Programs & Examples On #Nosql

NoSQL (sometimes expanded to "not only SQL") is a broad class of database management systems that differ from the classic model of the relational database management system (RDBMS) in some significant ways.

Cassandra port usage - how are the ports used?

For Apache Cassandra 2.0 you need to take into account the following TCP ports: (See EC2 security group configuration and Apache Cassandra FAQ)


  • 7199 JMX monitoring port
  • 1024 - 65355 Random port required by JMX. Starting with Java 7u4 a specific port can be specified using the property.
  • 7000 Inter-node cluster
  • 7001 SSL inter-node cluster
  • 9042 CQL Native Transport Port
  • 9160 Thrift

DataStax OpsCenter

  • 61620 opscenterd daemon
  • 61621 Agent
  • 8888 Website


A possible architecture with Cassandra + OpsCenter on EC2 could look like this: AWS EC2 with OpsCenter

MongoDB: How to update multiple documents with a single command?

Multi update was added recently, so is only available in the development releases (1.1.3). From the shell you do a multi update by passing true as the fourth argument to update(), where the the third argument is the upsert argument:

db.test.update({foo: "bar"}, {$set: {test: "success!"}}, false, true);

For versions of mongodb 2.2+ you need to set option multi true to update multiple documents at once.

db.test.update({foo: "bar"}, {$set: {test: "success!"}}, {multi: true})

For versions of mongodb 3.2+ you can also use new method updateMany() to update multiple documents at once, without the need of separate multi option.

db.test.updateMany({foo: "bar"}, {$set: {test: "success!"}})

Add new field to every document in a MongoDB collection

Since MongoDB version 3.2 you can use updateMany():

> db.yourCollection.updateMany({}, {$set:{"someField": "someValue"}})

NoSql vs Relational database

RDBMS focus more on relationship and NoSQL focus more on storage.

You can consider using NoSQL when your RDBMS reaches bottlenecks. NoSQL makes RDBMS more flexible.

SQL (MySQL) vs NoSQL (CouchDB)

Seems like only real solutions today revolve around scaling out or sharding. All modern databases (NoSQLs as well as NewSQLs) support horizontal scaling right out of the box, at the database layer, without the need for the application to have sharding code or something.

Unfortunately enough, for the trusted good-old MySQL, sharding is not provided "out of the box". ScaleBase (disclaimer: I work there) is a maker of a complete scale-out solution an "automatic sharding machine" if you like. ScaleBae analyzes your data and SQL stream, splits the data across DB nodes, and aggregates in runtime – so you won’t have to! And it's free download.

Don't get me wrong, NoSQLs are great, they're new, new is more choice and choice is always good!! But choosing NoSQL comes with a price, make sure you can pay it...

You can see here some more data about MySQL, NoSQL...:

Hope that helped.

When to use CouchDB over MongoDB and vice versa

Of C, A & P (Consistency, Availability & Partition tolerance) which 2 are more important to you? Quick reference, the Visual Guide To NoSQL Systems

  • MongodB : Consistency and Partition Tolerance
  • CouchDB : Availability and Partition Tolerance

A blog post, Cassandra vs MongoDB vs CouchDB vs Redis vs Riak vs HBase vs Membase vs Neo4j comparison has 'Best used' scenarios for each NoSQL database compared. Quoting the link,

  • MongoDB: If you need dynamic queries. If you prefer to define indexes, not map/reduce functions. If you need good performance on a big DB. If you wanted CouchDB, but your data changes too much, filling up disks.
  • CouchDB : For accumulating, occasionally changing data, on which pre-defined queries are to be run. Places where versioning is important.

A recent (Feb 2012) and more comprehensive comparison by Riyad Kalla,

  • MongoDB : Master-Slave Replication ONLY
  • CouchDB : Master-Master Replication

A blog post (Oct 2011) by someone who tried both, A MongoDB Guy Learns CouchDB commented on the CouchDB's paging being not as useful.

A dated (Jun 2009) benchmark by Kristina Chodorow (part of team behind MongoDB),

I'd go for MongoDB.

Hope it helps.

How to empty a redis database?

open your Redis cli and There two possible option that you could use:

FLUSHDB - Delete all the keys of the currently selected DB. FLUSHALL - Delete all the keys of all the existing databases, not just the currently selected one.

Is there a query language for JSON?

You could use linq.js.

This allows to use aggregations and selectings from a data set of objects, as other structures data.

var data = [{ x: 2, y: 0 }, { x: 3, y: 1 }, { x: 4, y: 1 }];_x000D_
// SUM(X) WHERE Y > 0     -> 7_x000D_
console.log(Enumerable.From(data).Where("$.y > 0").Sum("$.x"));_x000D_
// LIST(X) WHERE Y > 0    -> [3, 4]_x000D_
console.log(Enumerable.From(data).Where("$.y > 0").Select("$.x").ToArray());
<script src=""></script>

When to Redis? When to MongoDB?

Maybe this resource is useful helping decide between both. It also discusses several other NoSQL databases, and offers a short list of characteristics, along with a "what I would use it for" explanation for each of them.

What is Hash and Range Primary Key?

"Hash and Range Primary Key" means that a single row in DynamoDB has a unique primary key made up of both the hash and the range key. For example with a hash key of X and range key of Y, your primary key is effectively XY. You can also have multiple range keys for the same hash key but the combination must be unique, like XZ and XA. Let's use their examples for each type of table:

Hash Primary Key – The primary key is made of one attribute, a hash attribute. For example, a ProductCatalog table can have ProductID as its primary key. DynamoDB builds an unordered hash index on this primary key attribute.

This means that every row is keyed off of this value. Every row in DynamoDB will have a required, unique value for this attribute. Unordered hash index means what is says - the data is not ordered and you are not given any guarantees into how the data is stored. You won't be able to make queries on an unordered index such as Get me all rows that have a ProductID greater than X. You write and fetch items based on the hash key. For example, Get me the row from that table that has ProductID X. You are making a query against an unordered index so your gets against it are basically key-value lookups, are very fast, and use very little throughput.

Hash and Range Primary Key – The primary key is made of two attributes. The first attribute is the hash attribute and the second attribute is the range attribute. For example, the forum Thread table can have ForumName and Subject as its primary key, where ForumName is the hash attribute and Subject is the range attribute. DynamoDB builds an unordered hash index on the hash attribute and a sorted range index on the range attribute.

This means that every row's primary key is the combination of the hash and range key. You can make direct gets on single rows if you have both the hash and range key, or you can make a query against the sorted range index. For example, get Get me all rows from the table with Hash key X that have range keys greater than Y, or other queries to that affect. They have better performance and less capacity usage compared to Scans and Queries against fields that are not indexed. From their documentation:

Query results are always sorted by the range key. If the data type of the range key is Number, the results are returned in numeric order; otherwise, the results are returned in order of ASCII character code values. By default, the sort order is ascending. To reverse the order, set the ScanIndexForward parameter to false

I probably missed some things as I typed this out and I only scratched the surface. There are a lot more aspects to take into consideration when working with DynamoDB tables (throughput, consistency, capacity, other indices, key distribution, etc.). You should take a look at the sample tables and data page for examples.

How do you query for "is not null" in Mongo?

In pymongo you can use:

db.mycollection.find({"IMAGE URL":{"$ne":None}});

Because pymongo represents mongo "null" as python "None".

Delete all nodes and relationships in neo4j 1.8

if the name of node is for example : abcd then below query will work :

MATCH (n:abcd)

This will only delete the node with label "abcd" and all its relation-ships.

NoSQL Use Case Scenarios or WHEN to use NoSQL

It really is an "it depends" kinda question. Some general points:

  • NoSQL is typically good for unstructured/"schemaless" data - usually, you don't need to explicitly define your schema up front and can just include new fields without any ceremony
  • NoSQL typically favours a denormalised schema due to no support for JOINs per the RDBMS world. So you would usually have a flattened, denormalized representation of your data.
  • Using NoSQL doesn't mean you could lose data. Different DBs have different strategies. e.g. MongoDB - you can essentially choose what level to trade off performance vs potential for data loss - best performance = greater scope for data loss.
  • It's often very easy to scale out NoSQL solutions. Adding more nodes to replicate data to is one way to a) offer more scalability and b) offer more protection against data loss if one node goes down. But again, depends on the NoSQL DB/configuration. NoSQL does not necessarily mean "data loss" like you infer.
  • IMHO, complex/dynamic queries/reporting are best served from an RDBMS. Often the query functionality for a NoSQL DB is limited.
  • It doesn't have to be a 1 or the other choice. My experience has been using RDBMS in conjunction with NoSQL for certain use cases.
  • NoSQL DBs often lack the ability to perform atomic operations across multiple "tables".

You really need to look at and understand what the various types of NoSQL stores are, and how they go about providing scalability/data security etc. It's difficult to give an across-the-board answer as they really are all different and tackle things differently.

For MongoDb as an example, check out their Use Cases to see what they suggest as being "well suited" and "less well suited" uses of MongoDb.

What is the recommended way to delete a large number of items from DynamoDB?

If you want to delete items after some time, e.g. after a month, just use Time To Live option. It will not count write units.

In your case, I would add ttl when logs expire and leave those after a user is deleted. TTL would make sure logs are removed eventually.

When Time To Live is enabled on a table, a background job checks the TTL attribute of items to see if they are expired.

DynamoDB typically deletes expired items within 48 hours of expiration. The exact duration within which an item truly gets deleted after expiration is specific to the nature of the workload and the size of the table. Items that have expired and not been deleted will still show up in reads, queries, and scans. These items can still be updated and successful updates to change or remove the expiration attribute will be honored.

Mongodb: Failed to connect to, reason: errno:10061

first you run the command mongod and check weather the port 27017 has started or not if yes then hit the command mongo....and database will start.

Difference between scaling horizontally and vertically for databases

There is an additional architecture that wasn't mentioned - SQL-based database services that enable horizontal scaling without the complexity of manual sharding. These services do the sharding in the background, so they enable you to run a traditional SQL database and scale out like you would with NoSQL engines like MongoDB or CouchDB. Two services I am familiar with are EnterpriseDB for PostgreSQL and Xeround for MySQL. I saw an in-depth post by Xeround which explains why scale-out on SQL databases is difficult and how they do it differently - treat this with a grain of salt as it is a vendor post. Also check out Wikipedia's Cloud Database entry, there is a nice explanation of SQL vs. NoSQL and service vs. self-hosted, a list of vendors and scaling options for each combination. ;)

Firestore Getting documents id from collection

Can get ID before add documents in database:

var idBefore =  this.afs.createId();

Explanation of JSONB introduced by PostgreSQL


The short answer is:

  • If you are doing a lot of JSON manipulation inside PostgreSQL, such as sorting, slicing, splicing, etc., you should use JSONB for speed reasons.
  • If you need indexed lookups for arbitrary key searches on JSON, then you should use JSONB.
  • If you are doing neither of the above, you should probably use JSON.
  • If you need to preserve key ordering, whitespace, and duplicate keys, you should use JSON.

For a longer answer, you'll need to wait for me to do a full "HowTo" writeup closer to the 9.4 release.

How can I run MongoDB as a Windows service?

I'm on version 2.4.9 and using a config file. The service wouldn't start until I surrounded the equals sign in the config file with spaces:

dbpath = D:\Mongo data
logpath = C:\mongodb\logs\mongo.log 
logappend = true

Originally I had:


I also discovered that when installing the service that you have to use an absolute path for the config file eg:

c:\mongodb\bin\>mongodb.exe C:\mongodb\bin\mongod.conf --install

Don't be tempted to put inverted commas around a dbpath with spaces. The service will appear to start when you execute net start MongoDB but it will terminate. Check the log files for confirmation that the service has really started.

DynamoDB vs MongoDB NoSQL

For quick overview comparisons, I really like this website, that has many comparison pages, eg AWS DynamoDB vs MongoDB;

Is mongodb running?

Probably because I didn't shut down my dev server properly or a similar reason. To fix it, remove the lock and start the server with: sudo rm /var/lib/mongodb/mongod.lock ; sudo start mongodb

Foreign keys in mongo?

The purpose of ForeignKey is to prevent the creation of data if the field value does not match its ForeignKey. To accomplish this in MongoDB, we use Schema middlewares that ensure the data consistency.

Please have a look at the documentation.

Querying DynamoDB by date

Approach I followed to solve this problem is by created a Global Secondary Index as below. Not sure if this is the best approach but hopefully if it is useful to someone.

Hash Key                 | Range Key
Date value of CreatedAt  | CreatedAt

Limitation imposed on the HTTP API user to specify the number of days to retrieve data, defaulted to 24 hr.

This way, I can always specify the HashKey as Current date's day and RangeKey can use > and < operators while retrieving. This way the data is also spread across multiple shards.

Explanation of BASE terminology

It could just be because ACID is one set of properties that substances show( in Chemistry) and BASE is a complement set of them.So it could be just to show the contrast between the two that the acronym was made up and then 'Basically Available Soft State Eventual Consistency' was decided as it's full-form.

OS X Terminal shortcut: Jump to beginning/end of line

in iterm2

fn + leftArraw or fn + rightArrow

this worked for me

Cannot find the object because it does not exist or you do not have permissions. Error in SQL Server

I found a reason why this would happen. The user had the appropriate permissions, but the stored procedure included a TRUNCATE statement:


Since TRUNCATE deletes items without logging, you (apparently) need elevated permissions to execute a stored procedure that contains it. We changed the statement to:


...and the error went away!

How to change the color of winform DataGridview header?

The way to do this is to set the EnableHeadersVisualStyles flag for the data grid view to False, and set the background colour via the ColumnHeadersDefaultCellStyle.BackColor property. For example, to set the background colour to blue, use the following (or set in the designer if you prefer):

_dataGridView.ColumnHeadersDefaultCellStyle.BackColor = Color.Blue;
_dataGridView.EnableHeadersVisualStyles = false;

If you do not set the EnableHeadersVisualStyles flag to False, then the changes you make to the style of the header will not take effect, as the grid will use the style from the current users default theme. The MSDN documentation for this property is here.

CSS Positioning Elements Next to each other

If you want them to be displayed side by side, why is sideContent the child of mainContent? make them siblings then use:

float:left; display:inline; width: 49%;

on both of them.

#mainContent, #sideContent {float:left; display:inline; width: 49%;}

C error: undefined reference to function, but it IS defined

Add the "extern" keyword to the function definitions in point.h

What to do on TransactionTooLargeException

You have clear your old InstanceState from onSaveInstanceState method, and it will work well. I am using FragmentStatePagerAdapter for my viewpager so I keep below Override method into my parent activity for clear InstanceState.

protected void onSaveInstanceState(Bundle InstanceState) {

I found this solution from here android.os.TransactionTooLargeException on Nougat

Error:Conflict with dependency ''

METHOD 1: I deleted the androidTestCompile on espresso-core line which was automatically included in a new project. Then my Android Studio compiles clean.

The androidTestCompile is in "build.gradle (Module:app)":

dependencies {
    androidTestCompile('', {
        exclude group: '', module: 'support-annotations'

I don't know whether this deletion will have any problem down the road, but it surely works for my current project now.

METHOD 2: Adding an exclude on findbugs works too:

dependencies {
    androidTestCompile('', {
        exclude group: '', module: 'support-annotations'
        exclude group: ''

METHOD 3: Forcing compiling with a specific version:

(In the following I force it to compile with the higher version.)

dependencies {
    androidTestCompile ''

Conditional replacement of values in a data.frame

Here is one approach. ifelse is vectorized and it checks all rows for zero values of b and replaces est with (a - 5)/2.53 if that is the case.

df <- transform(df, est = ifelse(b == 0, (a - 5)/2.53, est))

Windows command prompt log to a file

You can redirect the output of a cmd prompt to a file using > or >> to append to a file.


echo Hello World >C:\output.txt
echo Hello again! >>C:\output.txt


mybatchfile.bat >C:\output.txt

Note that using > will automatically overwrite the file if it already exists.

You also have the option of redirecting stdin, stdout and stderr.

See here for a complete list of options.

How to get all child inputs of a div element (jQuery)

here is my approach:

You can use it in other event.

var id;_x000D_
$("#panel :input").each(function(e){ _x000D_
  id =;_x000D_
  // show id _x000D_
  // show input value _x000D_
  // disable input if you want_x000D_
  //$("#"+id).prop('disabled', true);_x000D_
<script src=""></script>_x000D_
<div id="panel">_x000D_
       <td><input id="Search_NazovProjektu" type="text" value="Naz Val" /></td>_x000D_
       <td><input id="Search_Popis" type="text" value="Po Val" /></td>_x000D_

How to copy a dictionary and only edit the copy

This confused me too, initially, because I was coming from a C background.

In C, a variable is a location in memory with a defined type. Assigning to a variable copies the data into the variable's memory location.

But in Python, variables act more like pointers to objects. So assigning one variable to another doesn't make a copy, it just makes that variable name point to the same object.

Java, how to compare Strings with String Arrays

If I understand your question correctly, it appears you want to know the following:

How do I check if my String array contains usercode, the String that was just inputted?

See here for a similar question. It quotes solutions that have been pointed out by previous answers. I hope this helps.

Listing files in a directory matching a pattern in Java

The following code will create a list of files based on the accept method of the FileNameFilter.

List<File> list = Arrays.asList(dir.listFiles(new FilenameFilter(){
        public boolean accept(File dir, String name) {
            return name.endsWith(".exe"); // or something else

bind/unbind service example (android)

You can try using this code:

protected ServiceConnection mServerConn = new ServiceConnection() {
    public void onServiceConnected(ComponentName name, IBinder binder) {
        Log.d(LOG_TAG, "onServiceConnected");

    public void onServiceDisconnected(ComponentName name) {
        Log.d(LOG_TAG, "onServiceDisconnected");

public void start() {
    // mContext is defined upper in code, I think it is not necessary to explain what is it 
    mContext.bindService(intent, mServerConn, Context.BIND_AUTO_CREATE);

public void stop() {
    mContext.stopService(new Intent(mContext, ServiceRemote.class));

How do I vertically align text in a paragraph?

If you use Bootstrap, try to assign margin-bottom 0 to the paragraph and after assign the property align-items-center to container, for example, like this:

<div class="row align-items-center">
     <p class="col-sm-1 mb-0">

Bootstrap by default assign a calculate margin bottom, so mb-0 disabled this.

I hope it helps

__init__() got an unexpected keyword argument 'user'

LivingRoom.objects.create() calls LivingRoom.__init__() - as you might have noticed if you had read the traceback - passing it the same arguments. To make a long story short, a Django models.Model subclass's initializer is best left alone, or should accept *args and **kwargs matching the model's meta fields. The correct way to provide default values for fields is in the field constructor using the default keyword as explained in the FineManual.

How to check if another instance of the application is running

You can try this

Process[] processes = Process.GetProcessesByName("processname");
foreach (Process p in processes)
    IntPtr pFoundWindow = p.MainWindowHandle;
    // Do something with the handle...

How to shutdown my Jenkins safely?

Immediately shuts down Jenkins server.

In Windows CMD.exe, Go to folder where jenkins-cli.jar file is located.

C:\Program Files (x86)\Jenkins\war\WEB-INF

Use Command to Safely Shutdown

java -jar jenkins-cli.jar -s http://localhost:8080 safe-shutdown --username "YourUsername" 
--password "YourPassword"

The full list of commands is available at http://localhost:8080/cli

Credits to Francisco post for cli commands.



Hope helps someone.

initialize a const array in a class initializer in C++

std::vector uses the heap. Geez, what a waste that would be just for the sake of a const sanity-check. The point of std::vector is dynamic growth at run-time, not any old syntax checking that should be done at compile-time. If you're not going to grow then create a class to wrap a normal array.

#include <stdio.h>

template <class Type, size_t MaxLength>
class ConstFixedSizeArrayFiller {
    size_t length;

    ConstFixedSizeArrayFiller() : length(0) {

    virtual ~ConstFixedSizeArrayFiller() {

    virtual void Fill(Type *array) = 0;

    void add_element(Type *array, const Type & element)
        if(length >= MaxLength) {
            // todo: throw more appropriate out-of-bounds exception
            throw 0;
        array[length] = element;

template <class Type, size_t Length>
class ConstFixedSizeArray {
    Type array[Length];

    explicit ConstFixedSizeArray(
        ConstFixedSizeArrayFiller<Type, Length> & filler
    ) {

    const Type *Array() const {
        return array;

    size_t ArrayLength() const {
        return Length;

class a {
    class b_filler : public ConstFixedSizeArrayFiller<int, 2> {
        virtual ~b_filler() {

        virtual void Fill(int *array) {
            add_element(array, 87);
            add_element(array, 96);

    const ConstFixedSizeArray<int, 2> b;

    a(void) : b(b_filler()) {

    void print_items() {
        size_t i;
        for(i = 0; i < b.ArrayLength(); i++)
            printf("%d\n", b.Array()[i]);

int main()
    a x;
    return 0;

ConstFixedSizeArrayFiller and ConstFixedSizeArray are reusable.

The first allows run-time bounds checking while initializing the array (same as a vector might), which can later become const after this initialization.

The second allows the array to be allocated inside another object, which could be on the heap or simply the stack if that's where the object is. There's no waste of time allocating from the heap. It also performs compile-time const checking on the array.

b_filler is a tiny private class to provide the initialization values. The size of the array is checked at compile-time with the template arguments, so there's no chance of going out of bounds.

I'm sure there are more exotic ways to modify this. This is an initial stab. I think you can pretty much make up for any of the compiler's shortcoming with classes.

How can I get a process handle by its name in C++?

The following code can be used:

DWORD FindProcessId(const std::wstring& processName)
    PROCESSENTRY32 processInfo;
    processInfo.dwSize = sizeof(processInfo);

    HANDLE processesSnapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, NULL);
    if (processesSnapshot == INVALID_HANDLE_VALUE) {
        return 0;

    Process32First(processesSnapshot, &processInfo);
    if (!
        return processInfo.th32ProcessID;

    while (Process32Next(processesSnapshot, &processInfo))
        if (!
            return processInfo.th32ProcessID;

    return 0;


auto processId = FindProcessId(L"blabla.exe");

Getting a handle should be obvious, just call OpenProcess() or similar on it.

"Insufficient Storage Available" even there is lot of free space in device memory

If you have root, delete all of the folders on the path:


And then restart your device.

I had this issue many times, and this fix worked for me each time. It even has an XDA thread.

I write all folders, because if there is a problem with one app, there is a good chance you have this issue with other apps too. Plus, it's annoying to find just the folders of the problematic app/s .

Best way to integrate Python and JavaScript?

If your just interested in sharing complex data types between javascript and python, check out jsonpickle. It wraps the standard Python JSON libraries, but has some smarts in serializing and deserializing Python classes and other data types.

Quite a few Google App Engine projects have used this library. Joose and FirePython both incorporate jsonpickle.

Comparing two branches in Git?

git diff branch_1..branch_2

That will produce the diff between the tips of the two branches. If you'd prefer to find the diff from their common ancestor to test, you can use three dots instead of two:

git diff branch_1...branch_2

Prevent flicker on webkit-transition of webkit-transform

I found that applying the -webkit-backface-visibility: hidden; to the translating element and -webkit-transform: translate3d(0,0,0); to all its children, the flicker then disappears

How do I check if a string contains a specific word?

I think that a good idea is to use mb_stpos:

$haystack = 'How are you?';
$needle = 'are';

if (mb_strpos($haystack, $needle) !== false) {

    echo 'true';

Because this solution is case sensitive and safe for all Unicode characters.

But you can also do it like this (sauch response was not yet):

if (count(explode($needle, $haystack)) > 1) {

    echo 'true';

This solution is also case sensitive and safe for Unicode characters.

In addition you do not use the negation in the expression, which increases the readability of the code.

Here is other solution using function:

function isContainsStr($haystack, $needle) {

    return count(explode($needle, $haystack)) > 1;

if (isContainsStr($haystack, $needle)) {

    echo 'true';

How to cherry pick a range of commits and merge into another branch?

As of git v1.7.2 cherry pick can accept a range of commits:

git cherry-pick learned to pick a range of commits (e.g. cherry-pick A..B and cherry-pick --stdin), so did git revert; these do not support the nicer sequencing control rebase [-i] has, though.

How to get all possible combinations of a list’s elements?

This one-liner gives you all the combinations (between 0 and n items if the original list/set contains n distinct elements) and uses the native method itertools.combinations:

Python 2

from itertools import combinations

input = ['a', 'b', 'c', 'd']

output = sum([map(list, combinations(input, i)) for i in range(len(input) + 1)], [])

Python 3

from itertools import combinations

input = ['a', 'b', 'c', 'd']

output = sum([list(map(list, combinations(input, i))) for i in range(len(input) + 1)], [])

The output will be:

 ['a', 'b'],
 ['a', 'c'],
 ['a', 'd'],
 ['b', 'c'],
 ['b', 'd'],
 ['c', 'd'],
 ['a', 'b', 'c'],
 ['a', 'b', 'd'],
 ['a', 'c', 'd'],
 ['b', 'c', 'd'],
 ['a', 'b', 'c', 'd']]

Try it online:

MySQL Alter Table Add Field Before or After a field already present

$query = "ALTER TABLE `" . $table_prefix . "posts_to_bookmark` 
          ADD COLUMN `ping_status` INT(1) NOT NULL 

I believe you need to have ADD COLUMN and use AFTER, not BEFORE.

In case you want to place column at the beginning of a table, use the FIRST statement:

$query = "ALTER TABLE `" . $table_prefix . "posts_to_bookmark`
          ADD COLUMN `ping_status` INT(1) NOT NULL 

How do I upload a file with metadata using a REST web service?

One way to approach the problem is to make the upload a two phase process. First, you would upload the file itself using a POST, where the server returns some identifier back to the client (an identifier might be the SHA1 of the file contents). Then, a second request associates the metadata with the file data:

    "Name": "Test",
    "Latitude": 12.59817,
    "Longitude": 52.12873,
    "ContentID": "7a788f56fa49ae0ba5ebde780efe4d6a89b5db47"

Including the file data base64 encoded into the JSON request itself will increase the size of the data transferred by 33%. This may or may not be important depending on the overall size of the file.

Another approach might be to use a POST of the raw file data, but include any metadata in the HTTP request header. However, this falls a bit outside basic REST operations and may be more awkward for some HTTP client libraries.

Illegal access: this web application instance has been stopped already

Problem solved after restarting the tomcat and apache, the tomcat was caching older version of the app.

Set background colour of cell to RGB value of data in cell

You can use VBA - something like

Range("A1:A6").Interior.Color = RGB(127,187,199)

Just pass in the cell value.

error: strcpy was not declared in this scope

This error sometimes occurs in a situation like this:

#ifndef NAN
#include <stdlib.h>
#define NAN (strtod("NAN",NULL))

static void init_random(uint32_t initseed=0)
    if (initseed==0)
        struct timeval tv;
        gettimeofday(&tv, NULL);
        seed=(uint32_t) (4223517*getpid()*tv.tv_sec*tv.tv_usec);
#if !defined(CYGWIN) && !defined(__INTERIX)
    //SG_SPRINT("initializing random number generator with %d (seed size %d)\n", seed, RNG_SEED_SIZE)
    initstate(seed, CMath::rand_state, RNG_SEED_SIZE);

If the following code lines not run in the run-time:

#ifndef NAN
#include <stdlib.h>
#define NAN (strtod("NAN",NULL))

you will face with an error in your code like something as follows; because initstate is placed in the stdlib.h file and it's not included:

In file included from ../../shogun/features/SubsetStack.h:14:0, 
                 from ../../shogun/features/Features.h:21, 
                 from ../../shogun/ui/SGInterface.h:7, 
                 from MatlabInterface.h:15, 
                 from matlabInterface.cpp:7: 
../../shogun/mathematics/Math.h: In static member function 'static void shogun::CMath::init_random(uint32_t)': 
../../shogun/mathematics/Math.h:459:52: error: 'initstate' was not declared in this scope

Decrypt password created with htpasswd

.htpasswd entries are HASHES. They are not encrypted passwords. Hashes are designed not to be decryptable. Hence there is no way (unless you bruteforce for a loooong time) to get the password from the .htpasswd file.

What you need to do is apply the same hash algorithm to the password provided to you and compare it to the hash in the .htpasswd file. If the user and hash are the same then you're a go.

White space showing up on right side of page when background image should extend full length of page

Debug your CSS for Ghost CSS Elements.

Use this bookmark to debug your CSS:

Or add the CSS directly yourself:

* {
  background: #000 !important;
  color: #0f0 !important;
  outline: solid #f00 1px !important;

In my case a Facebook Like Button caused the problem.

iOS UIImagePickerController result image orientation after upload

If I understand, what you want to do is disregard the orientation of the UIImage? If so then you could do this:-

//image is your original image
image = [UIImage imageWithCGImage:[image CGImage]
                             scale:[image scale]
                       orientation: UIImageOrientationUp];

or in Swift :-

image = UIImage(CGImage: image.CGImage!, scale: image.scale, orientation:.Up)

It solved my cropping issue.. Hope, this is what you're looking for..

How to put a tooltip on a user-defined function

Unfortunately there is no way to add Tooltips for UDF Arguments.
To extend Remou's reply you can find a fuller but more complex approach to descriptions for the Function Wizard at

MySQL date formats - difficulty Inserting a date

The date format for mysql insert query is YYYY-MM-DD


INSERT INTO table_name (date_column) VALUE ('YYYY-MM-DD');

How to set environment variables from within package.json?

Try this on Windows by replacing YOURENV:

     "scripts": {
       "help": "set NODE_ENV=YOURENV && tagove help",
       "start": "set NODE_ENV=YOURENV && tagove start"

How to call function that takes an argument in a Django template?

I'm passing to Django's template a function, which returns me some records

Why don't you pass to Django template the variable storing function's return value, instead of the function?

I've tried to set fuction's return value to a variable and iterate over variable, but there seems to be no way to set variable in Django template.

You should set variables in Django views instead of templates, and then pass them to the template.

How do I get a human-readable file size in bytes abbreviation using .NET?

This is not the most efficient way to do it, but it's easier to read if you are not familiar with log maths, and should be fast enough for most scenarios.

string[] sizes = { "B", "KB", "MB", "GB", "TB" };
double len = new FileInfo(filename).Length;
int order = 0;
while (len >= 1024 && order < sizes.Length - 1) {
    len = len/1024;

// Adjust the format string to your preferences. For example "{0:0.#}{1}" would
// show a single decimal place, and no space.
string result = String.Format("{0:0.##} {1}", len, sizes[order]);

Cross browser method to fit a child div to its parent's width

If you put position:relative; on the outer element, the inner element will place itself according to this one. Then a width:auto; on the inner element will be the same as the width of the outer.

How to add "active" class to wp_nav_menu() current menu item (simple way)

To also highlight the menu item when one of the child pages is active, also check for the other class (current-page-ancestor) like below:

add_filter('nav_menu_css_class' , 'special_nav_class' , 10 , 2);

function special_nav_class ($classes, $item) {
    if (in_array('current-page-ancestor', $classes) || in_array('current-menu-item', $classes) ){
        $classes[] = 'active ';
    return $classes;

Setting the MySQL root user password on OS X

None of the previous comments solve the issue on my Mac. I used the commands below and it worked.

$ brew services stop mysql
$ pkill mysqld
$ rm -rf /usr/local/var/mysql/ # NOTE: this will delete your existing database!!!
$ brew postinstall mysql
$ brew services restart mysql
$ mysql -u root

How do I Alter Table Column datatype on more than 1 column?

ALTER TABLE can do multiple table alterations in one statement, but MODIFY COLUMN can only work on one column at a time, so you need to specify MODIFY COLUMN for each column you want to change:

ALTER TABLE webstore.Store

Also, note this warning from the manual:

When you use CHANGE or MODIFY, column_definition must include the data type and all attributes that should apply to the new column, other than index attributes such as PRIMARY KEY or UNIQUE. Attributes present in the original definition but not specified for the new definition are not carried forward.

Getting IP address of client

I use the following static helper method to retrieve the IP of a client:

public static String getClientIpAddr(HttpServletRequest request) {  
    String ip = request.getHeader("X-Forwarded-For");  
    if (ip == null || ip.length() == 0 || ip.equalsIgnoreCase("unknown")) {  
        ip = request.getHeader("Proxy-Client-IP");  
    if (ip == null || ip.length() == 0 || ip.equalsIgnoreCase("unknown")) {  
        ip = request.getHeader("WL-Proxy-Client-IP");  
    if (ip == null || ip.length() == 0 || ip.equalsIgnoreCase("unknown")) {  
        ip = request.getHeader("HTTP_X_FORWARDED_FOR");  
    if (ip == null || ip.length() == 0 || ip.equalsIgnoreCase("unknown")) {  
        ip = request.getHeader("HTTP_X_FORWARDED");  
    if (ip == null || ip.length() == 0 || ip.equalsIgnoreCase("unknown")) {  
        ip = request.getHeader("HTTP_X_CLUSTER_CLIENT_IP");  
    if (ip == null || ip.length() == 0 || ip.equalsIgnoreCase("unknown")) {  
        ip = request.getHeader("HTTP_CLIENT_IP");  
    if (ip == null || ip.length() == 0 || ip.equalsIgnoreCase("unknown")) {  
        ip = request.getHeader("HTTP_FORWARDED_FOR");  
    if (ip == null || ip.length() == 0 || ip.equalsIgnoreCase("unknown")) {  
        ip = request.getHeader("HTTP_FORWARDED");  
    if (ip == null || ip.length() == 0 || ip.equalsIgnoreCase("unknown")) {  
        ip = request.getHeader("HTTP_VIA");  
    if (ip == null || ip.length() == 0 || ip.equalsIgnoreCase("unknown")) {  
        ip = request.getHeader("REMOTE_ADDR");  
    if (ip == null || ip.length() == 0 || ip.equalsIgnoreCase("unknown")) {  
        ip = request.getRemoteAddr();  
    return ip;  

Maven build debug in Eclipse

Easiest way I find is to:

  1. Right click project

  2. Debug as -> Maven build ...

  3. In the goals field put -Dmaven.surefire.debug test

  4. In the parameters put a new parameter called forkCount with a value of 0 (previously was forkMode=never but it is deprecated and doesn't work anymore)

Set your breakpoints down and run this configuration and it should hit the breakpoint.

What causes the error "undefined reference to (some function)"?

It's a linker error. ld is the linker, so if you get an error message ending with "ld returned 1 exit status", that tells you that it's a linker error.

The error message tells you that none of the object files you're linking against contains a definition for avergecolumns. The reason for that is that the function you've defined is called averagecolumns (in other words: you misspelled the function name when calling the function (and presumably in the header file as well - otherwise you'd have gotten a different error at compile time)).

Getting a list of all subdirectories in the current directory

Listing Out only directories

print("\nWe are listing out only the directories in current directory -")
directories_in_curdir = filter(os.path.isdir, os.listdir(os.curdir))

Listing Out only files in current directory

files = filter(os.path.isfile, os.listdir(os.curdir))
print("\nThe following are the list of all files in the current directory -")

How to break out of nested loops?

int i = 0, j= 0;

for(i;i< 1000; i++){    
    for(j; j< 1000; j++){
            i = j = 1001;

Will break both the loops.

How to start Fragment from an Activity

Firstly, you start Activities and Services with an intent, you start fragments with fragment transactions. Secondly, your transaction isnt doing anything. Change it to something like:

FragmentTransaction transaction = getFragmentManager();
        .replace(R.layout.container, newFragment) //<---replace a view in your layout (id: container) with the newFragment 

How to show x and y axes in a MATLAB graph?

@Martijn your order of function calls is slightly off. Try this instead:

y = x.^3;
plot(x,y), hold on
plot([-3 3], [0 0], 'k:')
hold off

Why does Maven have such a bad rep?

Some of my pet peeves with Maven:

  • The XML definition is super clumsy and verbose. Have they never heard of attributes?

  • In its default configuration, it always scours the 'net on every operation. Regardless of whether this is useful for anything, it looks extremely silly to need Internet access for "clean".

  • Again in the default, if I'm not careful to specify exact version numbers, it will pull the very latest updates off the 'net, regardless of whether these newest versions introduce dependency errors. In other words, you're placed at the mercy of other peoples' dependency management.

  • The solution to all this network access is to turn it off by adding the -o option. But you have to remember to turn it off if you really want to do dependency updating!

  • Another solution is to install your own "source control" server for dependencies. Surprise: Most projects already have source control, only that works with no additional setup!

  • Maven builds are incredibly slow. Fiddling with network updates alleviates this, but Maven builds are still slow. And horribly verbose.

  • The Maven plugin (M2Eclipse) integrates most poorly with Eclipse. Eclipse integrates reasonably smoothly with version control software and with Ant. Maven integration is very clunky and ugly by comparison. Did I mention slow?

  • Maven continues to be buggy. Error messages are unhelpful. Too many developers are suffering from this.

how to execute php code within javascript

Any server side stuff such as php declaration must get evaluated in the host file (file with a .php extension) inside the script tags such as below

<script type="text/javascript">
    var1 = "<?php echo 'Hello';?>";

Then in the .js file, you can use the variable


If you try to evaluate php declaration in the .js file, it will NOT work

How to find MySQL process list and to kill those processes?

Here is the solution:

  1. Login to DB;
  2. Run a command show full processlist;to get the process id with status and query itself which causes the database hanging;
  3. Select the process id and run a command KILL <pid>; to kill that process.

Sometimes it is not enough to kill each process manually. So, for that we've to go with some trick:

  1. Login to MySQL;
  2. Run a query Select concat('KILL ',id,';') from information_schema.processlist where user='user'; to print all processes with KILL command;
  3. Copy the query result, paste and remove a pipe | sign, copy and paste all again into the query console. HIT ENTER. BooM it's done.

rails generate model

For me what happened was that I generated the app with rails new rails new chapter_2 but the RVM --default had rails 4.0.2 gem, but my chapter_2 project use a new gemset with rails 3.2.16.

So when I ran

rails generate scaffold User name:string email:string

the console showed

   rails new APP_PATH [options]

So I fixed the RVM and the gemset with the rails 3.2.16 gem , and then generated the app again then I executed

 rails generate scaffold User name:string email:string

and it worked

All combinations of a list of lists

Numpy can do it:

 >>> import numpy
 >>> a = [[1,2,3],[4,5,6],[7,8,9,10]]
 >>> [list(x) for x in numpy.array(numpy.meshgrid(*a)).T.reshape(-1,len(a))]
[[ 1, 4, 7], [1, 5, 7], [1, 6, 7], ....]

LINQ with groupby and count

userInfos.GroupBy(userInfo => userInfo.metric)
        .OrderBy(group => group.Key)
        .Select(group => Tuple.Create(group.Key, group.Count()));

ln (Natural Log) in Python

Here is the correct implementation using numpy (np.log() is the natural logarithm)

import numpy as np
p = 100
r = 0.06 / 12
FV = 4000

n = np.log(1 + FV * r/ p) / np.log(1 + r)

print ("Number of periods = " + str(n))


Number of periods = 36.55539635919235

How to make a smaller RatingBar?

                    style = "?android:attr/ratingBarStyleSmall"

// if you want to style 

 <style name="RatingBar" parent="Theme.AppCompat">
        <item name="colorControlNormal">@color/colorPrimary</item>
        <item name="colorControlActivated">@color/colorAccent</item>

// add these line for small rating bar

style = "?android:attr/ratingBarStyleSmall"

Relative URLs in WordPress

I agree with Rup. I guess the main reason is to avoid confusion on relative paths. I think wordpress can work from scratch with relative paths but the problem might come when using multiple plugins, how the theme is configured etc.

I've once used this plugin for relative paths, when working on testing servers:

Root Relative URLs
Converts all URLs to root-relative URLs for hosting the same site on multiple IPs, easier production migration and better mobile device testing.

Accessing JSON object keys having spaces

The way to do this is via the bracket notation.

var test = {_x000D_
    "id": "109",_x000D_
    "No. of interfaces": "4"_x000D_
alert(test["No. of interfaces"]);

For more info read out here:

JavaScript to scroll long page to DIV

old question, but if anyone finds this through google (as I did) and who does not want to use anchors or jquery; there's a builtin javascriptfunction to 'jump' to an element;


and what's even better; according to the great compatibility-tables on quirksmode, this is supported by all major browsers!

How to get max value of a column using Entity Framework?

If the list is empty I get an exception. This solution will take into account this issue:

int maxAge = context.Persons.Select(p => p.Age).DefaultIfEmpty(0).Max();

Should I set max pool size in database connection string? What happens if I don't?

Currently your application support 100 connections in pool. Here is what conn string will look like if you want to increase it to 200:

public static string srConnectionString = 
                "server=localhost;database=mydb;uid=sa;pwd=mypw;Max Pool Size=200;";

You can investigate how many connections with database your application use, by executing sp_who procedure in your database. In most cases default connection pool size will be enough.

Javascript to Select Multiple options

This type of thing should be done server-side, so as to limit the amount of resources used on the client for such trivial tasks. That being said, if you were to do it on the front-end, I would encourage you to consider using something like underscore.js to keep the code clean and concise:

var values = ["Red", "Green"],
    colors = document.getElementById("colors");

_.each(colors.options, function (option) {
    option.selected = ~_.indexOf(values, option.text);

If you're using jQuery, it could be even more terse:

var values = ["Red", "Green"];

$("#colors option").prop("selected", function () {
    return ~$.inArray(this.text, values);

If you were to do this without a tool like underscore.js or jQuery, you would have a bit more to write, and may find it to be a bit more complicated:

var color, i, j,
    values = ["Red", "Green"],
    options = document.getElementById("colors").options;

for ( i = 0; i < values.length; i++ ) {
    for ( j = 0, color = values[i]; j < options.length; j++ ) {
        options[j].selected = options[j].selected || color === options[j].text;

Removing elements with in JavaScript

You must note however that the Array.filter is not supported in all browser so, you must to prototyped:

//This prototype is provided by the Mozilla foundation and
//is distributed under the MIT license.

if (!Array.prototype.filter)
    Array.prototype.filter = function(fun /*, thisp*/)
        var len = this.length;

        if (typeof fun != "function")
            throw new TypeError();

        var res = new Array();
        var thisp = arguments[1];

        for (var i = 0; i < len; i++)
            if (i in this)
                var val = this[i]; // in case fun mutates this

                if (, val, i, this))

        return res;

And doing so, you can prototype any method you may need.

CSS Change List Item Background Color with Class

This is an issue of selector specificity. (The selector .selected is less specific than ul.nav li.)

To fix, use as much specificity in the overriding rule as in the original:

ul.nav li {
ul.nav li.selected {

You might also consider nixing the ul, unless there will be other .navs. So:

.nav li {
.nav li.selected {

That's a bit cleaner, less typing, and fewer bits.

How do I import a sql data file into SQL Server?

If you are talking about an actual database (an mdf file) you would Attach it

.sql files are typically run using SQL Server Management Studio. They are basically saved SQL statements, so could be anything. You don't "import" them. More precisely, you "execute" them. Even though the script may indeed insert data.

Also, to expand on Jamie F's answer, don't run a SQL file against your database unless you know what it is doing. SQL scripts can be as dangerous as unchecked exe's

Validate email with a regex in jQuery

Email: {
                      group: '.col-sm-3',
                      enabled: false,
                      validators: {
                          //emailAddress: {
                          //    message: 'Email not Valid'
                          regexp: {
                              regexp: '^[^@\\s]+@([^@\\s]+\\.)+[^@\\s]+$',
                              message: 'Email not Valid'

How to use BigInteger?

Yes it's Immutable


so the method add() of BigInteger class does not add new BigIntger value to its own value ,but creates and returns a new BigInteger reference without changing the current BigInteger and this is what done even in the case of Strings

How to make full screen background in a web page

A quick search for keywords background generator shows this CSS3 produced background pattern that's dynamically created.

By keeping the image small and repeatable, you won't have problems with it loading on mobile devices and the small image file-size takes care of memory concerns.

Here's the markup for the head section:

<style type="text/css">

    body {
      width: 100%;
      height: 100%;


If your going to use an image of something that should preserve aspect ratio, such as people or objects, then you don't want 100% for width and height since that will stretch the image out of proportion. Instead check out this quick tutorial that shows different methods for applying background images using CSS.

IntelliJ IDEA shows errors when using Spring's @Autowired annotation

Got the same error here!

It seems the Intellij cannot verify if the class implementation is a @Service or @Component.

Solve it just changing from Error to Warning(Pressing Alt + Enter).

LocalDate to java.util.Date and vice versa simplest conversion?


Is there a simple way to convert a LocalDate (introduced with Java 8) to java.util.Date object? By 'simple', I mean simpler than this

Nope. You did it properly, and as concisely as possible.

java.util.Date.from(                     // Convert from modern java.time class to troublesome old legacy class.  DO NOT DO THIS unless you must, to inter operate with old code not yet updated for java.time.
    myLocalDate                          // `LocalDate` class represents a date-only, without time-of-day and without time zone nor offset-from-UTC. 
    .atStartOfDay(                       // Let java.time determine the first moment of the day on that date in that zone. Never assume the day starts at 00:00:00.
        ZoneId.of( "America/Montreal" )  // Specify time zone using proper name in `continent/region` format, never 3-4 letter pseudo-zones such as “PST”, “CST”, “IST”. 
    )                                    // Produce a `ZonedDateTime` object. 
    .toInstant()                         // Extract an `Instant` object, a moment always in UTC.

Read below for issues, and then think about it. How could it be simpler? If you ask me what time does a date start, how else could I respond but ask you “Where?”?. A new day dawns earlier in Paris FR than in Montréal CA, and still earlier in Kolkata IN, and even earlier in Auckland NZ, all different moments.

So in converting a date-only (LocalDate) to a date-time we must apply a time zone (ZoneId) to get a zoned value (ZonedDateTime), and then move into UTC (Instant) to match the definition of a java.util.Date.


Firstly, avoid the old legacy date-time classes such as java.util.Date whenever possible. They are poorly designed, confusing, and troublesome. They were supplanted by the java.time classes for a reason, actually, for many reasons.

But if you must, you can convert to/from java.time types to the old. Look for new conversion methods added to the old classes.

Table of all date-time types in Java, both modern and legacy

java.util.Date ? java.time.LocalDate

Keep in mind that a java.util.Date is a misnomer as it represents a date plus a time-of-day, in UTC. In contrast, the LocalDate class represents a date-only value without time-of-day and without time zone.

Going from java.util.Date to java.time means converting to the equivalent class of java.time.Instant. The Instant class represents a moment on the timeline in UTC with a resolution of nanoseconds (up to nine (9) digits of a decimal fraction).

Instant instant = myUtilDate.toInstant();

The LocalDate class represents a date-only value without time-of-day and without time zone.

A time zone is crucial in determining a date. For any given moment, the date varies around the globe by zone. For example, a few minutes after midnight in Paris France is a new day while still “yesterday” in Montréal Québec.

So we need to move that Instant into a time zone. We apply ZoneId to get a ZonedDateTime.

ZoneId z = ZoneId.of( "America/Montreal" );
ZonedDateTime zdt = instant.atZone( z );

From there, ask for a date-only, a LocalDate.

LocalDate ld = zdt.toLocalDate();

java.time.LocalDate ? java.util.Date

To move the other direction, from a java.time.LocalDate to a java.util.Date means we are going from a date-only to a date-time. So we must specify a time-of-day. You probably want to go for the first moment of the day. Do not assume that is 00:00:00. Anomalies such as Daylight Saving Time (DST) means the first moment may be another time such as 01:00:00. Let java.time determine that value by calling atStartOfDay on the LocalDate.

ZonedDateTime zdt = myLocalDate.atStartOfDay( z );

Now extract an Instant.

Instant instant = zdt.toInstant();

Convert that Instant to java.util.Date by calling from( Instant ).

java.util.Date d = java.util.Date.from( instant );

More info

About java.time

The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.

To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.

The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.

You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes. Hibernate 5 & JPA 2.2 support java.time.

Where to obtain the java.time classes?

Table of which java.time library to use with which version of Java or Android

The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.

Refer to a cell in another worksheet by referencing the current worksheet's name?

Here is how I made monthly page in similar manner as Fernando:

  1. I wrote manually on each page number of the month and named that place as ThisMonth. Note that you can do this only before you make copies of the sheet. After copying Excel doesn't allow you to use same name, but with sheet copy it does it still. This solution works also without naming.
  2. I added number of weeks in the month to location C12. Naming is fine also.
  3. I made five weeks on every page and on fifth week I made function


    that empties fifth week if this month has only four weeks. C12 holds the number of weeks.

  4. ...
  5. I created annual Excel, so I had 12 sheets in it: one for each month. In this example name of the sheet is "Month". Note that this solutions works also with the ODS file standard except you need to change all spaces as "_" characters.
  6. I renamed first "Month" sheet as "Month (1)" so it follows the same naming principle. You could also name it as "Month1" if you wish, but "January" would require a bit more work.
  7. Insert following function on the first day field starting sheet #2:

     =INDIRECT(CONCATENATE("'Month (",ThisMonth-1,")'!B15"))+INDIRECT(CONCATENATE("'Month (",ThisMonth-1,")'!C12"))*7

    So in another word, if you fill four or five weeks on the previous sheet, this calculates date correctly and continues from correct date.

How to add an action to a UIAlertView button using Swift iOS

Swift 4 Update

        // Create the alert controller
        let alertController = UIAlertController(title: "Title", message: "Message", preferredStyle: .alert)

        // Create the actions
        let okAction = UIAlertAction(title: "OK", style: UIAlertActionStyle.default) {
            UIAlertAction in
            NSLog("OK Pressed")
        let cancelAction = UIAlertAction(title: "Cancel", style: UIAlertActionStyle.cancel) {
            UIAlertAction in
            NSLog("Cancel Pressed")

        // Add the actions

        // Present the controller
        self.present(alertController, animated: true, completion: nil)

How to ssh from within a bash script?

What you need to do is to exchange the SSH keys for the user the script runs as. Have a look at this tutorial

After doing so, your scripts will run without the need for entering a password. But, for security's sake, you don't want to do this for root users!

How do I escape double and single quotes in sed?

My problem was that I needed to have the "" outside the expression since I have a dynamic variable inside the sed expression itself. So than the actual solution is that one from lenn jackman that you replace the " inside the sed regex with [\"].

So my complete bash is:


sed -i -e "s#value=[\"]trunk[\"]#value=\"tags/$RELEASE_VERSION\"#g" myfile.xml

Here is:

# is the sed separator

[\"] = " in regex

value = \"tags/$RELEASE_VERSION\" = my replacement string, important it has just the \" for the quotes

How to check if an Object is a Collection Type in Java?

if (x instanceof Collection<?>){

if (x instanceof Map<?,?>){

Parsing boolean values with argparse

Simplest & most correct way is:

from distutils.util import strtobool

parser.add_argument('--feature', dest='feature', 
                    type=lambda x: bool(strtobool(x)))

Do note that True values are y, yes, t, true, on and 1; false values are n, no, f, false, off and 0. Raises ValueError if val is anything else.

UTF-8 text is garbled when form is posted as multipart/form-data

I think i'am late for the party but when you use a wildfly, you can add an default-encoding to the standalone.xml. Just search in the standalone.xml for

<servlet-container name="default"> 

and add encoding like this:

<servlet-container name="default" default-encoding="UTF-8">

How to convert List<string> to List<int>?

You can use it via LINQ

     var selectedEditionIds = input.SelectedEditionIds.Split(",").ToArray()
                            .Where(i => !string.IsNullOrWhiteSpace(i) 
                             && int.TryParse(i,out int validNumber))

Facebook API - How do I get a Facebook user's profile image through the Facebook API (without requiring the user to "Allow" the application)

Simple one-line code to save FULL size profile image on your server.


copy("", "picture.jpg");


This will only work if openssl is enabled in php.ini.

Clear contents of cells in VBA using column reference

As Gary's Student mentioned, you would need to remove the dot before Cells to make the code work as you originally wrote it. I can't be sure, since you only included the one line of code, but the error you got when you deleted the dots might have something to do with how you defined your variables.

I ran your line of code with the variables defined as integers and it worked:

Sub TestClearLastColumn()

    Dim LastColData As Long
        Set LastColData = Range("A1").End(xlToRight).Column

    Dim LastRowData As Long
        Set LastRowData = Range("A1").End(xlDown).Row

    Worksheets("Sheet1").Range(Cells(2, LastColData), Cells(LastRowData, LastColData)).ClearContents

End Sub

I don't think a With statement is appropriate to the line of code you shared, but if you were to use one, the With would be at the start of the line that defines the object you are manipulating. Here is your code rewritten using an unnecessary With statement:

With Worksheets("Sheet1").Range(Cells(2, LastColData), Cells(LastRowData, LastColData))
End With

With statements are designed to save you from retyping code and to make your coding easier to read. It becomes useful and appropriate if you do more than one thing with an object. For example, if you wanted to also turn the column red and add a thick black border, you might use a With statement like this:

With Worksheets("Sheet1").Range(Cells(2, LastColData), Cells(LastRowData, LastColData))
    .Interior.Color = vbRed
    .BorderAround Color:=vbBlack, Weight:=xlThick
End With

Otherwise you would have to declare the range for each action or property, like this:

    Worksheets("Sheet1").Range(Cells(2, LastColData), Cells(LastRowData, LastColData)).ClearContents
    Worksheets("Sheet1").Range(Cells(2, LastColData), Cells(LastRowData, LastColData)).Interior.Color = vbRed
    Worksheets("Sheet1").Range(Cells(2, LastColData), Cells(LastRowData, LastColData)).BorderAround Color:=vbBlack, Weight:=xlThick

I hope this gives you a sense for why Gary's Student believed the compiler might be expecting a With (even though it was inappropriate) and how and when a With can be useful in your code.

Reading rows from a CSV file in Python

You could do something like this:

with open("data1.txt") as f:
    lis = [line.split() for line in f]        # create a list of lists
    for i, x in enumerate(lis):              #print the list items 
        print "line{0} = {1}".format(i, x)

# output 
line0 = ['Year:', 'Dec:', 'Jan:']
line1 = ['1', '50', '60']
line2 = ['2', '25', '50']
line3 = ['3', '30', '30']
line4 = ['4', '40', '20']
line5 = ['5', '10', '10']

or :

with open("data1.txt") as f:
    for i, line in enumerate(f):             
        print "line {0} = {1}".format(i, line.split())

# output         
line 0 = ['Year:', 'Dec:', 'Jan:']
line 1 = ['1', '50', '60']
line 2 = ['2', '25', '50']
line 3 = ['3', '30', '30']
line 4 = ['4', '40', '20']
line 5 = ['5', '10', '10']


with open('data1.txt') as f:
    print "{0}".format(f.readline().split())
    for x in f:
        x = x.split()
        print "{0} = {1}".format(x[0],sum(map(int, x[1:])))

# output          
['Year:', 'Dec:', 'Jan:']
1 = 110
2 = 75
3 = 60
4 = 60
5 = 20

Adding rows to dataset

 DataSet ds = new DataSet();

 DataTable dt = new DataTable("MyTable");
 dt.Columns.Add(new DataColumn("id",typeof(int)));
 dt.Columns.Add(new DataColumn("name", typeof(string)));

 DataRow dr = dt.NewRow();
 dr["id"] = 123;
 dr["name"] = "John";

How can I scale the content of an iframe?

After struggling with this for hours trying to get it to work in IE8, 9, and 10 here's what worked for me.

This stripped-down CSS works in FF 26, Chrome 32, Opera 18, and IE9 -11 as of 1/7/2014:

    width: 320px;
    height: 192px;
    padding: 0;
    overflow: hidden;

    width: 1280px;
    height: 786px;
    border: 0;

    -ms-transform: scale(0.25);
    -moz-transform: scale(0.25);
    -o-transform: scale(0.25);
    -webkit-transform: scale(0.25);
    transform: scale(0.25);

    -ms-transform-origin: 0 0;
    -moz-transform-origin: 0 0;
    -o-transform-origin: 0 0;
    -webkit-transform-origin: 0 0;
    transform-origin: 0 0;

For IE8, set the width/height to match the iframe, and add -ms-zoom to the .wrap container div:

    width: 1280px; /* same size as frame */
    height: 768px;
    -ms-zoom: 0.25; /* for IE 8 ONLY */

Just use your favorite method for browser sniffing to conditionally include the appropriate CSS, see Is there a way to do browser specific conditional CSS inside a *.css file? for some ideas.

IE7 was a lost cause since -ms-zoom did not exist until IE8.

Here's the actual HTML I tested with:

<div class="wrap">
   <iframe class="frame" src=""></iframe>
<div class="wrap">
    <iframe class="frame" src=""></iframe>

How can I convert a .jar to an .exe?

Launch4j works on both Windows and Linux/Mac. But if you're running Linux/Mac, there is a way to embed your jar into a shell script that performs the autolaunch for you, so you have only one runnable file:

MYSELF=`which "$0" 2>/dev/null`
[ $? -gt  0 -a -f "$0" ] && MYSELF="./$0"
# Parse options to determine which ones are for Java and which ones are for the Program
while [ $# -gt 0 ] ; do
    case $1 in
        -Xm*) JAVA_OPT="$JAVA_OPT $1" ;;
        -D*)  JAVA_OPT="$JAVA_OPT $1" ;;
        *)    PROG_OPT="$PROG_OPT $1" ;;
exec java $JAVA_OPT -jar $MYSELF $PROG_OPT

Then you create your runnable file from your jar:

$ cat myrunnablejar.jar > myrunnable
$ chmod +x myrunnable

It works the same way launch4j works: because a jar has a zip format, which header is located at the end of the file. You can have any header you want (either binary executable or, like here, shell script) and run java -jar <myexe>, as <myexe> is a valid zip/jar file.

how to convert string into dictionary in python 3.*?

  1. literal_eval, a somewhat safer version of eval (will only evaluate literals ie strings, lists etc):

    from ast import literal_eval
    python_dict = literal_eval("{'a': 1}")
  2. json.loads but it would require your string to use double quotes:

    import json
    python_dict = json.loads('{"a": 1}')

How to pass in password to pg_dump?

the easiest way in my opinion, this: you edit you main postgres config file: pg_hba.conf there you have to add the following line:

host <you_db_name> <you_db_owner> trust

and after this you need start you cron thus:

pg_dump -h -U <you_db_user> <you_db_name> | gzip > /backup/db/$(date +%Y-%m-%d).psql.gz

and it worked without password

How to use Microsoft.Office.Interop.Excel on a machine without installed MS Office?

you can create a service and generate excel on server and then allow clients download excel. cos buying excel license for 1000 ppl, it is better to have one license for server.

hope that helps.

JDK was not found on the computer for NetBeans 6.5

I face the same problem while installing the NetBeans but I did the installation part properly simply you have do is 1-> GO and download the JRE file of java link ->

2-> After installing the JRE kindly go to directory where you have install the JRE 3-> And copy all the file of from the JRE folder 4-> And paste in the jdk folder but 5-> while copying the file make sure you replace-and-copy the file while any prompt pop out

6-> Then open the command prompt(cmd) and simply type 7->netbeans-8.2-windows.exe --javahome "path-of-your-jdk-file"

Read/write to file using jQuery

No, JavaScript doesn't have access to writing files as this would be a huge security risk to say the least. If you wanted to get/store information server-side, though, you can certainly make an Ajax call to a PHP/ASP/Python/etc. script that can then get/store the data in the server. If you meant store data on the client machine, this is impossible with JavaScript alone. I suspect Flash/Java may be able to, but I am not sure.

If you are only trying to store a small amount of information for an unreliable period of time regarding a specific user, I think you want Web Storage API or cookies. I am not sure from your question what you are trying to accomplish, though.

Select Top and Last rows in a table (SQL server)

To get the bottom 1000 you will want to order it by a column in descending order, and still take the top 1000.

FROM [SomeTable]

If you care for it to be in the same order as before you can use a common table expression for that:

    SELECT TOP 1000 *
    FROM [SomeTable]
    ORDER BY MySortColumn DESC

ORDER BY MySortColumn

Using Selenium Web Driver to retrieve value of a HTML input

This is kind of hacky, but it works.

I used JavascriptExecutor and added a div to the HTML, and changed the text in the div to $('#prettyTime').val() I then used Selenium to retrieve the div and grab its value. After testing the correctness of the value, I removed the div that was just created.

Adding days to a date in Java

SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yyyy");
Calendar c = Calendar.getInstance();
c.setTime(new Date()); // Now use today date.
c.add(Calendar.DATE, 5); // Adding 5 days
String output = sdf.format(c.getTime());

Using current time in UTC as default value in PostgreSQL

Function already exists: timezone('UTC'::text, now())

Clear the form field after successful submission of php form

The POST data which holds the submitted form data is being echoed in the form, eg:

<input name="firstname" type="text" placeholder="First Name" required="required" 
value="<?php echo $_POST['firstname'];?>"  

Either clear the POST data once you have done with the form - ie all inputs were ok and you have actioned whatever your result from a form is.
Or, once you have determined the form is ok and have actioned whatever you action from the form, redirect the user to a new page to say "all done, thanks" etc.

header('Location: thanks.php');

This stops the POST data being present, it's know as "Post/Redirect/Get":

The Post/Redirect/Get (PRG) method and using another page also ensures that if users click browser refresh, or back button having navigated somewhere else, your form is not submitted again.
This means if your form inserts into a database, or emails someone (etc), without the PRG method the values will (likely) be inserted/emailed every time they click refresh or revisit the page using their history/back button.

Disabling the long-running-script message in Internet Explorer

The unresponsive script dialog box shows when some javascript thread takes too long too complete. Editing the registry could work, but you would have to do it on all client machines. You could use a "recursive closure" as follows to alleviate the problem. It's just a coding structure in which allows you to take a long running for loop and change it into something that does some work, and keeps track where it left off, yielding to the browser, then continuing where it left off until we are done.

Figure 1, Add this Utility Class RepeatingOperation to your javascript file. You will not need to change this code:

RepeatingOperation = function(op, yieldEveryIteration) {

  //keeps count of how many times we have run heavytask() 
  //before we need to temporally check back with the browser.
  var count = 0;   

  this.step = function() {

    //Each time we run heavytask(), increment the count. When count
    //is bigger than the yieldEveryIteration limit, pass control back 
    //to browser and instruct the browser to immediately call op() so
    //we can pick up where we left off.  Repeat until we are done.
    if (++count >= yieldEveryIteration) {
      count = 0;

      //pass control back to the browser, and in 1 millisecond, 
      //have the browser call the op() function.  
      setTimeout(function() { op(); }, 1, [])

      //The following return statement halts this thread, it gives 
      //the browser a sigh of relief, your long-running javascript
      //loop has ended (even though technically we havn't yet).
      //The browser decides there is no need to alarm the user of
      //an unresponsive javascript process.

Figure 2, The following code represents your code that is causing the 'stop running this script' dialog because it takes so long to complete:

process10000HeavyTasks = function() {
  var len = 10000;  
  for (var i = len - 1; i >= 0; i--) {
    heavytask();   //heavytask() can be run about 20  times before
                   //an 'unresponsive script' dialog appears.
                   //If heavytask() is run more than 20 times in one
                   //javascript thread, the browser informs the user that
                   //an unresponsive script needs to be dealt with.  

                   //This is where we need to terminate this long running
                   //thread, instruct the browser not to panic on an unresponsive
                   //script, and tell it to call us right back to pick up
                   //where we left off.

Figure 3. The following code is the fix for the problematic code in Figure 2. Notice the for loop is replaced with a recursive closure which passes control back to the browser every 10 iterations of heavytask()

process10000HeavyTasks = function() {

  var global_i = 10000; //initialize your 'for loop stepper' (i) here.

  var repeater = new this.RepeatingOperation(function() {


    if (--global_i >= 0){     //Your for loop conditional goes here.
      repeater.step();        //while we still have items to process,
                              //run the next iteration of the loop.
    else {
       alert("we are done");  //when this line runs, the for loop is complete.
  }, 10);                   //10 means process 10 heavytask(), then
                            //yield back to the browser, and have the
                            //browser call us right back.

  repeater.step();          //this command kicks off the recursive closure.


Adapted from this source:

Credit card payment gateway in PHP?

Braintree also has an open source PHP library that makes PHP integration pretty easy.

Form inside a form, is that alright?

Yes there is. It is wrong. It won't work because it is wrong. Most browsers will only see one form.

Difference between View and Request scope in managed beans

A @ViewScoped bean lives exactly as long as a JSF view. It usually starts with a fresh new GET request, or with a navigation action, and will then live as long as the enduser submits any POST form in the view to an action method which returns null or void (and thus navigates back to the same view). Once you refresh the page, or return a non-null string (even an empty string!) navigation outcome, then the view scope will end.

A @RequestScoped bean lives exactly as long a HTTP request. It will thus be garbaged by end of every request and recreated on every new request, hereby losing all changed properties.

A @ViewScoped bean is thus particularly more useful in rich Ajax-enabled views which needs to remember the (changed) view state across Ajax requests. A @RequestScoped one would be recreated on every Ajax request and thus fail to remember all changed view state. Note that a @ViewScoped bean does not share any data among different browser tabs/windows in the same session like as a @SessionScoped bean. Every view has its own unique @ViewScoped bean.

See also:

Using mysql concat() in WHERE clause?

What you have should work but can be reduced to:

select * from table where concat_ws(' ',first_name,last_name) 
like '%$search_term%';

Can you provide an example name and search term where this doesn't work?

Cross-reference (named anchor) in markdown

Late to the party, but I think this addition might be useful for people working with rmarkdown. In rmarkdown there is built-in support for references to headers in your document.

Any header defined by

# Header

can be referenced by

get me back to that [header](#header)

The following is a minimal standalone .rmd file that shows this behavior. It can be knitted to .pdf and .html.

title: "references in rmarkdown"
  html_document: default
  pdf_document: default

# Header

Write some more text. Write some more text. Write some more text. Write some more text. Write some more text. Write some more text. Write some more text. Write some more text. Write some more text. Write some more text. Write some more text. 

Go back to that [header](#header).

Pass form data to another page with php

The best way to accomplish that is to use POST which is a method of Hypertext Transfer Protocol



<form action="site2.php" method="post">
Name: <input type="text" name="name">
Email: <input type="text" name="email">
<input type="submit">




 Hello <?php echo $_POST["name"]; ?>!<br>
 Your mail is <?php echo $_POST["mail"]; ?>.



Hello "name" !

Your email is "[email protected]" .

Rename multiple files by replacing a particular pattern in the filenames using a shell script

You can use rename utility to rename multiple files by a pattern. For example following command will prepend string MyVacation2011_ to all the files with jpg extension.

rename 's/^/MyVacation2011_/g' *.jpg


rename <pattern> <replacement> <file-list>

jQuery using append with effects

In my case:

$("div.which-stores-content").append("<div class="content">Content</div>);

you can adjust your css with visibility:hidden -> visibility:visible and adjust the transitions etc transition: visibility 1.0s;

File to byte[] in Java

Guava has Files.toByteArray() to offer you. It has several advantages:

  1. It covers the corner case where files report a length of 0 but still have content
  2. It's highly optimized, you get a OutOfMemoryException if trying to read in a big file before even trying to load the file. (Through clever use of file.length())
  3. You don't have to reinvent the wheel.

Location of the android sdk has not been setup in the preferences in mac os?

This problem seems to arise from new versions of android sdk the solution that worked fine for me was to go to help->check for updates and let that finish once all software in eclipse updated it all seems to work fine. I was using juno and the latest sdk, which I upgraded outside eclipse.

Check if item is in an array / list

Assuming you mean "list" where you say "array", you can do

if item in my_list:
    # whatever

This works for any collection, not just for lists. For dictionaries, it checks whether the given key is present in the dictionary.

LINK : fatal error LNK1561: entry point must be defined ERROR IN VC++

You can get this error if you define a project as an .exe but intent to create a .lib or a .dll

How to split elements of a list?

I had to split a list for feature extraction in two parts lt,lc:

ltexts = ((df4.ix[0:,[3,7]]).values).tolist()

featsets = [(act_features((lt)),lc) 
              for lc, lt in ltexts]

def act_features(atext):
  features = {}
  for word in nltk.word_tokenize(atext):
  return features

How to remove all callbacks from a Handler?

As josh527 said, handler.removeCallbacksAndMessages(null); can work.
But why?
If you have a look at the source code, you can understand it more clearly. There are 3 type of method to remove callbacks/messages from handler(the MessageQueue):

  1. remove by callback (and token)
  2. remove by message.what (and token)
  3. remove by token (leave some overload method)

 * Remove any pending posts of Runnable <var>r</var> with Object
 * <var>token</var> that are in the message queue.  If <var>token</var> is null,
 * all callbacks will be removed.
public final void removeCallbacks(Runnable r, Object token)
    mQueue.removeMessages(this, r, token);

 * Remove any pending posts of messages with code 'what' and whose obj is
 * 'object' that are in the message queue.  If <var>object</var> is null,
 * all messages will be removed.
public final void removeMessages(int what, Object object) {
    mQueue.removeMessages(this, what, object);

 * Remove any pending posts of callbacks and sent messages whose
 * <var>obj</var> is <var>token</var>.  If <var>token</var> is null,
 * all callbacks and messages will be removed.
public final void removeCallbacksAndMessages(Object token) {
    mQueue.removeCallbacksAndMessages(this, token);
} do the real work:

void removeMessages(Handler h, int what, Object object) {
    if (h == null) {

    synchronized (this) {
        Message p = mMessages;

        // Remove all messages at front.
        while (p != null && == h && p.what == what
               && (object == null || p.obj == object)) {
            Message n =;
            mMessages = n;
            p = n;

        // Remove all messages after front.
        while (p != null) {
            Message n =;
            if (n != null) {
                if ( == h && n.what == what
                    && (object == null || n.obj == object)) {
                    Message nn =;
           = nn;
            p = n;

void removeMessages(Handler h, Runnable r, Object object) {
    if (h == null || r == null) {

    synchronized (this) {
        Message p = mMessages;

        // Remove all messages at front.
        while (p != null && == h && p.callback == r
               && (object == null || p.obj == object)) {
            Message n =;
            mMessages = n;
            p = n;

        // Remove all messages after front.
        while (p != null) {
            Message n =;
            if (n != null) {
                if ( == h && n.callback == r
                    && (object == null || n.obj == object)) {
                    Message nn =;
           = nn;
            p = n;

void removeCallbacksAndMessages(Handler h, Object object) {
    if (h == null) {

    synchronized (this) {
        Message p = mMessages;

        // Remove all messages at front.
        while (p != null && == h
                && (object == null || p.obj == object)) {
            Message n =;
            mMessages = n;
            p = n;

        // Remove all messages after front.
        while (p != null) {
            Message n =;
            if (n != null) {
                if ( == h && (object == null || n.obj == object)) {
                    Message nn =;
           = nn;
            p = n;

How can I convert a std::string to int?

ll toll(string a){
    ll ret=0;
    bool minus=false;
    for(auto i:a){
        if(i=='-'){ minus=true; continue; }
    } if(minus) ret*=-1;
    return ret;
    # ll is defined as, #define ll long long int
    # usage: ll a = toll(string("-1234"));

How can I change the font size using seaborn FacetGrid?

For the legend, you can use this

plt.setp(g._legend.get_title(), fontsize=20)

Where g is your facetgrid object returned after you call the function making it.

How to make sure you don't get WCF Faulted state exception?

If the transfer mode is Buffered then make sure that the values of MaxReceivedMessageSize and MaxBufferSize is same. I just resolved the faulted state issue this way after grappling with it for hours and thought i'll post it here if it helps someone.

Failed to find 'ANDROID_HOME' environment variable

This solved my problem. Add below to your system path



ERROR : [Microsoft][ODBC Driver Manager] Data source name not found and no default driver specified

Perform the following steps:

  1. Start the Registry Editor by typing regedit in the Run window.
  2. Select the following key in the registry: HKEY_LOCAL_MACHINE\SOFTWARE\ODBC.
  3. In the Security menu, click Permissions.
  4. Grant Full Permission to the account which is being used for making connections.
  5. Quit the Registry Editor.

Log to the base 2 in python

It's good to know that

alt text

but also know that math.log takes an optional second argument which allows you to specify the base:

In [22]: import math

In [23]: math.log?
Type:       builtin_function_or_method
Base Class: <type 'builtin_function_or_method'>
String Form:    <built-in function log>
Namespace:  Interactive
    log(x[, base]) -> the logarithm of x to the given base.
    If the base not specified, returns the natural logarithm (base e) of x.

In [25]: math.log(8,2)
Out[25]: 3.0

How do I get the parent directory in Python?

The Pathlib method (Python 3.4+)

from pathlib import Path
Path('C:\Program Files').parent
# Returns a Pathlib object

The traditional method

import os.path
os.path.dirname('C:\Program Files')
# Returns a string

Which method should I use?

Use the traditional method if:

  • You are worried about existing code generating errors if it were to use a Pathlib object. (Since Pathlib objects cannot be concatenated with strings.)

  • Your Python version is less than 3.4.

  • You need a string, and you received a string. Say for example you have a string representing a filepath, and you want to get the parent directory so you can put it in a JSON string. It would be kind of silly to convert to a Pathlib object and back again for that.

If none of the above apply, use Pathlib.

What is Pathlib?

If you don't know what Pathlib is, the Pathlib module is a terrific module that makes working with files even easier for you. Most if not all of the built in Python modules that work with files will accept both Pathlib objects and strings. I've highlighted below a couple of examples from the Pathlib documentation that showcase some of the neat things you can do with Pathlib.

Navigating inside a directory tree:

>>> p = Path('/etc')
>>> q = p / 'init.d' / 'reboot'
>>> q
>>> q.resolve()

Querying path properties:

>>> q.exists()
>>> q.is_dir()

Python using enumerate inside list comprehension

Just to be really clear, this has nothing to do with enumerate and everything to do with list comprehension syntax.

This list comprehension returns a list of tuples:

[(i,j) for i in range(3) for j in 'abc']

this a list of dicts:

[{i:j} for i in range(3) for j in 'abc']

a list of lists:

[[i,j] for i in range(3) for j in 'abc']

a syntax error:

[i,j for i in range(3) for j in 'abc']

Which is inconsistent (IMHO) and confusing with dictionary comprehensions syntax:

>>> {i:j for i,j in enumerate('abcdef')}
{0: 'a', 1: 'b', 2: 'c', 3: 'd', 4: 'e', 5: 'f'}

And a set of tuples:

>>> {(i,j) for i,j in enumerate('abcdef')}
set([(0, 'a'), (4, 'e'), (1, 'b'), (2, 'c'), (5, 'f'), (3, 'd')])

As Óscar López stated, you can just pass the enumerate tuple directly:

>>> [t for t in enumerate('abcdef') ] 
[(0, 'a'), (1, 'b'), (2, 'c'), (3, 'd'), (4, 'e'), (5, 'f')]

Convert InputStream to byte array in Java

ByteArrayOutputStream out = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
while (true) {
    int r =;
    if (r == -1) break;
    out.write(buffer, 0, r);

byte[] ret = out.toByteArray();

How to include Authorization header in cURL POST HTTP Request in PHP?

@jason-mccreary is totally right. Besides I recommend you this code to get more info in case of malfunction:

$rest = curl_exec($crl);

if ($rest === false)
    // throw new Exception('Curl error: ' . curl_error($crl));
    print_r('Curl error: ' . curl_error($crl));



To debug you can set CURLOPT_HEADER to true to check HTTP response with firebug::net or similar.

curl_setopt($crl, CURLOPT_HEADER, true);


About Curl error: SSL certificate problem, verify that the CA cert is OK try adding this headers (just to debug, in a production enviroment you should keep these options in true):

curl_setopt($crl, CURLOPT_SSL_VERIFYHOST, false);
curl_setopt($crl, CURLOPT_SSL_VERIFYPEER, false);

When is it acceptable to call GC.Collect?

If you have good reason to believe that a significant set of objects - particularly those you suspect to be in generations 1 and 2 - are now eligible for garbage collection, and that now would be an appropriate time to collect in terms of the small performance hit.

A good example of this is if you've just closed a large form. You know that all the UI controls can now be garbage collected, and a very short pause as the form is closed probably won't be noticeable to the user.

UPDATE 2.7.2018

As of .NET 4.5 - there is GCLatencyMode.LowLatency and GCLatencyMode.SustainedLowLatency. When entering and leaving either of these modes, it is recommended that you force a full GC with GC.Collect(2, GCCollectionMode.Forced).

As of .NET 4.6 - there is the GC.TryStartNoGCRegion method (used to set the read-only value GCLatencyMode.NoGCRegion). This can itself, perform a full blocking garbage collection in an attempt to free enough memory, but given we are disallowing GC for a period, I would argue it is also a good idea to perform full GC before and after.

Source: Microsoft engineer Ben Watson's: Writing High-Performance .NET Code, 2nd Ed. 2018.


In React Native, how do I put a view on top of another view, with part of it lying outside the bounds of the view behind?

import React, {Component} from 'react';
import {StyleSheet, View} from 'react-native';

export default class App extends Component {
  render() {
    return (
       <View>// you need to wrap the two Views an another View
          <View style={styles.box1}></View>
          <View style={styles.box2}></View>

const styles = StyleSheet.create({
    position: 'absolute',


Cannot execute script: Insufficient memory to continue the execution of the program

If you need to connect to LocalDB during development, you can use:

sqlcmd -S "(localdb)\MSSQLLocalDB" -d dbname -i file.sql

Can I map a hostname *and* a port with /etc/hosts?

If you really need to do this, use reverse proxy.

For example, with nginx as reverse proxy

server {
  location / {

Command to find information about CPUs on a UNIX machine

Firstly, it probably depends which version of Solaris you're running, but also what hardware you have.

On SPARC at least, you have psrinfo to show you processor information, which run on its own will show you the number of CPUs the machine sees. psrinfo -p shows you the number of physical processors installed. From that you can deduce the number of threads/cores per physical processors.

prtdiag will display a fair bit of info about the hardware in your machine. It looks like on a V240 you do get memory channel info from prtdiag, but you don't on a T2000. I guess that's an architecture issue between UltraSPARC IIIi and UltraSPARC T1.

How to set time zone of a java.util.Date?

If anyone ever needs this, if you need to convert an XMLGregorianCalendar timezone to your current timezone from UTC, then all you need to do is set the timezone to 0, then call toGregorianCalendar() - it will stay the same timezone, but the Date knows how to convert it to yours, so you can get the data from there.

XMLGregorianCalendar xmlStartTime = DatatypeFactory.newInstance()
GregorianCalendar startCalendar = xmlStartTime.toGregorianCalendar();
Date startDate = startCalendar.getTime();
XMLGregorianCalendar xmlStartTime = DatatypeFactory.newInstance()
xmlStartTime.setYear(startDate.getYear() + 1900);



How to solve a timeout error in Laravel 5

I had a similar problem just now. However, this had nothing to do with modifying the php.ini file. It was from a for loop. If you are having nested for loops, make sure you are using the iterator properly. In my case, I was iterating the outer iterator from my inner iterator.

Updating version numbers of modules in a multi-module Maven project

I encourage you to read the Maven Book about multi-module (reactor) builds.

I meant in particular the following:


should be changed into. Here take care about the not defined version only in parent part it is defined.



This is a better link.

How do I use spaces in the Command Prompt?

I prefer to enclose the command in () which is valid batch which makes it a bit easier to read:

cmd /C ("C:\Program Files (x86)\WinRar\Rar.exe" a "D:\Hello 2\File.rar" "D:\Hello 2\*.*")

Get google map link with latitude/longitude

  <iframe src="'+YOUR_LAT+','+YOUR_LON+'&hl=en&z=14&amp;output=embed" width="100%" height="400" frameborder="0" style="border:0" allowfullscreen></iframe>

put your replace lattitude,longitude values on YOUR_LAT,YOUR_LON respectively. hl parameter for setting language on map, z for zoomlevel;

How to extract elements from a list using indices in Python?

Use Numpy direct array indexing, as in MATLAB, Julia, ...

a = [10, 11, 12, 13, 14, 15];
s = [1, 2, 5] ;

import numpy as np
# [11, 12, 15]

Better yet, just stay with Numpy arrays

a = np.array([10, 11, 12, 13, 14, 15])
#array([11, 12, 15])

How to trigger an event in input text after I stop typing/writing?


Here is the solution. Executing a function after the user has stopped typing for a specified amount of time:

var delay = (function(){
  var timer = 0;
  return function(callback, ms){
  clearTimeout (timer);
  timer = setTimeout(callback, ms);


$('input').keyup(function() {
    alert('Hi, func called');
  }, 1000 );

How to prevent IFRAME from redirecting top-level window

I use sandbox="..."

  • allow-forms allows form submission
  • allow-popups allows popups
  • allow-pointer-lock allows pointer lock
  • allow-same-origin allows the document to maintain its origin
  • allow-scripts allows JavaScript execution, and also allows features to trigger automatically
  • allow-top-navigation allows the document to break out of the frame by navigating the top-level window

Top navigation is what you want to prevent, so leave that out and it will not be allowed. Anything left out will be blocked


        <iframe sandbox="allow-same-origin allow-scripts allow-popups allow-forms" src=""</iframe>

How to enable authentication on MongoDB through Docker?

I want to comment but don't have enough reputation.

The user-adding executable script shown above has to be modified with --authenticationDatabase admin and NEWDATABASENAME.

mongo --authenticationDatabase admin --host localhost -u USER_PREVIOUSLY_DEFINED -p PASS_YOU_PREVIOUSLY_DEFINED NEWDATABASENAME --eval "db.createUser({user: 'NEWUSERNAME', pwd: 'PASSWORD', roles: [{role: 'readWrite', db: 'NEWDATABASENAME'}]});"

Unable to locate tools.jar

tools.jar comes with JDK, but what happens in your case it looks for it within /Java/jre6. Change JAVA_HOME env var to one of your JDK home.

How to get the number of days of difference between two dates on mysql?

Get days between Current date to destination Date

 SELECT DATEDIFF('2019-04-12', CURDATE()) AS days;




Pass user defined environment variable to tomcat

Environment variables can be set, by creating a setenv.bat (windows) or (unix) file in the bin folder of your tomcat installation directory. However, environment variables will not be accessabile from within your code.

System properties are set by -D arguments of the java process. You can define java starting arguments in the environment variable JAVA_OPTS.

My suggestions is the combination of these two mechanisms. In your apache-tomcat-0.0.0\bin\setenv.bat write:


and in your Java code write:


How do you share code between projects/solutions in Visual Studio?

There is a very good case for using "adding existing file links" when reusing code across projects, and that is when you need to reference and support different versions of dependent libraries.

Making multiple assemblies with references to different external assemblies isn't easy to do otherwise without duplicating your code, or utilizing tricks with source code control.

I believe that it's easiest to maintain one project for development and unit test, then to create 'build' projects using existing file links when you need to create the assemblies which reference different versions of those external assemblies.

Angular: date filter adds timezone, how to output UTC?

Since version 1.3.0 AngularJS introduced extra filter parameter timezone, like following:

{{ date_expression | date : format : timezone}}

But in versions 1.3.x only supported timezone is UTC, which can be used as following:

{{ someDate | date: 'MMM d, y H:mm:ss' : 'UTC' }}

Since version 1.4.0-rc.0 AngularJS supports other timezones too. I was not testing all possible timezones, but here's for example how you can get date in Japan Standard Time (JSP, GMT +9):

{{ clock | date: 'MMM d, y H:mm:ss' : '+0900' }}

Here you can find documentation of AngularJS date filters.

NOTE: this is working only with Angular 1.x

Here's working example

403 Forbidden vs 401 Unauthorized HTTP responses

According to RFC 2616 (HTTP/1.1) 403 is sent when:

The server understood the request, but is refusing to fulfill it. Authorization will not help and the request SHOULD NOT be repeated. If the request method was not HEAD and the server wishes to make public why the request has not been fulfilled, it SHOULD describe the reason for the refusal in the entity. If the server does not wish to make this information available to the client, the status code 404 (Not Found) can be used instead

In other words, if the client CAN get access to the resource by authenticating, 401 should be sent.

How to click a link whose href has a certain substring in Selenium?

use driver.findElement(By.partialLinkText("long")).click();

How to set ChartJS Y axis title?

For Chart.js 2.x refer to andyhasit's answer -

For Chart.js 1.x, you can tweak the options and extend the chart type to do this, like so

    name: "LineAlt",
    draw: function () {
        Chart.types.Line.prototype.draw.apply(this, arguments);

        var ctx = this.chart.ctx;;
        // text alignment and color
        ctx.textAlign = "center";
        ctx.textBaseline = "bottom";
        ctx.fillStyle = this.options.scaleFontColor;
        // position
        var x = this.scale.xScalePaddingLeft * 0.4;
        var y = this.chart.height / 2;
        // change origin
        ctx.translate(x, y);
        // rotate text
        ctx.rotate(-90 * Math.PI / 180);
        ctx.fillText(this.datasets[0].label, 0, 0);

calling it like this

var ctx = document.getElementById("myChart").getContext("2d");
var myLineChart = new Chart(ctx).LineAlt(data, {
    // make enough space on the right side of the graph
    scaleLabel: "          <%=value%>"

Notice the space preceding the label value, this gives us space to write the y axis label without messing around with too much of Chart.js internals

Fiddle -

enter image description here

Oracle Sql get only month and year in date datatype

SELECT to_char(to_date(month,'yyyy-mm'),'Mon yyyy'), nos
FROM (SELECT to_char(credit_date,'yyyy-mm') MONTH,count(*) nos
      FROM HCN
      WHERE   TRUNC(CREDIT_dATE) BEtween '01-jul-2014' AND '30-JUN-2015'
GROUP BY to_char(credit_date,'yyyy-mm')
ORDER BY to_char(credit_date,'yyyy-mm') ) mm


Jul 2014        49
Aug 2014        35
Sep 2014        57
Oct 2014        50
Nov 2014        45
Dec 2014        88
Jan 2015       131
Feb 2015       112
Mar 2015        76
Apr 2015        45
May 2015        49
Jun 2015        40

What is the syntax of the enhanced for loop in Java?

  1. Enhanced For Loop (Java)
for (Object obj : list);
  1. Enhanced For Each in arraylist (Java)
ArrayList<Integer> list = new ArrayList<Integer>(); 
list.forEach((n) -> System.out.println(n)); 

Replace all double quotes within String

Would not that have to be:


FIVE backslashes in the replacement String.

How do I detect a click outside an element?

For touch devices like iPad and iPhone we can use this code:

$(document).on('touchstart', function (event) {
    var container = $("YOUR CONTAINER SELECTOR");

    if (! &&            // If the target of the click isn't the container...
        container.has( === 0) // ... nor a descendant of the container

Is the practice of returning a C++ reference variable evil?

No. No, no, a thousand times no.

What is evil is making a reference to a dynamically allocated object and losing the original pointer. When you new an object you assume an obligation to have a guaranteed delete.

But have a look at, eg, operator<<: that must return a reference, or

cout << "foo" << "bar" << "bletch" << endl ;

won't work.

Stretch and scale a CSS image in the background - with CSS only


html,body {
    background: url(images/bg.jpg) no-repeat center center fixed;
    -webkit-background-size: cover; /* For WebKit*/
    -moz-background-size: cover;    /* Mozilla*/
    -o-background-size: cover;      /* Opera*/
    background-size: cover;         /* Generic*/

JUnit 4 compare Sets

I like the solution of Hans-Peter Störr... But I think it is not quite correct. Sadly containsInAnyOrder does not accept a Collection of objetcs to compare to. So it has to be a Collection of Matchers:

assertThat(set1, containsInAnyOrder(

The import are:

import static;
import static org.hamcrest.Matchers.containsInAnyOrder;
import static org.junit.Assert.assertThat;

How do I cast a string to integer and have 0 in case of error in the cast with PostgreSQL?

I had the same sort of need and found this to work well for me (postgres 8.4):


Some test cases to demonstrate:

db=> select CAST((COALESCE(NULL,'0')) AS INTEGER);
(1 row)

db=> select CAST((COALESCE('','0')) AS INTEGER);
(1 row)

db=> select CAST((COALESCE('4','0')) AS INTEGER);
(1 row)

db=> select CAST((COALESCE('bad','0')) AS INTEGER);
ERROR:  invalid input syntax for integer: "bad"

If you need to handle the possibility of the field having non-numeric text (such as "100bad") you can use regexp_replace to strip non-numeric characters before the cast.

CAST(REGEXP_REPLACE(COALESCE(myfield,'0'), '[^0-9]+', '', 'g') AS INTEGER)

Then text/varchar values like "b3ad5" will also give numbers

db=> select CAST(REGEXP_REPLACE(COALESCE('b3ad5','0'), '[^0-9]+', '', 'g') AS INTEGER);
(1 row)

To address Chris Cogdon's concern with the solution not giving 0 for all cases, including a case such as "bad" (no digit characters at all), I made this adjusted statement:

CAST((COALESCE(NULLIF(REGEXP_REPLACE(myfield, '[^0-9]+', '', 'g'), ''), '0')) AS INTEGER);

It works similar to the simpler solutions, except will give 0 when the value to convert is non-digit characters only, such as "bad":

db=> select CAST((COALESCE(NULLIF(REGEXP_REPLACE('no longer bad!', '[^0-9]+', '', 'g'), ''), '0')) AS INTEGER);
(1 row)

What is the list of supported languages/locales on Android?

The best way to see the supported list is to start up the emulator in the latest version and open the "Custom Locale" app. This will list all of the supported languages and locales for that version of Android.

Custom Locale App

Is Task.Result the same as .GetAwaiter.GetResult()?

Pretty much. One small difference though: if the Task fails, GetResult() will just throw the exception caused directly, while Task.Result will throw an AggregateException. However, what's the point of using either of those when it's async? The 100x better option is to use await.

Also, you're not meant to use GetResult(). It's meant to be for compiler use only, not for you. But if you don't want the annoying AggregateException, use it.

EXCEL Multiple Ranges - need different answers for each range

Nested if's in Excel Are ugly:

=If(G2 < 1, .1, IF(G2 < 5,.15,if(G2 < 15,.2,if(G2 < 30,.5,if(G2 < 100,.1,1.3)))))

That should cover it.

Java socket API: How to tell if a connection has been closed?

I think this is nature of tcp connections, in that standards it takes about 6 minutes of silence in transmission before we conclude that out connection is gone! So I don`t think you can find an exact solution for this problem. Maybe the better way is to write some handy code to guess when server should suppose a user connection is closed.

Find a private field with Reflection?

I use this method personally

if (typeof(Foo).GetFields(BindingFlags.NonPublic | BindingFlags.Instance).Any(c => c.GetCustomAttributes(typeof(SomeAttribute), false).Any()))
    // do stuff

Switch focus between editor and integrated terminal in Visual Studio Code

A little late to the game but I configured mine as the following in the keybindings.json:

    "key": "ctrl+`",
    "command": "workbench.action.terminal.focus",
    "when": "editorTextFocus"
    "key": "ctrl+`",
    "command": "workbench.action.focusActiveEditorGroup",
    "when": "terminalFocus"
    "key": "alt+`",
    "command": "workbench.action.terminal.toggleTerminal"

I wanted separate keys for opening/closing terminal and switching focus back and forth between the windows.

What are the Android SDK build-tools, platform-tools and tools? And which version should be used?

I'll leave the discussion of the difference between Build Tools, Platform Tools, and Tools to others. From a practical standpoint, you only need to know the answer to your second question:

Which version should be used?

Answer: Use the most recent version.

For those using Android Studio with Gradle, the buildToolsVersion has to be set in the build.gradle (Module: app) file.

android {
    compileSdkVersion 25
    buildToolsVersion "25.0.2"


Where do I get the most recent version number of Build Tools?

Open the Android SDK Manager.

  • In Android Studio go to Tools > Android > SDK Manager > Appearance & Behavior > System Settings > Android SDK
  • Choose the SDK Tools tab.
  • Select Android SDK Build Tools from the list
  • Check Show Package Details.

The last item will show the most recent version.

enter image description here

Make sure it is installed and then write that number as the buildToolsVersion in build.gradle (Module: app).

If input value is blank, assign a value of "empty" with Javascript

If you're using pure JS you can simply do it like:

var input = document.getElementById('myInput');

if(input.value.length == 0)
    input.value = "Empty";

Here's a demo:

Find and replace - Add carriage return OR Newline

If you want to avoid the hassle of escaping the special characters in your search and replacement string when using regular expressions, do the following steps:

  1. Search for your original string, and replace it with "UniqueString42", with regular expressions off.
  2. Search for "UniqueString42" and replace it with "UniqueString42\nUniqueString1337", with regular expressions on
  3. Search for "UniqueString42" and replace it with the first line of your replacement (often your original string), with regular expressions off.
  4. Search for "UniqueString42" and replace it with the second line of your replacement, with regular expressions off.

Note that even if you want to manually pich matches for the first search and replace, you can safely use "replace all" for the three last steps.


For example, if you want to replace this:

public IFoo SomeField { get { return this.SomeField; } }

with that:

public IFoo Foo { get { return this.MyFoo; } }
public IBar Bar { get { return this.MyBar; } }

You would do the following substitutions:

  1. public IFoo SomeField { get { return this.SomeField; } } ? XOXOXOXO (regex off).
  3. XOXOXOXO ? public IFoo Foo { get { return this.MyFoo; } } (regex off).
  4. HUHUHUHU ? public IFoo Bar { get { return this.MyBar; } } (regex off).

how to get the ipaddress of a virtual box running on local machine

Login to virtual machine use below command to check ip address. (anyone will work)

  1. ifconfig
  2. ip addr show

If you used NAT for your virtual machine settings(your machine ip will be, then you have to use port forwarding to connect to machine. IP address will be

If you used bridged networking/Host only networking, then you will have separate Ip address. Use that IP address to connect virtual machine

Git: How to rebase to a specific commit?

Use the "onto" option:

git rebase --onto master^ D^ D

PHP check whether property exists in object or class

Using array_key_exists() on objects is Deprecated in php 7.4

Instead either isset() or property_exists() should be used

reference :

What's the Android ADB shell "dumpsys" tool and what are its benefits?

According to official Android information about dumpsys:

The dumpsys tool runs on the device and provides information about the status of system services.

To get a list of available services use

adb shell dumpsys -l

org.hibernate.MappingException: Unknown entity: annotations.Users

If you are using 5.0x version,configuration with standard service registry is deprecated.

Instead you should bootstrap it with Metadata: In your HibernateUtil class, you should add

private static SessionFactory buildSessionFactory() {
    try {           
        StandardServiceRegistry standardRegistry = new StandardServiceRegistryBuilder()
            .configure( "hibernate.cfg.xml" )

        Metadata metadata = new MetadataSources( standardRegistry )

        return metadata.getSessionFactoryBuilder().build();
    } catch(...) {

Python: Assign Value if None Exists

I'm also coming from Ruby so I love the syntax foo ||= 7.

This is the closest thing I can find.

foo = foo if 'foo' in vars() else 7

I've seen people do this for a dict:

except KeyError:
    foo['bar'] = 7

Upadate: However, I recently found this gem:

foo['bar'] = foo.get('bar', 7)

If you like that, then for a regular variable you could do something like this:

vars()['foo'] = vars().get('foo', 7)

Center Triangle at Bottom of Div

I know this isn't a direct answer to your question, but you could also consider using clip-path, as in this question:

Leaflet - How to find existing markers, and delete markers?

What I did to remove marker was this create a button who allow me do it

Hope i can help someone :)

//Button who active deleteBool
const button = document.getElementById('btn')

//Boolean who let me delete marker
let deleteBool = false

//Button function to enable boolean
  deleteBool = true

// Function to delete marker 
const deleteMarker = (e) => {
    if (deleteBool) {
        deleteBooly = false

//Initiate map
var map ='map').setView([51.505, -0.09], 13);

//Create one marker
let marker = L.marker([51.5, -0.09]).addTo(map)
//Add Marker Function
marker.on('click', deleteMarker)
body {
  display: flex;
  flex-direction: column;

  width: 500px;
  height: 500px;
  margin: auto;

  width: 50px;
  height: 50px;
  margin: 2em auto; 
<!DOCTYPE html>
<html lang="en">

    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <link rel="stylesheet" href="style.css" />
    <link rel="stylesheet" href="[email protected]/dist/leaflet.css" integrity="sha512-xodZBNTC5n17Xt2atTPuE1HxjVMSvLVW9ocqUKLsCC5CXdbqCmblAshOMAS6/keqq/sMZMZ19scR4PsZChSR7A==" crossorigin="" />

    <div id="map"></div>
    <button id="btn">Click me!</button>
    <script script="script" src="[email protected]/dist/leaflet.js" integrity="sha512-XQoYMqMTK8LvdxXYG3nZ448hOEQiglfqkJs1NOQV44cWnUrBc8PkAOcXy20w0vlaXaVUearIOBhiXZ5V3ynxwA==" crossorigin=""></script>
    <script src="script.js"></script>


DataGridView - how to set column width?

i suggest to give a width to all the grid's columns like this :

DataGridViewTextBoxColumn col = new DataGridViewTextBoxColumn();
col.HeaderText = "phone"            
col.Width = 120;
col.DataPropertyName = (if you use a datasource)

and for the main(or the longest) column(let's say address) do this :

col = new DataGridViewTextBoxColumn();
col.HeaderText = "address";
col.Width = 120;

tricky part

col.MinimumWidth = 120;
col.AutoSizeMode = DataGridViewAutoSizeColumnMode.Fill;

tricky part

col.DataPropertyName = (same as above)

In this way, if you stretch the form (and the grid is "dock filled" in his container) the main column, in this case the address column, takes all the space available, but it never goes less than col.MinimumWidth, so it's the only one that is resized.

I use it, when i have a grid and its last column is used for display an image (like icon detail or icon delete..) and it doesn't have the header and it has to be always the smallest one.


A real problem often exists because any variables set inside will not be exported when that batch file finishes. So its not possible to export, which caused us issues. As a result, I just set the registry to ALWAYS used delayed expansion (I don't know why it's not the default, could be speed or legacy compatibility issue.)

Writing a list to a file with Python

Let avg be the list, then:

In [29]: a = n.array((avg))
In [31]: a.tofile('avgpoints.dat',sep='\n',dtype = '%f')

You can use %e or %s depending on your requirement.

converting a base 64 string to an image and saving it

Here is what I ended up going with.

    private void SaveByteArrayAsImage(string fullOutputPath, string base64String)
        byte[] bytes = Convert.FromBase64String(base64String);

        Image image;
        using (MemoryStream ms = new MemoryStream(bytes))
            image = Image.FromStream(ms);

        image.Save(fullOutputPath, System.Drawing.Imaging.ImageFormat.Png);

SQL Server Jobs with SSIS packages - Failed to decrypt protected XML node "DTS:Password" with error 0x8009000B

Change both Project and Package Properties ProtectionLevel to "DontSaveSensitive"

How to get current class name including package name in Java?

The fully-qualified name is opbtained as follows:

String fqn = YourClass.class.getName();

But you need to read a classpath resource. So use

InputStream in = YourClass.getResourceAsStream("resource.txt");

What is the correct way to represent null XML elements?

In many cases the purpose of a Null value is to serve for a data value that was not present in a previous version of your application.

So say you have an xml file from your application "ReportMaster" version 1.

Now in ReportMaster version 2 a some more attributes have been added that may or not be defined.

If you use the 'no tag means null' representation you get automatic backward compatibility for reading your ReportMaster 1 xml file.

How to find a string inside a entire database?

In oracle you can use the following sql command to generate the sql commands you need:

     "select * "
     " from "||table_name||
     " where "||column_name||" like '%123abcd%' ;" as sql_command
from user_tab_columns
where data_type='VARCHAR2';

With ' N ' no of nodes, how many different Binary and Binary Search Trees possible?

The correct answer should be 2nCn/(n+1) for unlabelled nodes and if the nodes are labelled then (2nCn)*n!/(n+1).

How do I clone a job in Jenkins?

Jenkins 2.9

  1. Jenkins > New Item

    Jenkins New Item

  2. Enter an item name - E.g. "MY_CLONE"

    Enter an item name

  3. Specify the source (Copy from) job > OK

    When you start typing the name, the existing values will be found. Notice that this is case sensitive.

    Copy from OK

  4. Click on Save if you want to keep the default values.

  5. Now both jobs are available in the same location:

    View jobs

Take the content of a list and append it to another list

To recap on the previous answers. If you have a list with [0,1,2] and another one with [3,4,5] and you want to merge them, so it becomes [0,1,2,3,4,5], you can either use chaining or extending and should know the differences to use it wisely for your needs.

Extending a list

Using the list classes extend method, you can do a copy of the elements from one list onto another. However this will cause extra memory usage, which should be fine in most cases, but might cause problems if you want to be memory efficient.

a = [0,1,2]
b = [3,4,5]

enter image description here

Chaining a list

Contrary you can use itertools.chain to wire many lists, which will return a so called iterator that can be used to iterate over the lists. This is more memory efficient as it is not copying elements over but just pointing to the next list.

import itertools
a = [0,1,2]
b = [3,4,5]
c = itertools.chain(a, b)

enter image description here

Make an iterator that returns elements from the first iterable until it is exhausted, then proceeds to the next iterable, until all of the iterables are exhausted. Used for treating consecutive sequences as a single sequence.

percentage of two int?

Two options:

Do the division after the multiplication:

int n = 25;
int v = 100;
int percent = n * 100 / v;

Convert an int to a float before dividing

int n = 25;
int v = 100;
float percent = n * 100f / v;
//  float percent = (float) n * 100 / v;
//  float percent = n * 100 / (float) v;

Is there an opposite to display:none?

You can use this display:block; and also add overflow:hidden;

How to force div to appear below not next to another?

#similar { 

Owl Carousel Won't Autoplay

Your Javascript should be


// Most important owl features

autoplay: false,
autoplayTimeout: 5000,
autoplayHoverPause: true

Read file-contents into a string in C++

The most efficient is to create a buffer of the correct size and then read the file into the buffer.

#include <fstream>
#include <vector>

int main()
    std::ifstream       file("Plop");
    if (file)
         * Get the size of the file
        std::streampos          length = file.tellg();

         * Use a vector as the buffer.
         * It is exception safe and will be tidied up correctly.
         * This constructor creates a buffer of the correct length.
         * Because char is a POD data type it is not initialized.
         * Then read the whole file into the buffer.
        std::vector<char>       buffer(length);[0],length);

How can I develop for iPhone using a Windows development machine?

You can use WinChain

Quoting the project page:

It's the easiest way to build the iPhone toolchain on a Windows XP/Vista computer, which in turn, can take Objective-C source code that you write using their UIKit Headers (included with winChain) and compile it into an application that you can use on your iPhone.

How to embed an autoplaying YouTube video in an iframe?

The embedded code of youtube has autoplay off by default. Simply add autoplay=1at the end of "src" attribute. For example:

<iframe src="" width="960" height="447" frameborder="0" allowfullscreen></iframe>

How to extract text from a string using sed?

Try using rextract. It will let you extract text using a regular expression and reformat it.


$ echo "This is 02G05 a test string 20-Jul-2012" | ./rextract '([\d]+G[\d]+)' '${1}'


Converting JSON String to Dictionary Not List

The best way to Load JSON Data into Dictionary is You can user the inbuilt json loader.

Below is the sample snippet that can be used.

import json
f = open("data.json")
data = json.load(f))

What is the proper way to URL encode Unicode characters?

IRI (RFC 3987) is the latest standard that replaces the URI/URL (RFC 3986 and older) standards. URI/URL do not natively support Unicode (well, RFC 3986 adds provisions for future URI/URL-based protocols to support it, but does not update past RFCs). The "%uXXXX" scheme is a non-standard extension to allow Unicode in some situations, but is not universally implemented by everyone. IRI, on the other hand, fully supports Unicode, and requires that text be encoded as UTF-8 before then being percent-encoded.

How do I copy the contents of one ArrayList into another?

You can use such trick:

myObject = new ArrayList<Object>(myTempObject);

or use

myObject = (ArrayList<Object>)myTempObject.clone();

You can get some information about clone() method here

But you should remember, that all these ways will give you a copy of your List, not all of its elements. So if you change one of the elements in your copied List, it will also be changed in your original List.

What is the difference between __dirname and ./ in node.js?

./ refers to the current working directory, except in the require() function. When using require(), it translates ./ to the directory of the current file called. __dirname is always the directory of the current file.

For example, with the following file structure


  "hello": "world"


text file


var fs = require('fs');

console.log(fs.readFileSync('./files/somefile.txt', 'utf8'));

If I cd into /home/user/dir and run node dir.js I will get

{ hello: 'world' }
text file

But when I run the same script from /home/user/ I get

{ hello: 'world' }

Error: ENOENT, no such file or directory './files/somefile.txt'
    at Object.openSync (fs.js:228:18)
    at Object.readFileSync (fs.js:119:15)
    at Object.<anonymous> (/home/user/dir/dir.js:4:16)
    at Module._compile (module.js:432:26)
    at Object..js (module.js:450:10)
    at Module.load (module.js:351:31)
    at Function._load (module.js:310:12)
    at Array.0 (module.js:470:10)
    at EventEmitter._tickCallback (node.js:192:40)

Using ./ worked with require but not for fs.readFileSync. That's because for fs.readFileSync, ./ translates into the cwd (in this case /home/user/). And /home/user/files/somefile.txt does not exist.

Check if DataRow exists by column name in c#?

You should try

if (row.Table.Columns.Contains("US_OTHERFRIEND"))

I don't believe that row has a columns property itself.

Service Temporarily Unavailable Magento?

If removing the flag shows service temporary unavailable. Go to "" and unisntall slider banner,BusinessDecision_Interaktingslider,lightbox2 and anotherone that I dont remember.

Is there a command to list all Unix group names?

To list all local groups which have users assigned to them, use this command:

cut -d: -f1 /etc/group | sort

For more info- > Unix groups, Cut command, sort command

How to set layout_weight attribute dynamically from code?

If the constructor with width, height and weight is not working, try using the constructor with width and height. And then manually set the weight.

And if you want the width to be set according to the weight, set width as 0 in the constructor. Same applies for height. Below code works for me.

LinearLayout.LayoutParams childParam1 = new LinearLayout.LayoutParams(0,LinearLayout.LayoutParams.MATCH_PARENT);
childParam1.weight = 0.3f;

LinearLayout.LayoutParams childParam2 = new LinearLayout.LayoutParams(0,LinearLayout.LayoutParams.MATCH_PARENT);
childParam2.weight = 0.7f;


html5 localStorage error with Safari: "QUOTA_EXCEEDED_ERR: DOM Exception 22: An attempt was made to add something to storage that exceeded the quota."

It seems that Safari 11 changes the behavior, and now local storage works in a private browser window. Hooray!

Our web app that used to fail in Safari private browsing now works flawlessly. It always worked fine in Chrome's private browsing mode, which has always allowed writing to local storage.

This is documented in Apple's Safari Technology Preview release notes - and the WebKit release notes - for release 29, which was in May 2017.


  • Fixed QuotaExceededError when saving to localStorage in private browsing mode or WebDriver sessions - r215315

Sorting a List<int>

Sort a list of integers descending

class Program
        private class SortIntDescending : IComparer<int>
            int IComparer<int>.Compare(int a, int b) //implement Compare
                if (a > b)
                    return -1; //normally greater than = 1
                if (a < b)
                    return 1; // normally smaller than = -1
                    return 0; // equal

        static List<int> intlist = new List<int>(); // make a list

        static void Main(string[] args)
            intlist.Add(5); //fill the list with 5 ints

            Console.WriteLine("Unsorted list :");

            // intlist.Sort(); uses the default Comparer, which is ascending
            intlist.Sort(new SortIntDescending()); //sort descending

            Console.WriteLine("Sorted descending list :");

            Console.ReadKey(); //wait for keydown

        static void Printlist(List<int> L)
            foreach (int i in L) //print on the console