: Ruby 1.9.2 and 1.9.3 appear to behave a little differently from what Luke Bayes said in his comment. With these files:

# test.rb
puts __FILE__
require './dir2/test.rb'
# dir2/test.rb
puts __FILE__

Running ruby test.rb will output


Rerouting stdin and stdout from C

I think you're looking for something like freopen()

What are OLTP and OLAP. What is the difference between them?

The difference is quite simple:

OLTP (Online Transaction Processing)

OLTP is a class of information systems that facilitate and manage transaction-oriented applications. OLTP has also been used to refer to processing in which the system responds immediately to user requests. Online transaction processing applications are high throughput and insert or update-intensive in database management. Some examples of OLTP systems include order entry, retail sales, and financial transaction systems.

OLAP (Online Analytical Processing)

OLAP is part of the broader category of business intelligence, which also encompasses relational database, report writing and data mining. Typical applications of OLAP include business reporting for sales, marketing, management reporting, business process management (BPM), budgeting and forecasting, financial reporting and similar areas.

See more details OLTP and OLAP

Intersect Two Lists in C#

If you have objects, not structs (or strings), then you'll have to intersect their keys first, and then select objects by those keys:

var ids = list1.Select(x => x.Id).Intersect(list2.Select(x => x.Id));
var result = list1.Where(x => ids.Contains(x.Id));

How to execute 16-bit installer on 64-bit Win7?

I am mostly posting this in case someone comes along and is not aware that VB2005 and VB2008 have update utilities that convert older VB versions to it's format. Especially since no one bothered to point that fact out.

Points taken, but maintenance of this VB6 product is unavoidable. It would also be costly in man-hours to replace the Sheridan controls with native ones. Simply developing on a 32-bit machine would be a better alternative than doing that. I would like to install everything on Win7 64-bit ideally. – CJ7

Have you tried utilizing the code upgrade functionality of VB Express 2005+?

If not, 1. Make a copy of your code - folder and all. 2. Import the project into VB express 2005. This will activate the update wizard. 3. Debug and get the app running. 4. Create a new installer utilizing MS free tool. 5. You now have a 32 bit application with a 32 bit installer.

Until you do this, you will never know how difficult or hard it will be to update and modernize the program. It is quite possible that the wizard will update the Sheridan controls to the VB 2005 controls. Again, you will not know if it does and how well it does it until you try it.

Alternatively, stick with the 32 Bit versions of Windows 7 and 8. I have Windows 7 x64 and a program that will not run. However, the program will run in Windows 7 32 bit as well as Windows 8 RC 32 bit. Under Windows 8 RC 32, I was prompted to enable 16 bit emulation which I did and the program rand quite fine afterwords.

Expected response code 220 but got code "", with message "" in Laravel

That error message means that there was not response OR the server could not be connected.

The following settings worked on my end:

'stream' => [
        'ssl' => [
            'allow_self_signed' => true,
            'verify_peer' => false,
            'verify_peer_name' => false,

Note that my SMTP settings are:

MAIL_USERNAME=[full gmail address]
MAIL_PASSWORD=[App Password obtained after two step verification]

Get week of year in JavaScript like in PHP

The code snippet which works pretty well for me is this one:

var yearStart = +new Date(d.getFullYear(), 0, 1);
var today = +new Date(d.getFullYear(),d.getMonth(),d.getDate());
var dayOfYear = ((today - yearStart + 1) / 86400000);
return Math.ceil(dayOfYear / 7).toString();

d is my Date for which I want the current week number.
The + converts the Dates into numbers (working with TypeScript).

Retrofit and GET using parameters

AFAIK, {...} can only be used as a path, not inside a query-param. Try this instead:

public interface FooService {    

    void getPositionByZip(@Query("address") String address, Callback<String> cb);

If you have an unknown amount of parameters to pass, you can use do something like this:

public interface FooService {    

    void getPositionByZip(@FieldMap Map<String, String> params, Callback<String> cb);


I ended up leaving the common properties from the SELECT queries and making a second SELECT query later on in the page. I used a php IF command to call for different scripts depending on the first SELECT query, the scripts contained the second SELECT query.

Send an Array with an HTTP Get

That depends on what the target server accepts. There is no definitive standard for this. See also a.o. Wikipedia: Query string:

While there is no definitive standard, most web frameworks allow multiple values to be associated with a single field (e.g. field1=value1&field1=value2&field2=value3).[4][5]

Generally, when the target server uses a strong typed programming language like Java (Servlet), then you can just send them as multiple parameters with the same name. The API usually offers a dedicated method to obtain multiple parameter values as an array.

String[] foo = request.getParameterValues("foo"); // [value1, value2, value3]

The request.getParameter("foo") will also work on it, but it'll return only the first value.

String foo = request.getParameter("foo"); // value1

And, when the target server uses a weak typed language like PHP or RoR, then you need to suffix the parameter name with braces [] in order to trigger the language to return an array of values instead of a single value.

$foo = $_GET["foo"]; // [value1, value2, value3]
echo is_array($foo); // true

In case you still use foo=value1&foo=value2&foo=value3, then it'll return only the first value.

$foo = $_GET["foo"]; // value1
echo is_array($foo); // false

Do note that when you send foo[]=value1&foo[]=value2&foo[]=value3 to a Java Servlet, then you can still obtain them, but you'd need to use the exact parameter name including the braces.

String[] foo = request.getParameterValues("foo[]"); // [value1, value2, value3]

Pandas index column title or name

Use df.index.rename('foo', inplace=True) to set the index name.

Seems this api is available since pandas 0.13.

HTML5 Audio stop function

This approach is "brute force", but it works assuming using jQuery is "allowed". Surround your "player" <audio></audio> tags with a div (here with an id of "plHolder").

<div id="plHolder">
     <audio controls id="player">

Then this javascript should work:

function stopAudio() {
    var savePlayer = $('#plHolder').html(); // Save player code
    $('#player').remove(); // Remove player from DOM
    $('#FlHolder').html(savePlayer); // Restore it

How can I iterate over an enum?

The typical way is as follows:

enum Foo {

for ( int fooInt = One; fooInt != Last; fooInt++ )
   Foo foo = static_cast<Foo>(fooInt);
   // ...

Please note, the enum Last is meant to be skipped by the iteration. Utilizing this "fake" Last enum, you don't have to update your terminating condition in the for loop to the last "real" enum each time you want to add a new enum. If you want to add more enums later, just add them before Last. The loop in this example will still work.

Of course, this breaks down if the enum values are specified:

enum Foo {
  One = 1,
  Two = 9,
  Three = 4,

This illustrates that an enum is not really meant to iterate through. The typical way to deal with an enum is to use it in a switch statement.

switch ( foo )
    case One:
        // ..
    case Two:  // intentional fall-through
    case Three:
        // ..
    case Four:
        // ..
        assert( ! "Invalid Foo enum value" );

If you really want to enumerate, stuff the enum values in a vector and iterate over that. This will properly deal with the specified enum values as well.

Removing NA in dplyr pipe

I don't think desc takes an na.rm argument... I'm actually surprised it doesn't throw an error when you give it one. If you just want to remove NAs, use na.omit (base) or tidyr::drop_na:

outcome.df %>%
  na.omit() %>%
  group_by(Hospital, State) %>%
  arrange(desc(HeartAttackDeath)) %>%

outcome.df %>%
  drop_na() %>%
  group_by(Hospital, State) %>%
  arrange(desc(HeartAttackDeath)) %>%

If you only want to remove NAs from the HeartAttackDeath column, filter with, or use tidyr::drop_na:

outcome.df %>%
  filter(! %>%
  group_by(Hospital, State) %>%
  arrange(desc(HeartAttackDeath)) %>%

outcome.df %>%
  drop_na(HeartAttackDeath) %>%
  group_by(Hospital, State) %>%
  arrange(desc(HeartAttackDeath)) %>%

As pointed out at the dupe, complete.cases can also be used, but it's a bit trickier to put in a chain because it takes a data frame as an argument but returns an index vector. So you could use it like this:

outcome.df %>%
  filter(complete.cases(.)) %>%
  group_by(Hospital, State) %>%
  arrange(desc(HeartAttackDeath)) %>%

remove all special characters in java

Your problem is that the indices returned by match.start() correspond to the position of the character as it appeared in the original string when you matched it; however, as you rewrite the string c every time, these indices become incorrect.

The best approach to solve this is to use replaceAll, for example:

        System.out.println(c.replaceAll("[^a-zA-Z0-9]", ""));

LINQ to Entities does not recognize the method 'System.String ToString()' method, and this method cannot be translated into a store expression

The problem is that you are calling ToString in a LINQ to Entities query. That means the parser is trying to convert the ToString call into its equivalent SQL (which isn't possible...hence the exception).

All you have to do is move the ToString call to a separate line:

var keyString = item.Key.ToString();

var pages = from p in context.entities
            where p.Serial == keyString
            select p;

How do I drop a function if it already exists?

This works for any object, not just functions:


then just add your flavor of object, as in:

   DROP FUNCTION YourFunction

What is the best way to determine a session variable is null or empty in C#?

The 'as' notation in c# 3.0 is very clean. Since all session variables are nullable objects, this lets you grab the value and put it into your own typed variable without worry of throwing an exception. Most objects can be handled this way.

string mySessionVar = Session["mySessionVar"] as string;

My concept is that you should pull your Session variables into local variables and then handle them appropriately. Always assume your Session variables could be null and never cast them into a non-nullable type.

If you need a non-nullable typed variable you can then use TryParse to get that.

int mySessionInt;
if (!int.TryParse(mySessionVar, out mySessionInt)){
   // handle the case where your session variable did not parse into the expected type 
   // e.g. mySessionInt = 0;

Angular 2 - Using 'this' inside setTimeout

You need to use Arrow function ()=> ES6 feature to preserve this context within setTimeout.

// var that = this;                             // no need of this line
this.messageSuccess = true;

setTimeout(()=>{                           //<<<---using ()=> syntax
      this.messageSuccess = false;
 }, 3000);

Constant pointer vs Pointer to constant

Please refer the following link for better understanding about the difference between Const pointer and Pointer on a constant value.

constant pointer vs pointer on a constant value

How to decrease prod bundle size?

Check you have configuration named "production" for ng build --prod, since it is shorthand for ng build --configuration=production No answer solved my problem, because the problem was sitting right in front of the screen. I think this might be quite common... I've internationalized the app with i18n renaming all configurations to e.g. production-en. Then I built with ng build --prod assuming, that the default optimization is used and should be close to optimal, but in fact just ng build has been executed resulting in 7mb bundle instead of 250kb.

Tensorflow installation error: not a supported wheel on this platform

The pip wheel contains the python version in its name (cp34-cp34m). If you download the whl file and rename it to say py3-none or instead, it should work. Can you try that?

The installation won't work for anaconda users that choose python 3 support because the installation procedure is asking to create a python 3.5 environment and the file is currently called cp34-cp34m. So renaming it would do the job for now.

sudo pip3 install --upgrade

This will produced the exact error message you got above. However, when you will downloaded the file yourself and rename it to "tensorflow-0.7.0-py3-none-linux_x86_64.whl", then execute the command again with changed filename, it should work fine.

Test if string is a number in Ruby on Rails

Relying on the raised exception is not the fastest, readable nor reliable solution.
I'd do the following :

my_string.should =~ /^[0-9]+$/

List all sequences in a Postgres db 8.1 with SQL

after a little bit of pain, i got it.

the best way to achieve this is to list all tables

select * from pg_tables where schemaname = '<schema_name>'

and then, for each table, list all columns with attributes

select * from information_schema.columns where table_name = '<table_name>'

then, for each column, test if it has a sequence

select pg_get_serial_sequence('<table_name>', '<column_name>')

and then, get the information about this sequence

select * from <sequence_name>

How to remove the first Item from a list?

You can find a short collection of useful list functions here.


>>> l = ['a', 'b', 'c', 'd']
>>> l.pop(0)
>>> l
['b', 'c', 'd']

del list[index]

>>> l = ['a', 'b', 'c', 'd']
>>> del l[0]
>>> l
['b', 'c', 'd']

These both modify your original list.

Others have suggested using slicing:

  • Copies the list
  • Can return a subset

Also, if you are performing many pop(0), you should look at collections.deque

from collections import deque
>>> l = deque(['a', 'b', 'c', 'd'])
>>> l.popleft()
>>> l
deque(['b', 'c', 'd'])
  • Provides higher performance popping from left end of the list

How to Set OnClick attribute with value containing function in ie8?

your best bet is to use a javascript framework like jquery or prototype, but, failing that, you should use:

if (foo.addEventListener) 
    foo.addEventListener('click',doit,false); //everything else    
else if (foo.attachEvent)
    foo.attachEvent('onclick',doit);  //IE only


also, your function is a little off. it should be

var doit = function(){
    alert('hello world!');

Saving binary data as file using JavaScript from a browser

This is possible if the browser supports the download property in anchor elements.

var sampleBytes = new Int8Array(4096);

var saveByteArray = (function () {
    var a = document.createElement("a");
    document.body.appendChild(a); = "display: none";
    return function (data, name) {
        var blob = new Blob(data, {type: "octet/stream"}),
            url = window.URL.createObjectURL(blob);
        a.href = url; = name;;

saveByteArray([sampleBytes], 'example.txt');


Interpreting "condition has length > 1" warning from `if` function

Just adding a point to the whole discussion as to why this warning comes up (It wasn't clear to me before). The reason one gets this is as mentioned before is because 'a' in this case is a vector and the inequality 'a>0' produces another vector of TRUE and FALSE (where 'a' is >0 or not).

If you would like to instead test if any value of 'a>0', you can use functions - 'any' or 'all'


Error when checking model input: expected convolution2d_input_1 to have 4 dimensions, but got array with shape (32, 32, 3)

I got the same error while working with mnist data set, looks like a problem with the dimensions of X_train. I added another dimension and it solved the purpose.

X_train, X_test, \ y_train, y_test = train_test_split(X_reshaped, y_labels, train_size = 0.8, random_state = 42)

X_train = X_train.reshape(-1,28, 28, 1)

X_test = X_test.reshape(-1,28, 28, 1)

How do I obtain crash-data from my Android application?

Late to the party, I support and believe ACRA is the best option among all. Its easy to setup and configure. I have created a detailed guide with inputs from all over to fetch the crash report using ACRA and mail the same to my email address using MandrillAp.

Link to post:

Link to sample project on github:

How can I create a Java 8 LocalDate from a long Epoch time in Milliseconds?

replace now.getTime() with your long value.

//GET UTC time for current date
        Date now= new Date();
        //LocalDateTime utcDateTimeForCurrentDateTime = Instant.ofEpochMilli(now.getTime()).atZone(ZoneId.of("UTC")).toLocalDateTime();
        LocalDate localDate = Instant.ofEpochMilli(now.getTime()).atZone(ZoneId.of("UTC")).toLocalDate();
        DateTimeFormatter dTF2 = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm");
        System.out.println(" formats as " + dTF2.format(utcDateTimeForCurrentDateTime));

How to find row number of a value in R code

Instead of 1:nrow(mydata_2) you can simply use the which() function: which(mydata_2[,4] == 1578)

Although as it was pointed out above, the 3rd column contains 1578, not the fourth: which(mydata_2[,3] == 1578)

Cast Int to enum in Java

MyEnum.values()[x] is an expensive operation. If the performance is a concern, you may want to do something like this:

public enum MyEnum {

    public static MyEnum fromInteger(int x) {
        switch(x) {
        case 0:
            return EnumValue1;
        case 1:
            return EnumValue2;
        return null;

How can I upload fresh code at github?

You can create GitHub repositories via the command line using their Repositories API (

Check Creating github repositories with command line | Do it yourself Android for example usage.

R ggplot2: stat_count() must not be used with a y aesthetic error in Bar graph

I was looking for the same and this may also work

p.Wages.all.A_MEAN <- Wages.all %>%
                  group_by(`Career Cluster`, Year)%>%
                  summarize(ANNUAL.MEAN.WAGE = mean(A_MEAN))

names(p.Wages.all.A_MEAN) [1] "Career Cluster" "Year" "ANNUAL.MEAN.WAGE"

p.Wages.all.a.mean <- ggplot(p.Wages.all.A_MEAN, aes(Year, ANNUAL.MEAN.WAGE , color= `Career Cluster`))+
                  geom_point(aes(col=`Career Cluster` ), pch=15, size=2.75, alpha=1.5/4)+
                  theme(axis.text.x = element_text(color="#993333",  size=10, angle=0)) #face="italic",

How to copy a row and insert in same table with a autoincrement field in MySQL?

Try this:

INSERT INTO test_table (SELECT null,txt FROM test_table)

Every time you run this query, This will insert all the rows again with new ids. values in your table and will increase exponentially.

I used a table with two columns i.e id and txt and id is auto increment.

In Visual Studio C++, what are the memory allocation representations?

There's actually quite a bit of useful information added to debug allocations. This table is more complete:

Address  Offset After HeapAlloc() After malloc() During free() After HeapFree() Comments
0x00320FD8  -40    0x01090009    0x01090009     0x01090009    0x0109005A     Win32 heap info
0x00320FDC  -36    0x01090009    0x00180700     0x01090009    0x00180400     Win32 heap info
0x00320FE0  -32    0xBAADF00D    0x00320798     0xDDDDDDDD    0x00320448     Ptr to next CRT heap block (allocated earlier in time)
0x00320FE4  -28    0xBAADF00D    0x00000000     0xDDDDDDDD    0x00320448     Ptr to prev CRT heap block (allocated later in time)
0x00320FE8  -24    0xBAADF00D    0x00000000     0xDDDDDDDD    0xFEEEFEEE     Filename of malloc() call
0x00320FEC  -20    0xBAADF00D    0x00000000     0xDDDDDDDD    0xFEEEFEEE     Line number of malloc() call
0x00320FF0  -16    0xBAADF00D    0x00000008     0xDDDDDDDD    0xFEEEFEEE     Number of bytes to malloc()
0x00320FF4  -12    0xBAADF00D    0x00000001     0xDDDDDDDD    0xFEEEFEEE     Type (0=Freed, 1=Normal, 2=CRT use, etc)
0x00320FF8  -8     0xBAADF00D    0x00000031     0xDDDDDDDD    0xFEEEFEEE     Request #, increases from 0
0x00320FFC  -4     0xBAADF00D    0xFDFDFDFD     0xDDDDDDDD    0xFEEEFEEE     No mans land
0x00321000  +0     0xBAADF00D    0xCDCDCDCD     0xDDDDDDDD    0xFEEEFEEE     The 8 bytes you wanted
0x00321004  +4     0xBAADF00D    0xCDCDCDCD     0xDDDDDDDD    0xFEEEFEEE     The 8 bytes you wanted
0x00321008  +8     0xBAADF00D    0xFDFDFDFD     0xDDDDDDDD    0xFEEEFEEE     No mans land
0x0032100C  +12    0xBAADF00D    0xBAADF00D     0xDDDDDDDD    0xFEEEFEEE     Win32 heap allocations are rounded up to 16 bytes
0x00321010  +16    0xABABABAB    0xABABABAB     0xABABABAB    0xFEEEFEEE     Win32 heap bookkeeping
0x00321014  +20    0xABABABAB    0xABABABAB     0xABABABAB    0xFEEEFEEE     Win32 heap bookkeeping
0x00321018  +24    0x00000010    0x00000010     0x00000010    0xFEEEFEEE     Win32 heap bookkeeping
0x0032101C  +28    0x00000000    0x00000000     0x00000000    0xFEEEFEEE     Win32 heap bookkeeping
0x00321020  +32    0x00090051    0x00090051     0x00090051    0xFEEEFEEE     Win32 heap bookkeeping
0x00321024  +36    0xFEEE0400    0xFEEE0400     0xFEEE0400    0xFEEEFEEE     Win32 heap bookkeeping
0x00321028  +40    0x00320400    0x00320400     0x00320400    0xFEEEFEEE     Win32 heap bookkeeping
0x0032102C  +44    0x00320400    0x00320400     0x00320400    0xFEEEFEEE     Win32 heap bookkeeping

Rails server says port already used, how to kill that process?

To kill process on a specific port, you can try this

npx kill-port [port-number]

Is there such a thing as min-font-size and max-font-size?

I am coming a bit late here, I don't get that much credit for it, I am just doing a mix of the answers below because I was forced to do that for a project.

So to answer the question : There is no such thing as this CSS property. I don't know why, but I think it's because they are afraid of a misused of this property, but I don't find any use case where it can be a serious problem.

Whatever, what are the solutions ?

Two tools will allow us to do that : media queries ans vw property

1) There is a "fool" solution consisting in making a media query for every step we eant in our css, changing font from a fixed amount to another fixed amount. It works, but it is very boring to do, and you don't have a smooth linear aspect.

2) As AlmostPitt explained, there is a brillant solution for the minima :

font-size: calc(7px + .5vw);

Minimum here would be 7px in addition to 0.5% of the view width. That is already really cool and working in most of cases. It does not require any media query, you just have to spend some time finding the right parameters.

As you noticed it is a linear function, basic maths learn you that two points already find you the parameters. Then just fix the font-size in px you want for very large screens and for mobile version, then calculate if you want to do a scientific method. Thought, it is absolutely not necessary and you can just go by trying.

3) Let's suppose you have a very boring client (like me) who absolutely wants a title to be one line and no more. If you used AlmostPitt solution, then you are in trouble because your font will keep growing, and if you have a fixed width container (like bootstrap stoping at 1140px or something in large windows). Here I suggest you to use also a media query. In fact you can just find the amout of px size maximum you can handle in your container before the aspect become unwanted (pxMax). This will be your maximum. Then you just have to find the exact screen width you must stop (wMax). (I let you inverse a linear function on your own).

After that just do

@media (min-width: [wMax]px) {
        font-size: [pxMax]px;

Then it is perfectly linear and your font-size stop growing ! Notice that you don't need to put your previous css property (calc...) in a media query under wMax because media query are considered as more imnportant and it will overwrite the previous property.

I don't think it is useful to make a snippet for this, as you would have trouble to make it to whole screen and it is not rocket science afterall.

Hope this could help others, and don't forget to thank AlmostPitt for his solution.

What is a "callable"?

A callable is an object allows you to use round parenthesis ( ) and eventually pass some parameters, just like functions.

Every time you define a function python creates a callable object. In example, you could define the function func in these ways (it's the same):

class a(object):
    def __call__(self, *args):
        print 'Hello'

func = a()

# or ... 
def func(*args):
    print 'Hello'

You could use this method instead of methods like doit or run, I think it's just more clear to see obj() than obj.doit()

How to parse JSON in Java

The below example shows how to read the text in the question, represented as the "jsonText" variable. This solution uses the Java EE7 javax.json API (which is mentioned in some of the other answers). The reason I've added it as a separate answer is that the following code shows how to actually access some of the values shown in the question. An implementation of the javax.json API would be required to make this code run. The full package for each of the classes required was included as I didn't want to declare "import" statements.

javax.json.JsonReader jr = 
    javax.json.Json.createReader(new StringReader(jsonText));
javax.json.JsonObject jo = jr.readObject();

//Read the page info.
javax.json.JsonObject pageInfo = jo.getJsonObject("pageInfo");

//Read the posts.
javax.json.JsonArray posts = jo.getJsonArray("posts");
//Read the first post.
javax.json.JsonObject post = posts.getJsonObject(0);
//Read the post_id field.
String postId = post.getString("post_id");

Now, before anyone goes and downvotes this answer because it doesn't use GSON, org.json, Jackson, or any of the other 3rd party frameworks available, it's an example of "required code" per the question to parse the provided text. I am well aware that adherence to the current standard JSR 353 was not being considered for JDK 9 and as such the JSR 353 spec should be treated the same as any other 3rd party JSON handling implementation.

mysql_fetch_array()/mysql_fetch_assoc()/mysql_fetch_row()/mysql_num_rows etc... expects parameter 1 to be resource

Make Sure You're Not Closing Database By using db_close() Before To Running Your Query:

If you're using multiple queries in a script even you're including other pages which contains queries or database connection, then it might be possible that at any place you use db_close() that would close your database connection so make sure you're not doing this mistake in your scripts.

How can I check if an InputStream is empty without reading from it?

No, you can't. InputStream is designed to work with remote resources, so you can't know if it's there until you actually read from it.

You may be able to use a, however, which allows you to read from the stream to see if there's something there, and then "push it back" up the stream (that's not how it really works, but that's the way it behaves to client code).

PostgreSQL: How to change PostgreSQL user password?

In general, just use pg admin UI for doing db related activity.

If instead you are focusin more in automating database setup for your local development, or CI etc...

For example, you can use a simple combo like this.

(a) Create a dummy super user via jenkins with a command similar to this:

docker exec -t postgres11-instance1 createuser --username=postgres --superuser experiment001

this will create a super user called experiment001 in you postgres db.

(b) Give this user some password by running a NON-Interactive SQL command.

docker exec -t postgres11-instance1 psql -U experiment001 -d postgres -c "ALTER USER experiment001 WITH PASSWORD 'experiment001' "

Postgres is probably the best database out there for command line (non-interactive) tooling. Creating users, running SQL, making backup of database etc... In general it is all quite basic with postgres and it is overall quite trivial to integrate this into your development setup scripts or into automated CI configuration.

Edittext change border color with shape.xml

Why using selector as the root tag? selector is used for applying multiple alternate drawables for different states of the view, so in this case, there is no need for selector.

Try the following code.

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="">

    <!-- Background Color -->
    <solid android:color="#ffffff" />

    <!-- Border Color -->
    <stroke android:width="1dp" android:color="#ff9900" />

    <!-- Round Corners -->
    <corners android:radius="5dp" />


Also It's worth mentioning that all color entries support alpha channel as well, meaning that you can have transparent or semi-transparent colors. For example #RRGGBBAA.

Bootstrap: how do I change the width of the container?

Use a wrapper selector and create a container that has a 100% width inside of that wrapper to encapsulate the entire page.

<style>#wrapper {width: 1000px;} 
#wrapper .container {max-width: 100%; display: block;}</style>
<div id="wrapper">
  <div class="container">
    <div class="row">....

Now the maximum width is set to 1000px and you need no less or sass.

How to consume REST in Java

Its just a 2 line of code.

import org.springframework.web.client.RestTemplate;

RestTemplate restTemplate = new RestTemplate();
YourBean obj = restTemplate.getForObject("", YourBean.class);

Ref. consuming-rest

How to use QTimer


    #ifndef MYTIMER_H
    #define MYTIMER_H

    #include <QTimer>

    class MyTimer : public QObject
        QTimer *timer;

    public slots:
        void MyTimerSlot();

    #endif // MYTIME


#include "mytimer.h"
#include <QDebug>

    // create a timer
    timer = new QTimer(this);

    // setup signal and slot
    connect(timer, SIGNAL(timeout()),
          this, SLOT(MyTimerSlot()));

    // msec

void MyTimer::MyTimerSlot()
    qDebug() << "Timer...";


#include <QCoreApplication>
#include "mytimer.h"

int main(int argc, char *argv[])
    QCoreApplication a(argc, argv);

    // Create MyTimer instance
    // QTimer object will be created in the MyTimer constructor
    MyTimer timer;

    return a.exec();

If we run the code:



How to check certificate name and alias in keystore files?

This will list all certificates:

keytool -list -keystore "$JAVA_HOME/jre/lib/security/cacerts"

How can I have a newline in a string in sh?

This isn't ideal, but I had written a lot of code and defined strings in a way similar to the method used in the question. The accepted solution required me to refactor a lot of the code so instead, I replaced every \n with "$'\n'" and this worked for me.

How to get difference between two rows for a column field?

   ISNULL([next].Value, 0) - [current].Value
   sourceTable       AS [current]
   sourceTable       AS [next]
      ON [next].rowInt = (SELECT MIN(rowInt) FROM sourceTable WHERE rowInt > [current].rowInt)


Thinking about it, using a subquery in the select (ala Quassnoi's answer) may be more efficient. I would trial different versions, and look at the execution plans to see which would perform best on the size of data set that you have...


I still see this garnering votes, though it's unlikely many people still use SQL Server 2005.

If you have access to Windowed Functions such as LEAD(), then use that instead...

  LEAD(Value, 1, 0) OVER (ORDER BY RowInt) - Value

Default value of 'boolean' and 'Boolean' in Java

Boolean is an Object. So if it's an instance variable it will be null. If it's declared within a method you will have to initialize it, or there will be a compiler error.

If you declare as a primitive i.e. boolean. The value will be false by default if it's an instance variable (or class variable). If it's declared within a method you will still have to initialize it to either true or false, or there will be a compiler error.

Login with facebook android sdk app crash API 4

The official answer from Facebook (


The facebook android sdk no longer supports android 1.5 and 1.6. Please upgrade to the next api version.

Good luck with your implementation.

Bootstrap Align Image with text

I think this is helpful for you

<div class="container">
        <div class="page-header">
                <h1>About Me</h1>
            </div><!--END page-header-->
        <div class="row" id="features">
                <div class="col-sm-6 feature">
                        <img src="" alt="Web Design" class="img-circle">
                </div><!--END feature-->

                <div class="col-sm-6 feature">
                        <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod
tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam,</p>
                </div><!--END feature-->
            </div><!--end features-->
    </div><!--end container-->

Getting value from table cell in JavaScript...not jQuery

Guess I'm going to answer my own questions....Sarfraz was close but not quite right. The correct answer is:


Make header and footer files to be included in multiple html pages

Must you use html file structure with JavaScript? Have you considered using PHP instead so that you can use simple PHP include object?

If you convert the file names of your .html pages to .php - then at the top of each of your .php pages you can use one line of code to include the content from your header.php

<?php include('header.php'); ?>

Do the same in the footer of each page to include the content from your footer.php file

<?php include('footer.php'); ?>

No JavaScript / Jquery or additional included files required.

NB You could also convert your .html files to .php files using the following in your .htaccess file

# re-write html to php
RewriteRule ^(.*)\.html$ $1.php [L]
RewriteRule ^(.+)/$ http://%{HTTP_HOST}/$1 [R=301,L]

# re-write no extension to .php
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^([^\.]+)$ $1.php [NC,L]

How to set enum to null

Make your variable nullable. Like:

Color? color = null;


Nullable<Color> color = null;

Mean filter for smoothing images in Matlab

and the convolution is defined through a multiplication in transform domain:

conv2(x,y) = fftshift(ifft2(fft2(x).*fft2(y)))

if one channel is considered... for more channels this has to be done every channel

How do I make a JAR from a .java file?

Perhaps the most beginner-friendly way to compile a JAR from your Java code is to use an IDE (integrated development environment; essentially just user-friendly software for development) like Netbeans or Eclipse.

  • Install and set-up an IDE. Here is the latest version of Eclipse.
  • Create a project in your IDE and put your Java files inside of the project folder.
  • Select the project in the IDE and export the project as a JAR. Double check that the appropriate java files are selected when exporting.

You can always do this all very easily with the command line. Make sure that you are in the same directory as the files targeted before executing a command such as this:

jar -cf YourJar.jar YourApp.class

...changing "YourApp" and "YourJar" to the proper names of your files, respectively.

Automatically create an Enum based on values in a database lookup table?

Using dynamic enums is bad no matter which way. You will have to go through the trouble of "duplicating" the data to ensure clear and easy code easy to maintain in the future.

If you start introducing automatic generated libraries, you are for sure causing more confusion to future developers having to upgrade your code than simply making your enum coded within the appropriate class object.

The other examples given sound nice and exciting, but think about the overhead on code maintenance versus what you get from it. Also, are those values going to change that frequently?

How to check currently internet connection is available or not in android

public boolean isOnline() {
    ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo netInfo = cm.getActiveNetworkInfo();
    if (netInfo != null && netInfo.isConnectedOrConnecting()) {
        return true;
    } else {
        return false;

Google recommends this code block for checking internet connection. Because the device may have not internet connection even if it is connected to WiFi.

Update with two tables?

I was scratching my head, not being able to get John Sansom's Join syntax work, at least in MySQL 5.5.30 InnoDB.

It turns out that this doesn't work.

    SET A.x = 1
        ON =
WHERE A.x <> B.x

But this works:

    ON =
SET A.x = 1
WHERE A.x <> B.x

Docker Repository Does Not Have a Release File on Running apt-get update on Ubuntu

Linux Mint 20 Ulyana users need to change "ulyana" to "bionic" in


like so:

deb [arch=amd64]    bionic    stable

What does the Excel range.Rows property really do?

It's perhaps a bit of a kludge, but the following code does what you seem to want to do:

Set rng = wks.Range(wks.Rows(iStartRow), wks.Rows(iEndRow)).Rows

Removing items from a ListBox in

Here's the code I came up with to remove items selected by a user from a listbox It seems to work ok in a multiselect listbox (selectionmode prop is set to multiextended).:

Private Sub cmdRemoveList_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles cmdRemoveList.Click
    Dim knt As Integer = lstwhatever.SelectedIndices.Count
    Dim i As Integer
    For i = 0 To knt - 1
End Sub

Android: Internet connectivity change listener

implementation 'com.treebo:internetavailabilitychecker:1.0.1'

public class MyApp extends Application {
    public void onCreate() {

    public void onLowMemory() {

raw_input function in Python

It presents a prompt to the user (the optional arg of raw_input([arg])), gets input from the user and returns the data input by the user in a string. See the docs for raw_input().


name = raw_input("What is your name? ")
print "Hello, %s." % name

This differs from input() in that the latter tries to interpret the input given by the user; it is usually best to avoid input() and to stick with raw_input() and custom parsing/conversion code.

Note: This is for Python 2.x

Pycharm: run only part of my Python file

You can select a code snippet and use right click menu to choose the action "Execute Selection in console".

How to detect scroll position of page using jQuery

Now that works for me...



    $(window).scroll(function (event) {
        var sc = $(window).scrollTop();


it works well... and then you can use JQuery/TweenMax to track elements and control them.

How to show "Done" button on iPhone number pad

The trick I've seen used is to make a custom transparent button the size of the whole view and then in its click method, have the text field resign first responder. So the user can click anywhere outside of the field to dismiss the keypad.

Why should I use an IDE?

Don't think of it as exclusive. Use the IDE for the benefits it provides, and switch to vim/preferred text editor when you need some serious focus.

I find the IDE better for refactoring and browsing and debugging and for figuring out what to do. Small things are then done right in the IDE, large things I flip to vim to finish the job.

Maven dependency for Servlet 3.0 API?

I found an example POM for the Servlet 3.0 API on DZone from September.

Suggest you use the repo, at

There are Java EE APIs in there, for example with POM that look like they might be what you're after, for example:


I'm guessing that the version conventions for the APIs have been changed to match the version of the overall EE spec (i.e. Java EE 6 vs. Servlets 3.0) as part of the new 'profiles'. Looking in the JAR, looks like all the 3.0 servlet stuff is in there. Enjoy!

Gradle Build Android Project "Could not resolve all dependencies" error

If you are running on headless CI and are installing the Android SDK through command line, make sure to include the m2repository packages in the --filter argument:

android update sdk --no-ui --filter platform-tools,build-tools-19.0.1,android-19,extra-android-support,extra-android-m2repository,extra-google-m2repository


As of Android SDK Manager rev. 22.6.4 this does not work anymore. Try this instead:

android list sdk --all

You will get a list of all available SDK packages. Look up the numerical values of the components from the first command above ("Google Repository" and others you might be missing).

Install the packages using their numerical values:

android update sdk --no-ui --all --filter <num>

Update #2 (Sept 2017)

With the "new" Android SDK tools that were released earlier this year, the android command is now deprecated, and similar functionality has been moved to a new tool called sdkmanager:

List installed components:

sdkmanager --list

Update installed components:

sdkmanager --update

Install a new component (e.g. build tools version 26.0.0):

sdkmanager 'build-tools;26.0.0'

error: the details of the application error from being viewed remotely

This can be the message you receive even when custom errors is turned off in web.config file. It can mean you have run out of free space on the drive that hosts the application. Clean your log files if you have no other space to gain on the drive.

Use of "this" keyword in C++

this points to the object in whose member function it is reffered, so it is optional.

In Go's http package, how do I get the query string on a POST request?

Below is an example:

value := r.FormValue("field")

for more info. about http package, you could visit its documentation here. FormValue basically returns POST or PUT values, or GET values, in that order, the first one that it finds.

The program can't start because api-ms-win-crt-runtime-l1-1-0.dll is missing while starting Apache server on my computer

I was facing the same issue. After many tries below solution worked for me.

Before installing VC++ install your windows updates. 1. Go to Start - Control Panel - Windows Update 2. Check for the updates. 3. Install all updates. 4. Restart your system.

After that you can follow the below steps.


Download the Visual C++ Redistributable 2015

Visual C++ Redistributable for Visual Studio 2015 (64-bit)

Visual C++ Redistributable for Visual Studio 2015 (32-bit)

(Reinstal if already installed) then restart your computer or use windows updates for download auto.

For link download

Can I use DIV class and ID together in CSS?

You can also use as many classes as needed on a tag, but an id must be unique to the document. Also be careful of using too many divs, when another more semantic tag can do the job.

<p id="unique" class="x y z">Styled paragraph</p>

How to implement linear interpolation?

Instead of extrapolating off the ends, you could return the extents of the y_list. Most of the time your application is well behaved, and the Interpolate[x] will be in the x_list. The (presumably) linear affects of extrapolating off the ends may mislead you to believe that your data is well behaved.

  • Returning a non-linear result (bounded by the contents of x_list and y_list) your program's behavior may alert you to an issue for values greatly outside x_list. (Linear behavior goes bananas when given non-linear inputs!)

  • Returning the extents of the y_list for Interpolate[x] outside of x_list also means you know the range of your output value. If you extrapolate based on x much, much less than x_list[0] or x much, much greater than x_list[-1], your return result could be outside of the range of values you expected.

    def __getitem__(self, x):
        if x <= self.x_list[0]:
            return self.y_list[0]
        elif x >= self.x_list[-1]:
            return self.y_list[-1]
            i = bisect_left(self.x_list, x) - 1
            return self.y_list[i] + self.slopes[i] * (x - self.x_list[i])

When should I use cross apply over inner join?

Consider you have two tables.


| Id   |        Name        |
|  1   |          A         |
|  2   |          B         |
|  3   |          C         |


| Id   |      PERIOD        |   QTY |
|  1   |   2014-01-13       |   10  |
|  1   |   2014-01-11       |   15  |
|  1   |   2014-01-12       |   20  |
|  2   |   2014-01-06       |   30  |
|  2   |   2014-01-08       |   40  |

There are many situations where we need to replace INNER JOIN with CROSS APPLY.

1. Join two tables based on TOP n results

Consider if we need to select Id and Name from Master and last two dates for each Id from Details table.

    FROM DETAILS D      

The above query generates the following result.

|  Id  |   Name  |   PERIOD     |  QTY  |
|   1  |   A     | 2014-01-13   |  10   |
|   1  |   A     | 2014-01-12   |  20   |

See, it generated results for last two dates with last two date's Id and then joined these records only in the outer query on Id, which is wrong. This should be returning both Ids 1 and 2 but it returned only 1 because 1 has the last two dates. To accomplish this, we need to use CROSS APPLY.


and forms the following result.

|  Id  |   Name  |   PERIOD     |  QTY  |
|   1  |   A     | 2014-01-13   |  10   |
|   1  |   A     | 2014-01-12   |  20   |
|   2  |   B     | 2014-01-08   |  40   |
|   2  |   B     | 2014-01-06   |  30   |

Here's how it works. The query inside CROSS APPLY can reference the outer table, where INNER JOIN cannot do this (it throws compile error). When finding the last two dates, joining is done inside CROSS APPLY i.e., WHERE M.ID=D.ID.

2. When we need INNER JOIN functionality using functions.

CROSS APPLY can be used as a replacement with INNER JOIN when we need to get result from Master table and a function.


And here is the function

    @Id INT 
    WHERE ID=@Id

which generated the following result

|  Id  |   Name  |   PERIOD     |  QTY  |
|   1  |   A     | 2014-01-13   |  10   |
|   1  |   A     | 2014-01-11   |  15   |
|   1  |   A     | 2014-01-12   |  20   |
|   2  |   B     | 2014-01-06   |  30   |
|   2  |   B     | 2014-01-08   |  40   |


APPLY can be used as a replacement for UNPIVOT. Either CROSS APPLY or OUTER APPLY can be used here, which are interchangeable.

Consider you have the below table(named MYTABLE).

|  Id  |   FROMDATE  |   TODATE     |
|   1  |  2014-01-11 | 2014-01-13   | 
|   1  |  2014-02-23 | 2014-02-27   | 
|   2  |  2014-05-06 | 2014-05-30   | 
|   3  |     NULL    |    NULL      |

The query is below.


which brings you the result

  | Id   |    DATES    |
  |  1   |  2014-01-11 |
  |  1   |  2014-01-13 |
  |  1   |  2014-02-23 |
  |  1   |  2014-02-27 |
  |  2   |  2014-05-06 |
  |  2   |  2014-05-30 | 
  |  3   |    NULL     | 

Default value for field in Django model

Set editable to False and default to your default value.

b = models.CharField(max_length=7, default='0000000', editable=False)

Also, your id field is unnecessary. Django will add it automatically.

CSS Disabled scrolling

overflow-x: hidden;
would hide any thing on the x-axis that goes outside of the element, so there would be no need for the horizontal scrollbar and it get removed.

overflow-y: hidden;
would hide any thing on the y-axis that goes outside of the element, so there would be no need for the vertical scrollbar and it get removed.

overflow: hidden;
would remove both scrollbars

How to resolve Unable to load authentication plugin 'caching_sha2_password' issue

This could be your connectors for MySQL which need to be updated, as MySQL8 changed the encryption of passwords - so older connectors are encrypting them incorrectly.

The maven repo for the java connector can be found here.
If you use flyway plugin, you should also consider updating it, too!

Then you can simply update your maven pom with:


Or for others who use Gradle, you can update build.gradle with:

 buildscript {
    ext {
    repositories {
    dependencies {

All that you really need to do (build.gradle example)

force css grid container to fill full screen of device

You can add position: fixed; with top left right bottom 0 attribute, that solution work on older browsers too.

If you want to embed it, add position: absolute; to the wrapper, and position: relative to the div outside of the wrapper.

.wrapper {_x000D_
  position: fixed;_x000D_
  top: 0;_x000D_
  left: 0;_x000D_
  right: 0;_x000D_
  bottom: 0;_x000D_
  display: grid;_x000D_
  border-style: solid;_x000D_
  border-color: red;_x000D_
  grid-template-columns: repeat(3, 1fr);_x000D_
  grid-template-rows: repeat(3, 1fr);_x000D_
  grid-gap: 10px;_x000D_
.one {_x000D_
  border-style: solid;_x000D_
  border-color: blue;_x000D_
  grid-column: 1 / 3;_x000D_
  grid-row: 1;_x000D_
.two {_x000D_
  border-style: solid;_x000D_
  border-color: yellow;_x000D_
  grid-column: 2 / 4;_x000D_
  grid-row: 1 / 3;_x000D_
.three {_x000D_
  border-style: solid;_x000D_
  border-color: violet;_x000D_
  grid-row: 2 / 5;_x000D_
  grid-column: 1;_x000D_
.four {_x000D_
  border-style: solid;_x000D_
  border-color: aqua;_x000D_
  grid-column: 3;_x000D_
  grid-row: 3;_x000D_
.five {_x000D_
  border-style: solid;_x000D_
  border-color: green;_x000D_
  grid-column: 2;_x000D_
  grid-row: 4;_x000D_
.six {_x000D_
  border-style: solid;_x000D_
  border-color: purple;_x000D_
  grid-column: 3;_x000D_
  grid-row: 4;_x000D_
<div class="wrapper">_x000D_
  <div class="one">One</div>_x000D_
  <div class="two">Two</div>_x000D_
  <div class="three">Three</div>_x000D_
  <div class="four">Four</div>_x000D_
  <div class="five">Five</div>_x000D_
  <div class="six">Six</div>_x000D_

Are there any style options for the HTML5 Date picker?

Currently, there is no cross browser, script-free way of styling a native date picker.

As for what's going on inside WHATWG/W3C... If this functionality does emerge, it will likely be under the CSS-UI standard or some Shadow DOM-related standard. The CSS4-UI wiki page lists a few appearance-related things that were dropped from CSS3-UI, but to be honest, there doesn't seem to be a great deal of interest in the CSS-UI module.

I think your best bet for cross browser development right now, is to implement pretty controls with JavaScript based interface, and then disable the HTML5 native UI and replace it. I think in the future, maybe there will be better native control styling, but perhaps more likely will be the ability to swap out a native control for your own Shadow DOM "widget".

It is annoying that this isn't available, and petitioning for standard support is always worthwhile. Though it does seem like jQuery UI's lead has tried and was unsuccessful.

While this is all very discouraging, it's also worth considering the advantages of the HTML5 date picker, and also why custom styles are difficult and perhaps should be avoided. On some platforms, the datepicker looks extremely different and I personally can't think of any generic way of styling the native datepicker.

Remote desktop connection protocol error 0x112f

Resized VM with more memory fixed this issue.

How can I control the width of a label tag?

You can either give class name to all label so that all can have same width :

 .class-name {  width:200px;}


.labelname{  width:200px;}

or you can simple give rest of label

label {  width:200px;  display: inline-block;}

100% width in React Native Flexbox

You should use Dimensions

First, define Dimensions.

import { Dimensions } from "react-native";

var width = Dimensions.get('window').width; //full width
var height = Dimensions.get('window').height; //full height

then, change line1 style like below:

line1: {
    backgroundColor: '#FDD7E4',
    width: width,

How do I move files in node.js?

Using the rename function:

fs.rename(getFileName, __dirname + '/new_folder/' + getFileName); 


getFilename = file.extension (old path)
__dirname + '/new_folder/' + getFileName

assumming that you want to keep the file name unchanged.

Laravel password validation rule

This doesn't quite match the OP requirements, though hopefully it helps. With Laravel you can define your rules in an easy-to-maintain format like so:

    $inputs = [
        'email'    => 'foo',
        'password' => 'bar',

    $rules = [
        'email'    => 'required|email',
        'password' => [
            'min:10',             // must be at least 10 characters in length
            'regex:/[a-z]/',      // must contain at least one lowercase letter
            'regex:/[A-Z]/',      // must contain at least one uppercase letter
            'regex:/[0-9]/',      // must contain at least one digit
            'regex:/[@$!%*#?&]/', // must contain a special character

    $validation = \Validator::make( $inputs, $rules );

    if ( $validation->fails() ) {
        print_r( $validation->errors()->all() );

Would output:

        'The email must be a valid email address.',
        'The password must be at least 10 characters.',
        'The password format is invalid.',

(The regex rules share an error message by default—i.e. four failing regex rules result in one error message)

day of the week to day number (Monday = 1, Tuesday = 2)

What about using idate()? idate()

$integer = idate('w', $timestamp);

Setting query string using Fetch GET request

var paramsdate=01+'%s'+12+'%s'+2012+'%s';


In HTML5, should the main navigation be inside or outside the <header> element?

@IanDevlin is correct. MDN's rules say the following:

"The HTML Header Element "" defines a page header — typically containing the logo and name of the site and possibly a horizontal menu..."

The word "possibly" there is key. It goes on to say that the header doesn't necessarily need to be a site header. For instance you could include a "header" on a pop-up modal or on other modular parts of the document where there is a header and it would be helpful for a user on a screen reader to know about it.

It terms of the implicit use of NAV you can use it anywhere there is grouped site navigation, although it's usually omitted from the "footer" section for mini-navs / important site links.

Really it comes down to personal / team choice. Decide what you and your team feel is more semantic and more important and the try to be consistent. For me, if the nav is inline with the logo and the main site's "h1" then it makes sense to put it in the "header" but if you have a different design choice then decide on a case by case basis.

Most importantly check out the docs and be sure if you choose to omit or include you understand why you are making that particular decision.

jQuery: Get height of hidden element in jQuery

You are confuising two CSS styles, the display style and the visibility style.

If the element is hidden by setting the visibility css style, then you should be able to get the height regardless of whether or not the element is visible or not as the element still takes space on the page.

If the element is hidden by changing the display css style to "none", then the element doesn't take space on the page, and you will have to give it a display style which will cause the element to render in some space, at which point, you can get the height.

MySQL high CPU usage

If this server is visible to the outside world, It's worth checking if it's having lots of requests to connect from the outside world (i.e. people trying to break into it)

How can I get the named parameters from a URL using Flask?

You can also use brackets <> on the URL of the view definition and this input will go into your view function arguments

def my_view_func(name):
    return name

Doctrine2: Best way to handle many-to-many with extra columns in reference table

I was getting from a conflict with join table defined in an association class ( with additional custom fields ) annotation and a join table defined in a many-to-many annotation.

The mapping definitions in two entities with a direct many-to-many relationship appeared to result in the automatic creation of the join table using the 'joinTable' annotation. However the join table was already defined by an annotation in its underlying entity class and I wanted it to use this association entity class's own field definitions so as to extend the join table with additional custom fields.

The explanation and solution is that identified by FMaz008 above. In my situation, it was thanks to this post in the forum 'Doctrine Annotation Question'. This post draws attention to the Doctrine documentation regarding ManyToMany Uni-directional relationships. Look at the note regarding the approach of using an 'association entity class' thus replacing the many-to-many annotation mapping directly between two main entity classes with a one-to-many annotation in the main entity classes and two 'many-to-one' annotations in the associative entity class. There is an example provided in this forum post Association models with extra fields:

public class Person {

  /** @OneToMany(targetEntity="AssignedItems", mappedBy="person") */
  private $assignedItems;


public class Items {

    /** @OneToMany(targetEntity="AssignedItems", mappedBy="item") */
    private $assignedPeople;

public class AssignedItems {

    /** @ManyToOne(targetEntity="Person")
    * @JoinColumn(name="person_id", referencedColumnName="id")
private $person;

    /** @ManyToOne(targetEntity="Item")
    * @JoinColumn(name="item_id", referencedColumnName="id")
private $item;


No restricted globals

Perhaps you could try passing location into the component as a prop. Below I use ...otherProps. This is the spread operator, and is valid but unneccessary if you passed in your props explicitly it's just there as a place holder for demonstration purposes. Also, research destructuring to understand where ({ location }) came from.

import React from 'react';
import withRouter from 'react-router-dom';

const MyComponent = ({ location, ...otherProps }) => (whatever you want to render)

export withRouter(MyComponent);

Laravel 5: Retrieve JSON array from $request

Just a mention with jQuery v3.2.1 and Laravel 5.6.

Case 1: The JS object posted directly, like:

$.post("url", {name:'John'}, function( data ) {

Corresponding Laravel PHP code should be:

parse_str($request->getContent(),$data); //JSON will be parsed to object $data

Case 2: The JSON string posted, like:

$.post("url", JSON.stringify({name:'John'}), function( data ) {

Corresponding Laravel PHP code should be:

$data = json_decode($request->getContent(), true);

ValidateAntiForgeryToken purpose, explanation and example

Microsoft provides us built-in functionality which we use in our application for security purposes, so no one can hack our site or invade some critical information.

From Purpose Of ValidateAntiForgeryToken In MVC Application by Harpreet Singh:

Use of ValidateAntiForgeryToken

Let’s try with a simple example to understand this concept. I do not want to make it too complicated, that’s why I am going to use a template of an MVC application, already available in Visual Studio. We will do this step by step. Let’s start.

  1. Step 1 - Create two MVC applications with default internet template and give those names as CrossSite_RequestForgery and Attack_Application respectively.

  2. Now, open CrossSite_RequestForgery application's Web Config and change the connection string with the one given below and then save.


<connectionStrings> <add name="DefaultConnection" connectionString="Data Source=local\SQLEXPRESS;Initial Catalog=CSRF;
Integrated Security=true;" providerName="System.Data.SqlClient" /> 
  1. Now, click on Tools >> NuGet Package Manager, then Package Manager Console

  2. Now, run the below mentioned three commands in Package Manager Console to create the database.

Enable-Migrations add-migration first update-database

Important Notes - I have created database with code first approach because I want to make this example in the way developers work. You can create database manually also. It's your choice.

  1. Now, open Account Controller. Here, you will see a register method whose type is post. Above this method, there should be an attribute available as [ValidateAntiForgeryToken]. Comment this attribute. Now, right click on register and click go to View. There again, you will find an html helper as @Html.AntiForgeryToken() . Comment this one also. Run the application and click on register button. The URL will be open as:


Notes- I know now the question being raised in all readers’ minds is why these two helpers need to be commented, as everyone knows these are used to validate request. Then, I just want to let you all know that this is just because I want to show the difference after and before applying these helpers.

  1. Now, open the second application which is Attack_Application. Then, open Register method of Account Controller. Just change the POST method with the simple one, shown below.

    Registration Form
    1. @Html.LabelFor(m => m.UserName) @Html.TextBoxFor(m => m.UserName)
    2. @Html.LabelFor(m => m.Password) @Html.PasswordFor(m => m.Password)
    3. @Html.LabelFor(m => m.ConfirmPassword) @Html.PasswordFor(m => m.ConfirmPassword)

7.Now, suppose you are a hacker and you know the URL from where you can register user in CrossSite_RequestForgery application. Now, you created a Forgery site as Attacker_Application and just put the same URL in post method.

8.Run this application now and fill the register fields and click on register. You will see you are registered in CrossSite_RequestForgery application. If you check the database of CrossSite_RequestForgery application then you will see and entry you have entered.

  1. Important - Now, open CrossSite_RequestForgery application and comment out the token in Account Controller and register the View. Try to register again with the same process. Then, an error will occur as below.

Server Error in '/' Application. ________________________________________ The required anti-forgery cookie "__RequestVerificationToken" is not present.

This is what the concept says. What we add in View i.e. @Html.AntiForgeryToken() generates __RequestVerificationToken on load time and [ValidateAntiForgeryToken] available on Controller method. Match this token on post time. If token is the same, then it means this is a valid request.

How to check if a specific key is present in a hash or not?

Another way is here

hash = {one: 1, two: 2}

#=> true

#=> false

Test file upload using HTTP PUT method

For curl, how about using the -d switch? Like: curl -X PUT "localhost:8080/urlstuffhere" -d "@filename"?

_tkinter.TclError: no display name and no $DISPLAY environment variable

You can solve it by adding these two lines in the VERY beginning of your .py script.

import matplotlib

PS: The error will still exists if these two lines are not added in the very beginning of the source code.

Should Jquery code go in header or footer?

Just before </body> is the best place according to Yahoo Developer Network's Best Practices for Speeding Up Your Web Site this link, it makes sense.

The best thing to do is to test by yourself.

WPF global exception handler

Best answer is probably

Here is some code that shows how to use it:


public sealed partial class App
    protected override void OnStartup(StartupEventArgs e)
        // setting up the Dependency Injection container
        var resolver = ResolverFactory.Get();

        // getting the ILogger or ILog interface
        var logger = resolver.Resolve<ILogger>();

        // Bootstrapping Dependency Injection 
        // injects ViewModel into MainWindow.xaml
        // remember to remove the StartupUri attribute in App.xaml
        var mainWindow = resolver.Resolve<Pages.MainWindow>();

    private void RegisterGlobalExceptionHandling(ILogger log)
        // this is the line you really want 
        AppDomain.CurrentDomain.UnhandledException += 
            (sender, args) => CurrentDomainOnUnhandledException(args, log);

        // optional: hooking up some more handlers
        // remember that you need to hook up additional handlers when 
        // logging from other dispatchers, shedulers, or applications

        Application.Dispatcher.UnhandledException += 
            (sender, args) => DispatcherOnUnhandledException(args, log);

        Application.Current.DispatcherUnhandledException +=
            (sender, args) => CurrentOnDispatcherUnhandledException(args, log);

        TaskScheduler.UnobservedTaskException += 
            (sender, args) => TaskSchedulerOnUnobservedTaskException(args, log);

    private static void TaskSchedulerOnUnobservedTaskException(UnobservedTaskExceptionEventArgs args, ILogger log)
        log.Error(args.Exception, args.Exception.Message);

    private static void CurrentOnDispatcherUnhandledException(DispatcherUnhandledExceptionEventArgs args, ILogger log)
        log.Error(args.Exception, args.Exception.Message);
        // args.Handled = true;

    private static void DispatcherOnUnhandledException(DispatcherUnhandledExceptionEventArgs args, ILogger log)
        log.Error(args.Exception, args.Exception.Message);
        // args.Handled = true;

    private static void CurrentDomainOnUnhandledException(UnhandledExceptionEventArgs args, ILogger log)
        var exception = args.ExceptionObject as Exception;
        var terminatingMessage = args.IsTerminating ? " The application is terminating." : string.Empty;
        var exceptionMessage = exception?.Message ?? "An unmanaged exception occured.";
        var message = string.Concat(exceptionMessage, terminatingMessage);
        log.Error(exception, message);

Left-pad printf with spaces

If you want the word "Hello" to print in a column that's 40 characters wide, with spaces padding the left, use the following.

char *ptr = "Hello";
printf("%40s\n", ptr);

That will give you 35 spaces, then the word "Hello". This is how you format stuff when you know how wide you want the column, but the data changes (well, it's one way you can do it).

If you know you want exactly 40 spaces then some text, just save the 40 spaces in a constant and print them. If you need to print multiple lines, either use multiple printf statements like the one above, or do it in a loop, changing the value of ptr each time.

iOS 8 removed "minimal-ui" viewport property, are there other "soft fullscreen" solutions?

The root problem here seems that iOS8 safari won't hide the address bar when scrolling down if the content is equal or less than the viewport.

As you found out already, adding some padding at the bottom gets around this issue:

html {
    /* enough space to scroll up to get fullscreen on iOS8 */
    padding-bottom: 80px;
// sort of emulate safari's "bounce back to top" scroll
window.addEventListener('scroll', function(ev) {
    // avoids scrolling when the focused element is e.g. an input
    if (
        || document.activeElement === document.body
    ) {

The above css should be conditionally applied, for example with UA sniffing adding a gt-ios8 class to <html>.

How to overload __init__ method based on argument type?

Why don't you go even more pythonic?

class AutoList:
def __init__(self, inp):
    try:                        ## Assume an opened-file... =
    except AttributeError:
        try:                    ## Assume an existent filename...
            with open(inp, 'r') as fd:
   = inp     ## Who cares what that might be?

Where do I find the current C or C++ standard documents?

C99 is available online. Quoted from

The lastest publically available version of the standard is the combined C99 + TC1 + TC2 + TC3, WG14 N1256, dated 2007-09-07. This is a WG14 working paper, but it reflects the consolidated standard at the time of issue.

How does database indexing work?

An index is just a data structure that makes the searching faster for a specific column in a database. This structure is usually a b-tree or a hash table but it can be any other logic structure.

Stopping a thread after a certain amount of time

This will work if you are not blocking.

If you are planing on doing sleeps, its absolutely imperative that you use the event to do the sleep. If you leverage the event to sleep, if someone tells you to stop while "sleeping" it will wake up. If you use time.sleep() your thread will only stop after it wakes up.

import threading
import time

duration = 2

def main():
    t1_stop = threading.Event()
    t1 = threading.Thread(target=thread1, args=(1, t1_stop))

    t2_stop = threading.Event()
    t2 = threading.Thread(target=thread2, args=(2, t2_stop))

    # stops thread t2

def thread1(arg1, stop_event):
    while not stop_event.is_set():

def thread2(arg1, stop_event):
    while not stop_event.is_set():

Create or update mapping in elasticsearch

Generally speaking, you can update your index mapping using the put mapping api (reference here) :

curl -XPUT 'http://localhost:9200/advert_index/_mapping/advert_type' -d '
    "advert_type" : {
        "properties" : {

          //your new mapping properties


It's especially useful for adding new fields. However, in your case, you will try to change the location type, which will cause a conflict and prevent the new mapping from being used.

You could use the put mapping api to add another property containing the location as a lat/lon array, but you won't be able to update the previous location field itself.

Finally, you will have to reindex your data for your new mapping to be taken into account.

The best solution would really be to create a new index.

If your problem with creating another index is downtime, you should take a look at aliases to make things go smoothly.

Is it possible to use a div as content for Twitter's Popover

In addition to other replies. If you allow html in options you can pass jQuery object to content, and it will be appended to popover's content with all events and bindings. Here is the logic from source code:

  • if you pass a function it will be called to unwrap content data
  • if html is not allowed content data will be applied as text
  • if html allowed and content data is string it will be applied as html
  • otherwise content data will be appended to popover's content container
    content: $("#popover-content"),
    html: true,
    title: "Popover title"

Bootstrap carousel multiple frames at once

Can this be done with bootstrap 3's carousel? I'm hoping I won't have to go hunting for yet another jQuery plugin

As of 2013-12-08 the answer is no. The effect you are looking for is not possible using Bootstrap 3's generic carousel plugin. However, here's a simple jQuery plugin that seems to do exactly what you want

Python Iterate Dictionary by Index

Do this:

for i in dict.keys():

kill a process in bash

To interrupt it, you can try pressing ctrl c to send a SIGINT. If it doesn't stop it, you may try to kill it using kill -9 <pid>, which sends a SIGKILL. The latter can't be ignored/intercepted by the process itself (the one being killed).

To move the active process to background, you can press ctrl z. The process is sent to background and you get back to the shell prompt. Use the fg command to do the opposite.

Clear text in EditText when entered

It's simple: declare the widget variables (editText, textView, button etc.) in class but initialize it in onCreate after setContentView.

The problem is when you try to access a widget of a layout first you have to declare the layout. Declaring the layout is setContentView. And when you initialize the widget variable via findViewById you are accessing the id of the widget in the main layout in the setContentView.

I hope you get it!

Close a MessageBox after several seconds

You could try this:

[DllImport("user32.dll", EntryPoint="FindWindow", SetLastError = true)]
static extern IntPtr FindWindowByCaption(IntPtr ZeroOnly, string lpWindowName);

static extern int PostMessage(IntPtr hWnd, UInt32 msg, int wParam, int lParam);

private const UInt32 WM_CLOSE = 0x0010;

public void ShowAutoClosingMessageBox(string message, string caption)
    var timer = new System.Timers.Timer(5000) { AutoReset = false };
    timer.Elapsed += delegate
        IntPtr hWnd = FindWindowByCaption(IntPtr.Zero, caption);
        if (hWnd.ToInt32() != 0) PostMessage(hWnd, WM_CLOSE, 0, 0);
    timer.Enabled = true;
    MessageBox.Show(message, caption);

How to check whether a select box is empty using JQuery/Javascript

To check whether select box has any values:

if( $('#fruit_name').has('option').length > 0 ) {

To check whether selected value is empty:

if( !$('#fruit_name').val() ) { 

What is an idempotent operation?

In short, Idempotent operations means that the operation will not result in different results no matter how many times you operate the idempotent operations.

For example, according to the definition of the spec of HTTP, GET, HEAD, PUT, and DELETE are idempotent operations; however POST and PATCH are not. That's why sometimes POST is replaced by PUT.

How to write a SQL DELETE statement with a SELECT statement in the WHERE clause?

Shouldn't you have:

DELETE FROM tableA WHERE entitynum IN (...your select...)

Now you just have a WHERE with no comparison:

DELETE FROM tableA WHERE (...your select...)

So your final query would look like this;

DELETE FROM tableA WHERE entitynum IN (
    SELECT tableA.entitynum FROM tableA q
      INNER JOIN tableB u on (u.qlabel = q.entityrole AND u.fieldnum = q.fieldnum) 
    WHERE (LENGTH(q.memotext) NOT IN (8,9,10) OR q.memotext NOT LIKE '%/%/%')
      AND (u.FldFormat = 'Date')

How to return Json object from MVC controller to view

You could use AJAX to call this controller action. For example if you are using jQuery you might use the $.ajax() method:

<script type="text/javascript">
        url: '@Url.Action("NameOfYourAction")',
        type: 'GET',
        cache: false,
        success: function(result) {
            // you could use the result.values dictionary here

How do I run a PowerShell script when the computer starts?

Copy ps1 into this folder, and create it if necessary. It will run at every start-up (before user logon occurs).


Also it can be done through GPEDIT.msc if available on your OS build (lower level OS maybe not).

jquery change class name

You can do This : $("#td_id").removeClass('Old_class'); $("#td_id").addClass('New_class'); Or You can do This


How to mark a method as obsolete or deprecated?

Add an annotation to the method using the keyword Obsolete. Message argument is optional but a good idea to communicate why the item is now obsolete and/or what to use instead.

[System.Obsolete("use myMethodB instead")]
void myMethodA()

How to remove any URL within a string in Python

import re
s = '''
g = re.findall(r'(text\d+)',s)
print ('list',g)
for i in g:
    print (i)


list ['text1', 'text2', 'text3', 'text4', 'text5', 'text6']
text6    ?

Send data from activity to fragment in Android

the better approach for sending data from activity class to fragment is passing via setter methods. Like

FragmentClass fragmentClass = new FragmentClass();

and get these data from the class easily.

What does the "~" (tilde/squiggle/twiddle) CSS selector mean?

Good to also check the other combinators in the family and to get back to what is this specific one.

  • ul li
  • ul > li
  • ul + ul
  • ul ~ ul

Example checklist:

  • ul li - Looking inside - Selects all the li elements placed (anywhere) inside the ul; Descendant selector
  • ul > li - Looking inside - Selects only the direct li elements of ul; i.e. it will only select direct children li of ul; Child Selector or Child combinator selector
  • ul + ul - Looking outside - Selects the ul immediately following the ul; It is not looking inside, but looking outside for the immediately following element; Adjacent Sibling Selector
  • ul ~ ul - Looking outside - Selects all the ul which follows the ul doesn't matter where it is, but both ul should be having the same parent; General Sibling Selector

The one we are looking at here is General Sibling Selector

Import Script from a Parent Directory

You don't import scripts in Python you import modules. Some python modules are also scripts that you can run directly (they do some useful work at a module-level).

In general it is preferable to use absolute imports rather than relative imports.

+-- subpackage

In moduleB:

from toplevel_package import moduleA

If you'd like to run as a script then make sure that parent directory for toplevel_package is in your sys.path.

SQL Server : export query as a .txt file

The BCP Utility can also be used in the form of a .bat file, but be cautious of escape sequences (ie quotes "" must be used in conjunction with ) and the appropriate tags.

.bat Example:

bcp "\"YOUR_SERVER\".dbo.Proc" queryout C:\FilePath.txt -T -c -q
-- Add PAUSE here if you'd like to see the completed batch

-q MUST be used in the presence of quotations within the query itself.

BCP can also run Stored Procedures if necessary. Again, be cautious: Temporary Tables must be created prior to execution or else you should consider using Table Variables.

How to compare dates in datetime fields in Postgresql?

When you compare update_date >= '2013-05-03' postgres casts values to the same type to compare values. So your '2013-05-03' was casted to '2013-05-03 00:00:00'.

So for update_date = '2013-05-03 14:45:00' your expression will be that:

'2013-05-03 14:45:00' >= '2013-05-03 00:00:00' AND '2013-05-03 14:45:00' <= '2013-05-03 00:00:00'

This is always false

To solve this problem cast update_date to date:

select * from table where update_date::date >= '2013-05-03' AND update_date::date <= '2013-05-03' -> Will return result

Best way to track onchange as-you-type in input type="text"?

Use oninput instead of onchange.


    <title>title here</title>
    <script src="index.js"></script>
    <input oninput="onclickhandler(this)"></input>


function onclickhandler(e) {

VB.NET: Clear DataGridView

For the Clear of Grid View Data You Have to clear the dataset or Datatable

I use this Code I clear the Grid View Data even if re submit again and again it will work Example Dim con As New OleDbConnection Dim cmd As New OleDbCommand Dim da As New OleDbDataAdapter Dim dar As OleDbDataReader Dim dt As New DataTable If (con.State <> 1) Then con.Open() End If dt.Clear() 'To clear Data Every time to fresh data cmd.Connection = con cmd.CommandText = "select * from users" da.SelectCommand = cmd da.Fill(dt) DataGridView1.DataSource = dt DataGridView1.Visible = True


Bootstrap Carousel Full Screen

I found an answer on the Try this code:


body {
    height: 100%;

.active {
    height: 100%;

.carousel-inner {
    height: 100%;

/* Background images are set within the HTML using inline CSS, not here */

.fill {
    width: 100%;
    height: 100%;
    background-position: center;
    -webkit-background-size: cover;
    -moz-background-size: cover;
    background-size: cover;
    -o-background-size: cover;

footer {
    margin: 50px 0;


   <div class="carousel-inner">
        <div class="item active">
            <!-- Set the first background image using inline CSS below. -->
            <div class="fill" style="background-image:url(' One');"></div>
            <div class="carousel-caption">
                <h2>Caption 1</h2>
        <div class="item">
            <!-- Set the second background image using inline CSS below. -->
            <div class="fill" style="background-image:url(' Two');"></div>
            <div class="carousel-caption">
                <h2>Caption 2</h2>
        <div class="item">
            <!-- Set the third background image using inline CSS below. -->
            <div class="fill" style="background-image:url(' Three');"></div>
            <div class="carousel-caption">
                <h2>Caption 3</h2>


Can we rely on String.isEmpty for checking null condition on a String in Java?

No, the String.isEmpty() method looks as following:

public boolean isEmpty() {
    return this.value.length == 0;

as you can see it checks the length of the string so you definitely have to check if the string is null before.

Golang append an item to a slice

NOTICE that append generates a new slice if cap is not sufficient. @kostix's answer is correct, or you can pass slice argument by pointer!

What is the maximum recursion depth in Python, and how to increase it?

If you want to get only few Fibonacci numbers, you can use matrix method.

from numpy import matrix

def fib(n):
    return (matrix('0 1; 1 1', dtype='object') ** n).item(1)

It's fast as numpy uses fast exponentiation algorithm. You get answer in O(log n). And it's better than Binet's formula because it uses only integers. But if you want all Fibonacci numbers up to n, then it's better to do it by memorisation.

Call a function from another file?

Came across the same feature but I had to do the below to make it work.

If you are seeing 'ModuleNotFoundError: No module named', you probably need the dot(.) in front of the filename as below;

from .file import funtion

Sorting multiple keys with Unix sort

The -k option is what you want.

-k 1.4,1.5n -k 1.14,1.15n

Would use character positions 4-5 in the first field (it's all one field for fixed width) and sort numerically as the first key.

The second key would be characters 14-15 in the first field also.


Example (all I have is DOS/cygwin handy):

dir | \cygwin\bin\sort.exe -k 1.4,1.5n -k 1.40,1.60r

for the data:

12/10/2008  01:10 PM         1,564,990 outfile.txt

Sorts the directory listing by month number (pos 4-5) numerically, and then by filename (pos 40-60) in reverse. Since there are no tabs, it's all field 1 to sort.

Open a link in browser with java button?

public static void openWebPage(String url) {
    try {
        Desktop desktop = Desktop.isDesktopSupported() ? Desktop.getDesktop() : null;
        if (desktop != null && desktop.isSupported(Desktop.Action.BROWSE)) {
            desktop.browse(new URI(url));
        throw new NullPointerException();
    } catch (Exception e) {
        JOptionPane.showMessageDialog(null, url, "", JOptionPane.PLAIN_MESSAGE);

How to read existing text files without defining path

You need to decide which directory you want the file to be relative to. Once you have done that, you construct the full path like this:

string fullPathToFile = Path.Combine(dir, fileName);

If you don't supply the base directory dir then you will be at the total mercy of whatever happens to the working directory of your process. That is something that can be out of your control. For example, shortcuts to your application may specify it. Using file dialogs can change it.

For a console application it is reasonable to use relative files directly because console applications are designed so that the working directory is a critical input and is a well-defined part of the execution environment. However, for a GUI app that is not the case which is why I recommend you explicitly convert your relative file name to a full absolute path using some well-defined base directory.

Now, since you have a console application, it is reasonable for you to use a relative path, provided that the expectation is that the files in question will be located in the working directory. But it would be very common for that not to be the case. Normally the working directory is used to specify where the user's input and output files are to be stored. It does not typically point to the location where the program's files are.

One final option is that you don't attempt to deploy these program files as external text files. Perhaps a better option is to link them to the executable as resources. That way they are bound up with the executable and you can completely side-step this issue.

How do I debug "Error: spawn ENOENT" on node.js?

@laconbass's answer helped me and is probably most correct.

I came here because I was using spawn incorrectly. As a simple example:

this is incorrect:

const s = cp.spawn('npm install -D suman', [], {
    cwd: root

this is incorrect:

const s = cp.spawn('npm', ['install -D suman'], {
    cwd: root

this is correct:

const s = cp.spawn('npm', ['install','-D','suman'], {
    cwd: root

however, I recommend doing it this way:

const s = cp.spawn('bash');
s.stdin.end(`cd "${root}" && npm install -D suman`);
s.once('exit', code => {
   // exit

this is because then the cp.on('exit', fn) event will always fire, as long as bash is installed, otherwise, the cp.on('error', fn) event might fire first, if we use it the first way, if we launch 'npm' directly.

How can I fill a column with random numbers in SQL? I get the same value in every row


//rand(1000000 , 9999999);

$products_query = "SELECT id FROM products";
$products_result = mysqli_query($conn, $products_query);
$products_row = mysqli_fetch_array($products_result);
$ids_array = [];

    array_push($ids_array, $products_row['id']);
while($products_row = mysqli_fetch_array($products_result));

echo '<pre>';
echo '</pre>';
$row_counter = count($ids_array);

for ($i=0; $i < $row_counter; $i++)
    $current_row = $ids_array[$i];
    $rand = rand(1000000 , 9999999);
    mysqli_query($conn , "UPDATE products SET code='$rand' WHERE id='$current_row'");

How to minify php page html output?

Create a PHP file outside your document root. If your document root is


create the a file named minify.php one level above it


Copy paste the following PHP code into it

function minify_output($buffer){
    $search = array('/\>[^\S ]+/s','/[^\S ]+\</s','/(\s)+/s');
    $replace = array('>','<','\\1');
    if (preg_match("/\<html/i",$buffer) == 1 && preg_match("/\<\/html\>/i",$buffer) == 1) {
        $buffer = preg_replace($search, $replace, $buffer);
    return $buffer;

Save the minify.php file and open the php.ini file. If it is a dedicated server/VPS search for the following option, on shared hosting with custom php.ini add it.

auto_prepend_file = /var/www/minify.php


Creating a batch file, for simple javac and java command execution

you want these four lines of code in your Run.bat:

@echo off          //this makes it so you have an empty cmd window on startup
javac    //this compiles the .java into a .class
java Main          // this runs the .class file
pause              //this prevents the window from instantly closing after program end

jQuery UI DatePicker to show month year only

Thanks for Ben Koehler's solution.

However, I had a problem with multiple instances of datepickers, with some of them needed with day selection. Ben Koehler's solution (in edit 3) works, but hides the day selection in all instances. Here's an update that solves this issue :

    dateFormat: "mm/yy",
    changeMonth: true,
    changeYear: true,
    showButtonPanel: true,
    onClose: function(dateText, inst) {
        if($('#ui-datepicker-div').html().indexOf('ui-datepicker-close ui-state-default ui-priority-primary ui-corner-all ui-state-hover') > -1) {
                new Date(
                    $("#ui-datepicker-div .ui-datepicker-year :selected").val(),
                    $("#ui-datepicker-div .ui-datepicker-month :selected").val(),
    beforeShow : function(input, inst) {
        if((datestr = $(this).val()).length > 0) {
            year = datestr.substring(datestr.length-4, datestr.length);
            month = datestr.substring(0, 2);
            $(this).datepicker('option', 'defaultDate', new Date(year, month-1, 1));
            $(this).datepicker('setDate', new Date(year, month-1, 1));

How do I enable --enable-soap in php on linux?

As far as your question goes: no, if activating from .ini is not enough and you can't upgrade PHP, there's not much you can do. Some modules, but not all, can be added without recompilation (zypper install php5-soap, yum install php-soap). If it is not enough, try installing some PEAR class for interpreted SOAP support (NuSOAP, etc.).

In general, the double-dash --switches are designed to be used when recompiling PHP from scratch.

You would download the PHP source package (as a compressed .tgz tarball, say), expand it somewhere and then, e.g. under Linux, run the configure script

./configure --prefix ...

The configure command used by your PHP may be shown with phpinfo(). Repeating it identical should give you an exact copy of the PHP you now have installed. Adding --enable-soap will then enable SOAP in addition to everything else.

That said, if you aren't familiar with PHP recompilation, don't do it. It also requires several ancillary libraries that you might, or might not, have available - freetype, gd, libjpeg, XML, expat, and so on and so forth (it's not enough they are installed; they must be a developer version, i.e. with headers and so on; in most distributions, having libjpeg installed might not be enough, and you might need libjpeg-dev also).

I have to keep a separate virtual machine with everything installed for my recompilation purposes.

How to refresh token with Google API client?

Had the same issue; my script that worked yesterday, for some odd reason did not today. No changes.

Apparently this was because my system clock was off by 2.5 (!!) seconds, syncing with NTP fixed it.

See also:

How to add app icon within phonegap projects?

Fortunately there is a little bit in the docs about the splash images, which put me on the road to getting the right location for the icon images as well. So here it goes.

Where the files are placed Once you have built your project using command-line interface "cordova build ios" you should have a complete file structure for your iOS app in the platforms/ios/ folder.

Inside that folder is a folder with the name of your app. Which in turn contains a resources/ directory where you will find the icons/ and splashscreen/ folders.

In the icons folder you will find four icon files (for 57px and 72 px, each in regular and @2x version). These are the Phonegap placeholder icons you've been seeing so far.

What to do

All you have to do is save the icon files in this folder. So that's:


Same for splashscreen files.


  1. After placing the files there, rebuild the project using cordova build ios AND use xCode's 'Clean product' menu command. Without this, you'll still be seeing the Phonegap placeholders.

  2. It's wisest to rename your files the iOS/Apple way (i.e. [email protected] etc) instead of editing the names in the info.plist or config.xml. At least that worked for me.

  3. And by the way, ignore the weird path and the weird filename given for the icons in config.xml (i.e. <icon gap:platform="ios" height="114" src="res/icon/ios/icon-57-2x.png" width="114" />). I just left those definitions there, and the icons showed up just fine even though my 114px icon was named [email protected] instead of icon-57-2x.png.

  4. Don't use config.xml to prevent Apple's gloss effect on the icon. Instead, tick the box in xCode (click the project title in the left navigation column, select your app under the Target header, and scroll down to the icons section).

Can I pass a JavaScript variable to another browser window?

Yes, scripts can access properties of other windows in the same domain that they have a handle on (typically gained through and window.frames/parent). It is usually more manageable to call functions defined on the other window rather than fiddle with variables directly.

However, windows can die or move on, and browsers deal with it differently when they do. Check that a window (a) is still open (!window.closed) and (b) has the function you expect available, before you try to call it.

Simple values like strings are fine, but generally it isn't a good idea to pass complex objects such as functions, DOM elements and closures between windows. If a child window stores an object from its opener, then the opener closes, that object can become 'dead' (in some browsers such as IE), or cause a memory leak. Weird errors can ensue.

How to check if user input is not an int value

you have following errors which in turn is causing you that exception, let me explain it

this is your existing code:

if(!scan.hasNextInt()) {
        System.out.println("Invalid input!");
        System.out.print("Enter an integer: ");
        usrInput= sc.nextInt();

in the above code if(!scan.hasNextInt()) will become true only when user input contains both characters as well as integers like your input adfd 123.

but you are trying to read only integers inside the if condition using usrInput= sc.nextInt();. Which is incorrect,that's what is throwing Exception in thread "main" java.util.InputMismatchException.

so correct code should be

 if(!scan.hasNextInt()) {
            System.out.println("Invalid input!");
            System.out.print("Enter an integer: ");

in the above code will help to read new input from user and continue will help in executing same if condition(i.e if(!scan.hasNextInt())) again.

Please use code in my first answer to build your complete logic.let me know if you need any explanation on it.

Dynamic creation of table with DOM

You can create a dynamic table rows as below:

var tbl = document.createElement('table'); = '100%';

for (var i = 0; i < files.length; i++) {

        tr = document.createElement('tr');

        var td1 = document.createElement('td');
        var td2 = document.createElement('td');
        var td3 = document.createElement('td');

        ::::: // As many <td> you want




How to get correlation of two vectors in python

The docs indicate that numpy.correlate is not what you are looking for:

numpy.correlate(a, v, mode='valid', old_behavior=False)[source]
  Cross-correlation of two 1-dimensional sequences.
  This function computes the correlation as generally defined in signal processing texts:
     z[k] = sum_n a[n] * conj(v[n+k])
  with a and v sequences being zero-padded where necessary and conj being the conjugate.

Instead, as the other comments suggested, you are looking for a Pearson correlation coefficient. To do this with scipy try:

from scipy.stats.stats import pearsonr   
a = [1,4,6]
b = [1,2,3]   
print pearsonr(a,b)

This gives

(0.99339926779878274, 0.073186395040328034)

You can also use numpy.corrcoef:

import numpy
print numpy.corrcoef(a,b)

This gives:

[[ 1.          0.99339927]
 [ 0.99339927  1.        ]]

What does print(... sep='', '\t' ) mean?

sep='' in the context of a function call sets the named argument sep to an empty string. See the print() function; sep is the separator used between multiple values when printing. The default is a space (sep=' '), this function call makes sure that there is no space between Property tax: $ and the formatted tax floating point value.

Compare the output of the following three print() calls to see the difference

>>> print('foo', 'bar')
foo bar
>>> print('foo', 'bar', sep='')
>>> print('foo', 'bar', sep=' -> ')
foo -> bar

All that changed is the sep argument value.

\t in a string literal is an escape sequence for tab character, horizontal whitespace, ASCII codepoint 9.

\t is easier to read and type than the actual tab character. See the table of recognized escape sequences for string literals.

Using a space or a \t tab as a print separator shows the difference:

>>> print('eggs', 'ham')
eggs ham
>>> print('eggs', 'ham', sep='\t')
eggs    ham

HTML not loading CSS file

This may be a 'special' case but was fiddling with this piece of code:

ForceType application/x-httpd-php SetHandler application/x-httpd-php

As a quick test for extentionless file handling, when a similar problem occurred.

Some but not all php files thereafter treated the css files as php and thus succesfully loaded the css but not handled it as css, thus zero rules were executed when checking f12 style editor.

Perhaps something similar might occur to any-one else here and this tidbit might help.

How to make a flex item not fill the height of the flex container?

When you create a flex container various default flex rules come into play.

Two of these default rules are flex-direction: row and align-items: stretch. This means that flex items will automatically align in a single row, and each item will fill the height of the container.

If you don't want flex items to stretch – i.e., like you wrote:

make its height the minimum required for holding its content

... then simply override the default with align-items: flex-start.

#a {_x000D_
  display: flex;_x000D_
  align-items: flex-start; /* NEW */_x000D_
#a > div {_x000D_
  background-color: red;_x000D_
  padding: 5px;_x000D_
  margin: 2px;_x000D_
#b {_x000D_
  height: auto;_x000D_
<div id="a">_x000D_
  <div id="b">left</div>_x000D_

Here's an illustration from the flexbox spec that highlights the five values for align-items and how they position flex items within the container. As mentioned before, stretch is the default value.

enter image description here Source: W3C

How to execute a * .PY file from a * .IPYNB file on the Jupyter notebook?

the below lines would also work


How to use Ajax.ActionLink?

@Ajax.ActionLink requires jQuery AJAX Unobtrusive library. You can download it via nuget:

Install-Package Microsoft.jQuery.Unobtrusive.Ajax

Then add this code to your View:


Create an ArrayList with multiple object types?

I am also newish to Java and just figured this out. You should create your own class which stores the string and integer, and then make a list of these objects. For instance (I am sure this code is imperfect, but better than arrayList):

class Stuff {
    private String label;
    private Integer value;

    // Constructor or setter
    public void Stuff(String label, Integer value) {
        if (label == null || value == null) {
        this.label = label;
        this.value = value;

    // getters

    public String getLabel() {
        return this.label;

    public Integer getValue() {
        return this.value;

Then in your code:

private ArrayList<Stuff> items = new ArrayList<Stuff>();
items.add(new Stuff(label, value));

for (Stuff item: items) {
     doSomething(item.getLabel()); // returns String
     doSomething(item.getValue()); // returns Integer

Eliminating NAs from a ggplot

Just an update to the answer of @rafa.pereira. Since ggplot2 is part of tidyverse, it makes sense to use the convenient tidyverse functions to get rid of NAs.

airquality %>% 
        drop_na(Ozone) %>%
        ggplot(aes(x = Ozone))+

Note that you can also use drop_na() without columns specification; then all the rows with NAs in any column will be removed.

Setting the height of a DIV dynamically

inspired by @jason-bunting, same thing for either height or width:

function resizeElementDimension(element, doHeight) {
  dim = (doHeight ? 'Height' : 'Width')
  ref = (doHeight ? 'Top' : 'Left')

  var x = 0;
  var body = window.document.body;
  if(window['inner' + dim])
    x = window['inner' + dim]
  else if (body.parentElement['client' + dim])
    x = body.parentElement['client' + dim]
  else if (body && body['client' + dim])
    x = body['client' + dim][dim.toLowerCase()] = ((x - element['offset' + ref]) + "px");

All combinations of a list of lists

you need itertools.product:

>>> import itertools
>>> a = [[1,2,3],[4,5,6],[7,8,9,10]]
>>> list(itertools.product(*a))
[(1, 4, 7), (1, 4, 8), (1, 4, 9), (1, 4, 10), (1, 5, 7), (1, 5, 8), (1, 5, 9), (1, 5, 10), (1, 6, 7), (1, 6, 8), (1, 6, 9), (1, 6, 10), (2, 4, 7), (2, 4, 8), (2, 4, 9), (2, 4, 10), (2, 5, 7), (2, 5, 8), (2, 5, 9), (2, 5, 10), (2, 6, 7), (2, 6, 8), (2, 6, 9), (2, 6, 10), (3, 4, 7), (3, 4, 8), (3, 4, 9), (3, 4, 10), (3, 5, 7), (3, 5, 8), (3, 5, 9), (3, 5, 10), (3, 6, 7), (3, 6, 8), (3, 6, 9), (3, 6, 10)]

Can you autoplay HTML5 videos on the iPad?

iOS 10 update

The ban on autoplay has been lifted as of iOS 10 - but with some restrictions (e.g. A can be autoplayed if there is no audio track).

To see a full list of these restrictions, see the official docs:

iOS 9 and before

As of iOS 6.1, it is no longer possible to auto-play videos on the iPad.

My assumption as to why they've disabled the auto-play feature?

Well, as many device owners have data usage/bandwidth limits on their devices, I think Apple felt that the user themselves should decide when they initiate bandwidth usage.

After a bit of research I found the following extract in the Apple documentation in regard to auto-play on iOS devices to confirm my assumption:

"Apple has made the decision to disable the automatic playing of video on iOS devices, through both script and attribute implementations.

In Safari, on iOS (for all devices, including iPad), where the user may be on a cellular network and be charged per data unit, preload and auto-play are disabled. No data is loaded until the user initiates it." - Apple documentation.

Here is a separate warning featured on the Safari HTML5 Reference page about why embedded media cannot be played in Safari on iOS:

Warning: To prevent unsolicited downloads over cellular networks at the user’s expense, embedded media cannot be played automatically in Safari on iOS—the user always initiates playback. A controller is automatically supplied on iPhone or iPod touch once playback in initiated, but for iPad you must either set the controls attribute or provide a controller using JavaScript.

What this means (in terms of code) is that Javascript's play() and load() methods are inactive until the user initiates playback, unless the play() or load() method is triggered by user action (e.g. a click event).

Basically, a user-initiated play button works, but an onLoad="play()" event does not.

For example, this would play the movie:

<input type="button" value="Play" onclick="">

Whereas the following would do nothing on iOS:

<body onload="">

SQL Logic Operator Precedence: And and Or

Query to show a 3-variable boolean expression truth table :

;WITH cteData AS
(SELECT 0 AS A, 0 AS B, 0 AS C
SELECT cteData.*,

(A=1) OR (B=1) AND (C=1)

    THEN 'True' ELSE 'False' END AS Result
FROM cteData

Results for (A=1) OR (B=1) AND (C=1) :

A   B   C   Result
0   0   0   False
0   0   1   False
0   1   0   False
0   1   1   True
1   0   0   True
1   0   1   True
1   1   0   True
1   1   1   True

Results for (A=1) OR ( (B=1) AND (C=1) ) are the same.

Results for ( (A=1) OR (B=1) ) AND (C=1) :

A   B   C   Result
0   0   0   False
0   0   1   False
0   1   0   False
0   1   1   True
1   0   0   False
1   0   1   True
1   1   0   False
1   1   1   True

Android ClassNotFoundException: Didn't find class on path

1) Create libs folder under project root
2) Copy and paste the jar file into it
3) Configure the build path (Add jar)
4) Clean and run

cheers :-)

document.getElementById vs jQuery $()

Close, but not the same. They're getting the same element, but the jQuery version is wrapped in a jQuery object.

The equivalent would be this

var contents = $('#contents').get(0);

or this

var contents = $('#contents')[0];

These will pull the element out of the jQuery object.

What is Java Servlet?

I think servlet is basically a java class which acts as a middle way between HTTP request and HTTP response.Servlet is also used to make your web page dynamic. Suppose for example if you want to redirect to another web page on server then you have to use servlets. Another important thing is that servlet can run on localhost as well as a web browser.

How to import a SQL Server .bak file into MySQL?

The .BAK files from SQL server are in Microsoft Tape Format (MTF) ref:

The bak file will probably contain the LDF and MDF files that SQL server uses to store the database.

You will need to use SQL server to extract these. SQL Server Express is free and will do the job.

So, install SQL Server Express edition, and open the SQL Server Powershell. There execute sqlcmd -S <COMPUTERNAME>\SQLExpress (whilst logged in as administrator)

then issue the following command.

restore filelistonly from disk='c:\temp\mydbName-2009-09-29-v10.bak';

This will list the contents of the backup - what you need is the first fields that tell you the logical names - one will be the actual database and the other the log file.

RESTORE DATABASE mydbName FROM disk='c:\temp\mydbName-2009-09-29-v10.bak'
   MOVE 'mydbName' TO 'c:\temp\mydbName_data.mdf', 
   MOVE 'mydbName_log' TO 'c:\temp\mydbName_data.ldf';

At this point you have extracted the database - then install Microsoft's "Sql Web Data Administrator". together with this export tool and you will have an SQL script that contains the database.