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Some Of The Best Answers From Latest Asked Questions

Ripple effect on Android Lollipop CardView

The ripple effect was omitted in the appcompat support library which is what you're using. If you want to see the ripple use the Android L version and test it on an Android L device. Per the AppCompat v7 site:

"Why are there no ripples on pre-Lollipop? A lot of what allows RippleDrawable to run smoothly is Android 5.0’s new RenderThread. To optimize for performance on previous versions of Android, we've left RippleDrawable out for now."

Check out this link here for more info

importing go files in same folder

./main.go (in package main)
./a/a.go (in package a)
./a/b.go (in package a)

in this case:
main.go import "./a"

It can call the function in the a.go and b.go,that with first letter caps on.

Printing variables in Python 3.4

You can also format the string like so:

>>> print ("{index}. {word} appears {count} times".format(index=1, word='Hello', count=42))

Which outputs

1. Hello appears 42 times.

Because the values are named, their order does not matter. Making the example below output the same as the above example.

>>> print ("{index}. {word} appears {count} times".format(count=42, index=1, word='Hello'))

Formatting string this way allows you to do this.

>>> data = {'count':42, 'index':1, 'word':'Hello'}
>>> print ("{index}. {word} appears {count} times.".format(**data))
1. Hello appears 42 times.

Change Button color onClick

Using jquery, try this. if your button id is say id= clickme

$("clickme").on('çlick', function(){

$(this).css('background-color', 'grey'); .......

The superclass "javax.servlet.http.HttpServlet" was not found on the Java Build Path

For an Ant project:

Make sure, you have servlet-api.jar in the lib folder.

For a Maven project:

Make sure, you have the dependency added in POM.xml.


Another way to do it is: Update the project facets to pick up the right server.

Check this box in this location:

Project ? Properties ? Target Runtimes ? Apache Tomcat (any server)

How to remove unused dependencies from composer?

In fact, it is very easy.

composer update

will do all this for you, but it will also update the other packages.

To remove a package without updating the others, specifiy that package in the command, for instance:

composer update monolog/monolog

will remove the monolog/monolog package.

Nevertheless, there may remain some empty folders or files that cannot be removed automatically, and that have to be removed manually.

Using if-else in JSP

Instead of if-else condition use if in both conditions. it will work that way but not sure why.

No content to map due to end-of-input jackson parser

I had a similar error today and the issue was the content-type header of the post request. Make sure the content type is what you expect. In my case a multipart/form-data content-type header was being sent to the API instead of application/json.

indexOf and lastIndexOf in PHP?

This is the best way to do it, very simple.

$msg = "Hello this is a string";
$first_index_of_i = stripos($msg,'i');
$last_index_of_i = strripos($msg, 'i');

echo "First i : " . $first_index_of_i . PHP_EOL ."Last i : " . $last_index_of_i;

How to delete the last row of data of a pandas dataframe

Since index positioning in Python is 0-based, there won't actually be an element in index at the location corresponding to len(DF). You need that to be last_row = len(DF) - 1:

In [49]: dfrm
          A         B         C
0  0.120064  0.785538  0.465853
1  0.431655  0.436866  0.640136
2  0.445904  0.311565  0.934073
3  0.981609  0.695210  0.911697
4  0.008632  0.629269  0.226454
5  0.577577  0.467475  0.510031
6  0.580909  0.232846  0.271254
7  0.696596  0.362825  0.556433
8  0.738912  0.932779  0.029723
9  0.834706  0.002989  0.333436

[10 rows x 3 columns]

In [50]: dfrm.drop(dfrm.index[len(dfrm)-1])
          A         B         C
0  0.120064  0.785538  0.465853
1  0.431655  0.436866  0.640136
2  0.445904  0.311565  0.934073
3  0.981609  0.695210  0.911697
4  0.008632  0.629269  0.226454
5  0.577577  0.467475  0.510031
6  0.580909  0.232846  0.271254
7  0.696596  0.362825  0.556433
8  0.738912  0.932779  0.029723

[9 rows x 3 columns]

However, it's much simpler to just write DF[:-1].

TypeError: 'type' object is not subscriptable when indexing in to a dictionary

Normally Python throws NameError if the variable is not defined:

>>> d[0]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'd' is not defined

However, you've managed to stumble upon a name that already exists in Python.

Because dict is the name of a built-in type in Python you are seeing what appears to be a strange error message, but in reality it is not.

The type of dict is a type. All types are objects in Python. Thus you are actually trying to index into the type object. This is why the error message says that the "'type' object is not subscriptable."

>>> type(dict)
<type 'type'>
>>> dict[0]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'type' object is not subscriptable

Note that you can blindly assign to the dict name, but you really don't want to do that. It's just going to cause you problems later.

>>> dict = {1:'a'}
>>> type(dict)
<class 'dict'>
>>> dict[1]

The true source of the problem is that you must assign variables prior to trying to use them. If you simply reorder the statements of your question, it will almost certainly work:

d = {1: "walk1.png", 2: "walk2.png", 3: "walk3.png"}
m1 = pygame.image.load(d[1])
m2 = pygame.image.load(d[2])
m3 = pygame.image.load(d[3])
playerxy = (375,130)
window.blit(m1, (playerxy))

fatal error: mpi.h: No such file or directory #include <mpi.h>

As suggested above the inclusion of


in the include path takes care of this (in my case)

Using local makefile for CLion instead of CMake

Currently, only CMake is supported by CLion. Others build systems will be added in the future, but currently, you can only use CMake.

An importer tool has been implemented to help you to use CMake.


Source :

Check Postgres access for a user

You could query the table_privileges table in the information schema:

SELECT table_catalog, table_schema, table_name, privilege_type
FROM   information_schema.table_privileges 
WHERE  grantee = 'MY_USER'

How to join two tables by multiple columns in SQL?

You should only need to do a single join:

SELECT e.Grade, v.Score, e.CaseNum, e.FileNum, e.ActivityNum
FROM Evaluation e
INNER JOIN Value v ON e.CaseNum = v.CaseNum AND e.FileNum = v.FileNum AND e.ActivityNum = v.ActivityNum

DOM element to corresponding vue.js component

If you want listen an event (i.e OnClick) on an input with "demo" id, you can use:

new Vue({
  el: '#demo',
  data: {
    n: 0
  methods: {
   onClick: function (e) {
     console.log( // "A"
     console.log(e.targetVM === this) // true

What is ".NET Core"?

.NET Core is a free and open-source, managed computer software framework for Windows, Linux, and macOS operating systems. It is an open source, cross platform successor to .NET Framework.

.NET Core applications are supported on Windows, Linux, and macOS. In a nutshell .NET Core is similar to .NET framework, but it is cross-platform, i.e., it allows the .NET applications to run on Windows, Linux and MacOS. .NET framework applications can only run on the Windows system. So the basic difference between .NET framework and .NET core is that .NET Core is cross platform and .NET framework only runs on Windows.

Furthermore, .NET Core has built-in dependency injection by Microsoft and you do not have to use third-party software/DLL files for dependency injection.

How to get all key in JSON object (javascript)

Try this

var s = {name: "raul", age: "22", gender: "Male"}
   var keys = [];
   for(var k in s) keys.push(k);

Here keys array will return your keys ["name", "age", "gender"]

Python NLTK: SyntaxError: Non-ASCII character '\xc3' in file (Sentiment Analysis -NLP)

Add the following to the top of your file # coding=utf-8

If you go to the link in the error you can seen the reason why:

Defining the Encoding

Python will default to ASCII as standard encoding if no other encoding hints are given. To define a source code encoding, a magic comment must be placed into the source files either as first or second line in the file, such as: # coding=

UITableViewCell Selected Background Color on Multiple Selection

You can use standard UITableViewDelegate methods

- (nullable NSIndexPath *)tableView:(UITableView *)tableView willSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    EntityTableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];
    [cell selectMe];
    return indexPath;

- (nullable NSIndexPath *)tableView:(UITableView *)tableView willDeselectRowAtIndexPath:(NSIndexPath *)indexPath {
    EntityTableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];
    [cell deSelectMe];
    return indexPath;

in my situation this works, cause we need to select cell, change color, and when user taps 2 times on the selected cell further navigation should be performed.

Tomcat 8 throwing - org.apache.catalina.webresources.Cache.getResource Unable to add the resource

This isn’t a solution in the sense that it doesn’t resolve the conditions which cause the message to appear in the logs, but the message can be suppressed by appending the following to conf/

org.apache.catalina.webresources.Cache.level = SEVERE

This filters out the “Unable to add the resource” logs, which are at level WARNING.

In my view a WARNING is not necessarily an error that needs to be addressed, but rather can be ignored if desired.

phpmyadmin "Not Found" after install on Apache, Ubuntu

I had the same issue where these fixes didn't work.

I'm on Ubuntu 20.04 using hestiaCP with Nginx.

Today after adding

Include /etc/phpmyadmin/apache.conf

into both Apache and Nginx, Nginx failed to restart. It was having an issue with "proxy_buffers" value.

Yesterday I had to modify the Nginx config to add and increase these values so Magento 2.4 would run. Today I altered "proxy_buffers" again

proxy_buffers            3 64k;
proxy_buffer_size        128k;
proxy_busy_buffers_size  128k;

After the second alteration and the removal of "Include /etc/phpmyadmin/apache.conf" from both Apache and Nginx, Magento 2.4 and PHPMyAdmin are working as expected.

intellij incorrectly saying no beans of type found for autowired repository

Surprisingly, A Feign oriented project that successfully ran with Eclipse could not run in InteliJ. When started the application, InteliJ complained about the Feign client I tried to inject to the serviceImpl layer saying: field personRestClient (my Feign client) in ... required a bean of type ... that could not be found. Consider defining a bean of type '....' in your configuration.

I wasted a long time trying to understand what is wrong. I found a solution (for InteliJ) which I do not completely understand:

  1. Alt Shift F10 (or run menu)
  2. Select 'Edit configuration'
  3. In configuration window, Check the checkbox 'include dependencies with "Provided" scope'
  4. Run your application

Or choose Eclipse :)

pandas create new column based on values from other columns / apply a function of multiple columns, row-wise

.apply() takes in a function as the first parameter; pass in the label_race function as so:

df['race_label'] = df.apply(label_race, axis=1)

You don't need to make a lambda function to pass in a function.

How to stash my previous commit?

An alternative solution uses the stash:


~/dev/gitpro $git stash list

~/dev/gitpro $git log --oneline -3

* 7049dd5 (HEAD -> master) c111
* 3f1fa3d c222
* 0a0f6c4 c333
  1. git reset head~1 <--- head shifted one back to c222; working still contains c111 changes
  2. git stash push -m "commit 111" <--- staging/working (containing c111 changes) stashed; staging/working rolled back to revised head (containing c222 changes)
  3. git reset head~1 <--- head shifted one back to c333; working still contains c222 changes
  4. git stash push -m "commit 222" <--- staging/working (containing c222 changes) stashed; staging/working rolled back to revised head (containing c333 changes)
  5. git stash pop stash@{1} <--- oldest stash entry with c111 changes removed & applied to staging/working
  6. git commit -am "commit 111" <-- new commit with c111's changes becomes new head

note you cannot run 'git stash pop' without specifying the stash@{1} entry. The stash is a LIFO stack -- not FIFO -- so that would incorrectly pop the stash@{0} entry with c222's changes (instead of stash@{1} with c111's changes).

note if there are conflicting chunks between commits 111 and 222, then you'll be forced to resolve them when attempting to pop. (This would be the case if you went with an alternative rebase solution as well.)


~/dev/gitpro $git stash list

stash@{0}: On master: c222

~/dev/gitpro $git log -2 --oneline

* edbd9e8 (HEAD -> master) c111
* 0a0f6c4 c333

Tomcat 8 Maven Plugin for Java 8

Since November 2017, one can use tomcat8-maven-plugin:

<!-- -->

Note that this plugin resides in ICM repo (not in Maven Central), hence you should add the repo to your pluginsRepositories in your pom.xml:

        <name>Spring Framework Milestone Repository</name>

An unhandled exception occurred during the execution of the current web request. ASP.NET

I had the same problem and found out that I had forgotten to include the script in the file which I want to include in the live site.

Also, you should try this:

bundles.Add(new ScriptBundle("~/bundles/jquery").Include(

React.js inline style best practices

I prefer to use styled-components. It provide better solution for design.

import React, { Component, Fragment } from 'react'
import styled from 'styled-components';

const StyledDiv = styled.div`
    display: block;
    margin-left: auto;
    margin-right: auto;
    font-size:200; // here we can set static
    color: ${props => props.color} // set dynamic color by props

export default class RenderHtml extends Component {
    render() {
        return (
                <StyledDiv color={'white'}>
                    Have a good and productive day!

Unable to get spring boot to automatically create database schema

The configurations below worked for me:

Find duplicate records in MongoDB

    {$group: { 
            _id: {name: "$name"},
            uniqueIds: {$addToSet: "$_id"},
            count: {$sum: 1}
    {$match: { 
        count: {"$gt": 1}

First Group Query the group according to the fields.

Then we check the unique Id and count it, If count is greater then 1 then the field is duplicate in the entire collection so that thing is to be handle by $match query.

Efficiently sorting a numpy array in descending order?

For short arrays I suggest using np.argsort() by finding the indices of the sorted negatived array, which is slightly faster than reversing the sorted array:

In [37]: temp = np.random.randint(1,10, 10)

In [38]: %timeit np.sort(temp)[::-1]
100000 loops, best of 3: 4.65 µs per loop

In [39]: %timeit temp[np.argsort(-temp)]
100000 loops, best of 3: 3.91 µs per loop

AngularJS - Does $destroy remove event listeners?

Event listeners

First off it's important to understand that there are two kinds of "event listeners":

  1. Scope event listeners registered via $on:

    $scope.$on('anEvent', function (event, data) {
  2. Event handlers attached to elements via for example on or bind:

    element.on('click', function (event) {


When $scope.$destroy() is executed it will remove all listeners registered via $on on that $scope.

It will not remove DOM elements or any attached event handlers of the second kind.

This means that calling $scope.$destroy() manually from example within a directive's link function will not remove a handler attached via for example element.on, nor the DOM element itself.


Note that remove is a jqLite method (or a jQuery method if jQuery is loaded before AngularjS) and is not available on a standard DOM Element Object.

When element.remove() is executed that element and all of its children will be removed from the DOM together will all event handlers attached via for example element.on.

It will not destroy the $scope associated with the element.

To make it more confusing there is also a jQuery event called $destroy. Sometimes when working with third-party jQuery libraries that remove elements, or if you remove them manually, you might need to perform clean up when that happens:

element.on('$destroy', function () {

What to do when a directive is "destroyed"

This depends on how the directive is "destroyed".

A normal case is that a directive is destroyed because ng-view changes the current view. When this happens the ng-view directive will destroy the associated $scope, sever all the references to its parent scope and call remove() on the element.

This means that if that view contains a directive with this in its link function when it's destroyed by ng-view:

scope.$on('anEvent', function () {

element.on('click', function () {

Both event listeners will be removed automatically.

However, it's important to note that the code inside these listeners can still cause memory leaks, for example if you have achieved the common JS memory leak pattern circular references.

Even in this normal case of a directive getting destroyed due to a view changing there are things you might need to manually clean up.

For example if you have registered a listener on $rootScope:

var unregisterFn = $rootScope.$on('anEvent', function () {});

scope.$on('$destroy', unregisterFn);

This is needed since $rootScope is never destroyed during the lifetime of the application.

The same goes if you are using another pub/sub implementation that doesn't automatically perform the necessary cleanup when the $scope is destroyed, or if your directive passes callbacks to services.

Another situation would be to cancel $interval/$timeout:

var promise = $interval(function () {}, 1000);

scope.$on('$destroy', function () {

If your directive attaches event handlers to elements for example outside the current view, you need to manually clean those up as well:

var windowClick = function () {

angular.element(window).on('click', windowClick);

scope.$on('$destroy', function () {
  angular.element(window).off('click', windowClick);

These were some examples of what to do when directives are "destroyed" by Angular, for example by ng-view or ng-if.

If you have custom directives that manage the lifecycle of DOM elements etc. it will of course get more complex.

ps command doesn't work in docker container

use docker top

docker top <container ID>

MySQL Insert with While Loop

You cannot use WHILE like that; see: mysql DECLARE WHILE outside stored procedure how?

You have to put your code in a stored procedure. Example:

    DECLARE i int DEFAULT 237692001;
    WHILE i <= 237692004 DO
        INSERT INTO mytable (code, active, total) VALUES (i, 1, 1);
        SET i = i + 1;


Alternatively, generate a list of INSERT statements using any programming language you like; for a one-time creation, it should be fine. As an example, here's a Bash one-liner:

for i in {2376921001..2376921099}; do echo "INSERT INTO mytable (code, active, total) VALUES ($i, 1, 1);"; done

By the way, you made a typo in your numbers; 2376921001 has 10 digits, 237692200 only 9.

Solve Cross Origin Resource Sharing with Flask

I might be a late on this question but below steps fixed the issue

from flask import Flask
from flask_cors import CORS

app = Flask(__name__)

Powershell: count members of a AD group

In Powershell, you'll need to import the active directory module, then use the get-adgroupmember, and then measure-object. For example, to get the number of users belonging to the group "domain users", do the following:

Import-Module activedirecotry
Get-ADGroupMember "domain users" | Measure-Object

When entering the group name after "Get-ADGroupMember", if the name is a single string with no spaces, then no quotes are necessary. If the group name has spaces in it, use the quotes around it.

The output will look something like:

Count    : 12345
Average  :
Sum      :
Maximum  :
Minimum  :
Property :

Note - importing the active directory module may be redundant if you're already using PowerShell for other AD admin tasks.

pandas unique values multiple columns

In [5]: set(df.Col1).union(set(df.Col2))
Out[5]: {'Bill', 'Bob', 'Joe', 'Mary', 'Steve'}


set(df.Col1) | set(df.Col2)

What is <scope> under <dependency> in pom.xml for?

The <scope> element can take 6 values: compile, provided, runtime, test, system and import.

This scope is used to limit the transitivity of a dependency, and also to affect the classpath used for various build tasks.


This is the default scope, used if none is specified. Compile dependencies are available in all classpaths of a project. Furthermore, those dependencies are propagated to dependent projects.


This is much like compile, but indicates you expect the JDK or a container to provide the dependency at runtime. For example, when building a web application for the Java Enterprise Edition, you would set the dependency on the Servlet API and related Java EE APIs to scope provided because the web container provides those classes. This scope is only available on the compilation and test classpath, and is not transitive.


This scope indicates that the dependency is not required for compilation, but is for execution. It is in the runtime and test classpaths, but not the compile classpath.


This scope indicates that the dependency is not required for normal use of the application, and is only available for the test compilation and execution phases.


This scope is similar to provided except that you have to provide the JAR which contains it explicitly. The artifact is always available and is not looked up in a repository.

import (only available in Maven 2.0.9 or later)

This scope is only used on a dependency of type pom in the section. It indicates that the specified POM should be replaced with the dependencies in that POM's section. Since they are replaced, dependencies with a scope of import do not actually participate in limiting the transitivity of a dependency.

To answer the second part of your question:

How can we use it for running test?

Note that the test scope allows to use dependencies only for the test phase.

Read the documentation for full details.

Setting a max character length in CSS

With Chrome you can set the number of lines displayed with "-webkit-line-clamp" :

     display: -webkit-box;
    -webkit-box-orient: vertical;
    -webkit-line-clamp: 3;  /* Number of lines displayed before it truncate */
     overflow: hidden;

So for me it is to use in an extension so it is perfect, more information here:

How do I setup the dotenv file in Node.js?

Make sure to set cwd in the pm2 config to the correct directory for any calls to dotenv.config().

Example: Your index.js file is in /app/src, your .env file is in /app. Your index.js file has this

dotenv.config({path: "../.env"});

Your pm2 json config should have this: "cwd": "/app/src", "script": "index.js"

You could also use dotenv.config({path: path.join(__dirname, "../.env")}); to avoid the CWD issue. You will still have a problem if you move the .env or the index.js file relative to each other.

How to set Toolbar text and back arrow color

Try this on your XML file

        app:popupTheme="@style/AppTheme.PopupOverlay" />

And add this is your colors.xml file

    <color name="colorAccent">YOUR_COLOR</color> duplicate entry during packageAllDebugClassesForMultiDex

You need to check that you have inserted v4 library and compile library? You must not repeat library in your app or your dependence program.

delete the repeat library so that just one V4 remains.

in your app dir build.gradle file add this command:


    configurations {
        all*.exclude group: '', module: 'support-v4'
        all*.exclude group: '', module: 'support-annotations'


it works for me! You can try it!

Multipart File Upload Using Spring Rest Template + Spring Web MVC

Here are my working example

@RequestMapping(value = "/api/v1/files/upload", method =RequestMethod.POST)
public ResponseEntity<?> upload(@RequestParam("files") MultipartFile[] files) {
    LinkedMultiValueMap<String, Object> map = new LinkedMultiValueMap<>();
    List<String> tempFileNames = new ArrayList<>();
    String tempFileName;
    FileOutputStream fo;

    try {
        for (MultipartFile file : files) {
            tempFileName = "/tmp/" + file.getOriginalFilename();
            fo = new FileOutputStream(tempFileName);
            map.add("files", new FileSystemResource(tempFileName));

        HttpHeaders headers = new HttpHeaders();

        HttpEntity<LinkedMultiValueMap<String, Object>> requestEntity = new HttpEntity<>(map, headers);
        String response = restTemplate.postForObject(uploadFilesUrl, requestEntity, String.class);

    } catch (IOException e) {

    for (String fileName : tempFileNames) {
        File f = new File(fileName);
    return new ResponseEntity<Object>(HttpStatus.OK);

How to create a floating action button (FAB) in android, using AppCompat v21?

Try this library, it supports shadow, there is minSdkVersion=7 and also supports android:elevation attribute for API-21 implicitly.

Original post is here.

How can I make a button have a rounded border in Swift?

To do this job in storyboard (Interface Builder Inspector)

With help of IBDesignable, we can add more options to Interface Builder Inspector for UIButton and tweak them on storyboard. First, add the following code to your project.

@IBDesignable extension UIButton {

    @IBInspectable var borderWidth: CGFloat {
        set {
            layer.borderWidth = newValue
        get {
            return layer.borderWidth

    @IBInspectable var cornerRadius: CGFloat {
        set {
            layer.cornerRadius = newValue
        get {
            return layer.cornerRadius

    @IBInspectable var borderColor: UIColor? {
        set {
            guard let uiColor = newValue else { return }
            layer.borderColor = uiColor.cgColor
        get {
            guard let color = layer.borderColor else { return nil }
            return UIColor(cgColor: color)

Then simply set the attributes for buttons on storyboard.

enter image description here

How to change the color of header bar and address bar in newest Chrome version on Lollipop?

For example, to set the background to your favorite/Branding color

Add Below Meta property to your HTML code in HEAD Section

  <meta name="theme-color" content="Your Hexadecimal Code">


  <meta name="theme-color" content="#444444">

In Below Image, I just mentioned How Chrome taken your theme-color Property

enter image description here

Firefox OS, Safari, Internet Explorer and Opera Coast allow you to define colors for elements of the browser, and even the platform using meta tags.

<!-- Windows Phone -->
<meta name="msapplication-navbutton-color" content="#4285f4">
<!-- iOS Safari -->
<meta name="apple-mobile-web-app-capable" content="yes">
<meta name="apple-mobile-web-app-status-bar-style" content="black-translucent">

Safari specific styling

From the guidelinesDocuments Here

Hiding Safari User Interface Components

Set the apple-mobile-web-app-capable meta tag to yes to turn on standalone mode. For example, the following HTML displays web content using standalone mode.

<meta name="apple-mobile-web-app-capable" content="yes">

Changing the Status Bar Appearance

You can change the appearance of the default status bar to either black or black-translucent. With black-translucent, the status bar floats on top of the full screen content, rather than pushing it down. This gives the layout more height, but obstructs the top. Here’s the code required:

<meta name="apple-mobile-web-app-status-bar-style" content="black">

For more on status bar appearance, see apple-mobile-web-app-status-bar-style.

For Example:

Screenshot using black-translucent

Screenshot using black-translucent

Screenshot using black

Screenshot using black

Convert Java object to XML string

To convert an Object to XML in Java

package com;

import java.util.ArrayList;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;

* @author ABsiddik

public class Customer {

int id;
String name;
int age;

String address;
ArrayList<String> mobileNo;

 public int getId() {
    return id;

public void setId(int id) { = id;

public String getName() {
    return name;

public void setName(String name) { = name;

public int getAge() {
    return age;

public void setAge(int age) {
    this.age = age;

public String getAddress() {
    return address;

public void setAddress(String address) {
    this.address = address;

public ArrayList<String> getMobileNo() {
    return mobileNo;

public void setMobileNo(ArrayList<String> mobileNo) {
    this.mobileNo = mobileNo;


package com;

import java.util.ArrayList;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.Marshaller;

* @author ABsiddik
public class ConvertObjToXML {

public static void main(String args[]) throws Exception
    ArrayList<String> numberList = new ArrayList<>();

    Customer c = new Customer();

    c.setName("Abu Bakar Siddik");
    c.setAddress("Dhaka, Bangladesh");

    File file = new File("C:\\Users\\NETIZEN-ONE\\Desktop \\customer.xml");
    JAXBContext jaxbContext = JAXBContext.newInstance(Customer.class);
    Marshaller jaxbMarshaller = jaxbContext.createMarshaller();
    jaxbMarshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);

    jaxbMarshaller.marshal(c, file);// this line create customer.xml file in specified path.

    StringWriter sw = new StringWriter();
    jaxbMarshaller.marshal(c, sw);
    String xmlString = sw.toString();



Try with this example..

Why is my Button text forced to ALL CAPS on Lollipop?

If you have arrived here because your facebook button text appears in all caps then just add this android:textAllCaps="false" in your xml file. It worked for me.

Edit existing excel workbooks and sheets with xlrd and xlwt

As I wrote in the edits of the op, to edit existing excel documents you must use the xlutils module (Thanks Oliver)

Here is the proper way to do it:

#xlrd, xlutils and xlwt modules need to be installed.  
#Can be done via pip install <module>
from xlrd import open_workbook
from xlutils.copy import copy

rb = open_workbook("names.xls")
wb = copy(rb)

s = wb.get_sheet(0)

This replaces the contents of the cell located at a1 in the first sheet of "names.xls" with the text "a1", and then saves the document.

How to add 'libs' folder in Android Studio?

Click the left side dropdown menu "android" and choose "project" to see libs folders

enter image description here

*after choosing project you will see the libs directory

Changing the Status Bar Color for specific ViewControllers using Swift in iOS8

Swift 3

In your AppDelegate file inside func application method

let statusBar: UIView = application.value(forKey: "statusBar") as! UIView
statusBar.backgroundColor = .red

Intellij Cannot resolve symbol on import

I found the following answer from @jossef-harush and @matt-leidholm useful from another link

  • in IntelliJ editor, click on the red keyword (Integer for example) and press ALT + ENTER (or click the light bulb icon)
  • select Setup JDK from the intentions menu

IntelliJ intentions menu

  • click on Configure

Project SDK selection dialog

  • In my case, the JDK path was incorrect (pointed on /opt/jdk1.7.0_51 instead of /opt/jdk1.7.0_65)

Broken Configure SDK dialog

  • click on the ... and browse to the right JDK path

Fixed Configure SDK dialog

  • let's clear the cache

IntelliJ File menu

Laravel Checking If a Record Exists

The Easiest Way to do

    public function update(Request $request, $id)

    $coupon = Coupon::where('name','=',$request->name)->first(); 

    if($coupon->id != $id){
        $validatedData = $request->validate([
            'discount' => 'required',   
            'name' => 'required|unique:coupons|max:255',      

    $requestData = $request->all();
    $coupon = Coupon::findOrFail($id);
    return redirect('admin/coupons')->with('flash_message', 'Coupon updated!');

How do I use tools:overrideLibrary in a build.gradle file?

Open Android Studio -> Open Manifest File

add <uses-sdk tools:overrideLibrary=""/> don't forget to include xmlns:tools="" too, before the <application> tag

enter image description here

How to run Gradle from the command line on Mac bash

Also, if you don't have the gradlew file in your current directory:

You can install gradle with homebrew with the following command:

$ brew install gradle

As mentioned in this answer. Then, you are not going to need to include it in your path (homebrew will take care of that) and you can just run (from any directory):

$ gradle test 

How to enable C# 6.0 feature in Visual Studio 2013?

Information for obsoleted prerelease software:

According to this it's just a install and go for Visual Studio 2013:

In fact, installing the C# 6.0 compiler from this release involves little more than installing a Visual Studio 2013 extension, which in turn updates the MSBuild target files.

So just get the files from and you are ready to go.

You do have to know it is an outdated version of the specs implemented there, since they no longer update the package for Visual Studio 2013:

You can also try April's End User Preview, which installs on top of Visual Studio 2013. (note: this VS 2013 preview is quite out of date, and is no longer updated)

So if you do want to use the latest version, you have to download the Visual Studio 2015.

In a Dockerfile, How to update PATH environment variable?

You can use Environment Replacement in your Dockerfile as follows:

ENV PATH="/opt/gtk/bin:${PATH}"

How to change status bar color to match app in Lollipop? [Android]

To set the status bar color, create a style.xml file under res/values-v21 folder with this content:

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

    <style name="AppBaseTheme" parent="AppTheme">
        <item name="android:windowDrawsSystemBarBackgrounds">true</item>
        <item name="android:statusBarColor">@color/blue</item>


UnicodeEncodeError: 'charmap' codec can't encode characters

I was getting the same UnicodeEncodeError when saving scraped web content to a file. To fix it I replaced this code:

with open(fname, "w") as f:

with this:

import io
with, "w", encoding="utf-8") as f:

Using io gives you backward compatibility with Python 2.

If you only need to support Python 3 you can use the builtin open function instead:

with open(fname, "w", encoding="utf-8") as f:

Unable to add window -- token null is not valid; is your activity running?

I was getting this error while trying to show DatePicker from Fragment.

I changed

val datePickerDialog = DatePickerDialog(activity!!.applicationContext, ...)


val datePickerDialog = DatePickerDialog(requireContext(), ...)

and it worked just fine.

Write-back vs Write-Through caching?

Write-Back is a more complex one and requires a complicated Cache Coherence Protocol(MOESI) but it is worth it as it makes the system fast and efficient.

The only benefit of Write-Through is that it makes the implementation extremely simple and no complicated cache coherency protocol is required.

How to resolve "git pull,fatal: unable to access '\': Empty reply from server"

I received the same error in pushing files to my private bitbucket repository. For some odd reasons, the request couldn't be sent and an empty reply was the result! I tried again with a proxy tunnel (you can use any other VPN applications) and it has been solved till now.

Android check null or empty string in Android

Use TextUtils.isEmpty( someString )

String myString = null;

if (TextUtils.isEmpty(myString)) {
    return; // or break, continue, throw

// myString is neither null nor empty if this point is reached
Log.i("TAG", myString);


  • The documentation states that both null and zero length are checked for. No need to reinvent the wheel here.
  • A good practice to follow is early return.

RecyclerView inside ScrollView is not working

You can use this way either :

Add this line to your recyclerView xml view :


try it ,recyclerview will be smoothly scrolled with flexible height

hope this helped .

ggplot2 line chart gives "geom_path: Each group consist of only one observation. Do you need to adjust the group aesthetic?"

Start up R in a fresh session and paste this in:


df <- structure(list(year = c(1, 2, 3, 4), pollution = structure(c(346.82, 
134.308821199349, 130.430379885892, 88.275457392443), .Dim = 4L, .Dimnames = list(
    c("1999", "2002", "2005", "2008")))), .Names = c("year", 
"pollution"), row.names = c(NA, -4L), class = "data.frame")

df[] <- lapply(df, as.numeric) # make all columns numeric

ggplot(df, aes(year, pollution)) +
           geom_point() +
           geom_line() +
           labs(x = "Year", 
                y = "Particulate matter emissions (tons)", 
                title = "Motor vehicle emissions in Baltimore")

Error: Failed to execute 'appendChild' on 'Node': parameter 1 is not of type 'Node'

It's actually a simple answer.

Your function is returning a string rather than the div node. appendChild can only append a node.

For example, if you try to appendChild the string:

var z = '<p>test satu dua tiga</p>'; // is a string 

The above code will never work. What will work is:

var z = document.createElement('p'); // is a node
z.innerHTML = 'test satu dua tiga';

Gradle DSL method not found: 'runProguard'

runProguard has been renamed to minifyEnabled in version 0.14.0 (2014/10/31) or more in Gradle.

To fix this, you need to change runProguard to minifyEnabled in the build.gradle file of your project.

enter image description here

Warning: #1265 Data truncated for column 'pdd' at row 1

As the message error says, you need to Increase the length of your column to fit the length of the data you are trying to insert (0000-00-00)


Following your comment, I run a test table:

mysql> create table testDate(id int(2) not null auto_increment, pdd date default null, primary key(id));
Query OK, 0 rows affected (0.20 sec)


mysql> insert into testDate values(1,'0000-00-00');
Query OK, 1 row affected (0.06 sec)


So, aparently you want to insert a NULL value to pdd field as your comment states ? You can do that in 2 ways like this:

Method 1:

mysql> insert into testDate values(2,'');
Query OK, 1 row affected, 1 warning (0.06 sec)

Method 2:

mysql> insert into testDate values(3,NULL);
Query OK, 1 row affected (0.07 sec)


You failed to change the default value of pdd field. Here is the syntax how to do it (in my case, I set it to NULL in the start, now I will change it to NOT NULL)

mysql> alter table testDate modify pdd date not null;
Query OK, 3 rows affected, 1 warning (0.60 sec)
Records: 3  Duplicates: 0  Warnings: 1

How to remove all files from directory without removing directory in Node.js

To remove all files from a directory, first you need to list all files in the directory using fs.readdir, then you can use fs.unlink to remove each file. Also fs.readdir will give just the file names, you need to concat with the directory name to get the full path.

Here is an example

const fs = require('fs');
const path = require('path');

const directory = 'test';

fs.readdir(directory, (err, files) => {
  if (err) throw err;

  for (const file of files) {
    fs.unlink(path.join(directory, file), err => {
      if (err) throw err;

Update node version 14

There is a recursive flag that you can use in rmdir to remove all the files recursively. See nodejs docs for more information.

const fs = require('fs').promises;

const directory = 'test';

fs.rmdir(directory, { recursive: true })
  .then(() => console.log('directory removed!'));

AES Encrypt and Decrypt

Code provided by SHS didn't work for me, but this one apparently did (I used a Bridging Header: #import <CommonCrypto/CommonCrypto.h>):

extension String {

    func aesEncrypt(key:String, iv:String, options:Int = kCCOptionPKCS7Padding) -> String? {
        if let keyData = String.Encoding.utf8),
            let data = String.Encoding.utf8),
            let cryptData    = NSMutableData(length: Int((data.count)) + kCCBlockSizeAES128) {

            let keyLength              = size_t(kCCKeySizeAES128)
            let operation: CCOperation = UInt32(kCCEncrypt)
            let algoritm:  CCAlgorithm = UInt32(kCCAlgorithmAES128)
            let options:   CCOptions   = UInt32(options)

            var numBytesEncrypted :size_t = 0

            let cryptStatus = CCCrypt(operation,
                                      (keyData as NSData).bytes, keyLength,
                                      (data as NSData).bytes, data.count,
                                      cryptData.mutableBytes, cryptData.length,

            if UInt32(cryptStatus) == UInt32(kCCSuccess) {
                cryptData.length = Int(numBytesEncrypted)
                let base64cryptString = cryptData.base64EncodedString(options: .lineLength64Characters)
                return base64cryptString

            else {
                return nil
        return nil

    func aesDecrypt(key:String, iv:String, options:Int = kCCOptionPKCS7Padding) -> String? {
        if let keyData = String.Encoding.utf8),
            let data = NSData(base64Encoded: self, options: .ignoreUnknownCharacters),
            let cryptData    = NSMutableData(length: Int((data.length)) + kCCBlockSizeAES128) {

            let keyLength              = size_t(kCCKeySizeAES128)
            let operation: CCOperation = UInt32(kCCDecrypt)
            let algoritm:  CCAlgorithm = UInt32(kCCAlgorithmAES128)
            let options:   CCOptions   = UInt32(options)

            var numBytesEncrypted :size_t = 0

            let cryptStatus = CCCrypt(operation,
                                      (keyData as NSData).bytes, keyLength,
                                      data.bytes, data.length,
                                      cryptData.mutableBytes, cryptData.length,

            if UInt32(cryptStatus) == UInt32(kCCSuccess) {
                cryptData.length = Int(numBytesEncrypted)
                let unencryptedMessage = String(data: cryptData as Data, encoding:String.Encoding.utf8)
                return unencryptedMessage
            else {
                return nil
        return nil


From my ViewController:

 let encoded = message.aesEncrypt(key: keyString, iv: iv)
 let unencode = encoded?.aesDecrypt(key: keyString, iv: iv)

Groovy: How to check if a string contains any element of an array?

def valid = pointAddress.findAll { a ->
    validPointTypes.any { a.contains(it) }

Should do it

How to include files outside of Docker's build context?

On Linux you can mount other directories instead of symlinking them

mount --bind olddir newdir

See for more details.

I don't know if something similar is available for other OSes. I also tried using Samba to share a folder and remount it into the Docker context which worked as well.

User Get-ADUser to list all properties and export to .csv

This can be simplified by completely skipping the where object and the $users declaration. All you need is:


get-content c:\scripts\users.txt | get-aduser -properties * | select displayname, office | export-csv c:\path\to\your.csv

Add newline to VBA or Visual Basic 6

Visual Basic has built-in constants for newlines:

vbCr = Chr$(13) = CR (carriage-return character) - used by Mac OS and Apple II family

vbLf = Chr$(10) = LF (line-feed character) - used by Linux and Mac OS X

vbCrLf = Chr$(13) & Chr$(10) = CRLF (carriage-return followed by line-feed) - used by Windows

vbNewLine = the same as vbCrLf

Scraping data from website using vba

I modified some thing that were poping up error for me and end up with this which worked great to extract the data as I needed:

Sub get_data_web()

Dim appIE As Object
Set appIE = CreateObject("internetexplorer.application")

With appIE
    .navigate ""
    .Visible = True
End With

Do While appIE.Busy

Set allRowofData = appIE.document.getElementsByClassName("Ta(end) BdT Bdc($c-fuji-grey-c) H(36px)")

Dim i As Long
Dim myValue As String

Count = 1

    For Each itm In allRowofData

        For i = 0 To 4

        myValue = itm.Cells(i).innerText
        ActiveSheet.Cells(Count, i + 1).Value = myValue


        Count = Count + 1


Set appIE = Nothing

End Sub

Meaning of .Cells(.Rows.Count,"A").End(xlUp).row


I think the first dot in the parenthesis should not be there, I mean, you should write it in this way:


Before the Cells, you can write your worksheet name, for example:

Worksheets("sheet1").Cells(Rows.Count, 2).End(xlUp).row

The worksheet name is not necessary when you operate on the same worksheet.

TypeError: $(...).modal is not a function with bootstrap Modal

For me, I had //= require jquery after //= require bootstrap. Once I moved jquery before bootstrap, everything worked.

How to run PyCharm in Ubuntu - "Run in Terminal" or "Run"?

As mentioned in the above answer, by updating the bashrc file you can run the from anywhere on the linux terminal.

But if you love the icon and wants the Desktop shortcuts for the Pycharm on Ubuntu OS then follow the Below steps,

 Quick way to create Pycharm launcher. 
     1. Start Pycharm using the cmd from anywhere on the terminal or start the located under bin folder of the pycharm artifact.
     2. Once the Pycharm application loads, navigate to tools menu and select “Create Desktop Entry..”
     3. Check the box if you want the launcher for all users.
     4. If you Check the box i.e “Create entry for all users”, you will be asked for your password.
     5. A message should appear informing you that it was successful.
     6. Now Restart Pycharm application and you will find Pycharm in Unity dash and Application launcher.."

Converting URL to String and back again

fileURLWithPath() is used to convert a plain file path (e.g. "/path/to/file") to an URL. Your urlString is a full URL string including the scheme, so you should use

let url = NSURL(string: urlstring)

to convert it back to NSURL. Example:

let urlstring = "file:///Users/Me/Desktop/Doc.txt"
let url = NSURL(string: urlstring)
println("the url = \(url!)")
// the url = file:///Users/Me/Desktop/Doc.txt

Replacing few values in a pandas dataframe column with another value

Created the Data frame:

import pandas as pd

Now use DataFrame.replace() function:


Format cell if cell contains date less than today

Your first problem was you weren't using your compare symbols correctly.

< less than
> greater than
<= less than or equal to
>= greater than or equal to

To answer your other questions; get the condition to work on every cell in the column and what about blanks?

What about blanks?

Add an extra IF condition to check if the cell is blank or not, if it isn't blank perform the check. =IF(B2="","",B2<=TODAY())

Condition on every cell in column

enter image description here

Run a controller function whenever a view is opened/shown

This is probably what you were looking for:

Ionic caches your views and thus your controllers by default (max of 10)

There are events you can hook onto to let your controller do certain things based on those ionic events. see here for an example:

How to fix symbol lookup error: undefined symbol errors in a cluster environment

After two dozens of comments to understand the situation, it was found that the was actually a symlink (with several levels of indirection) to a file that was not shared between the queued processes and the interactive processes. This means even though the symlink itself lies on a shared filesystem, the contents of the file do not and as a result the process was seeing different versions of the library.

For future reference: other than checking LD_LIBRARY_PATH, it's always a good idea to check a library with nm -D to see if the symbols actually exist. In this case it was found that they do exist in interactive mode but not when run in the queue. A quick md5sum revealed that the files were actually different.

How to get a user's time zone?

func getCurrentTimeZone() -> String {
        let localTimeZoneAbbreviation: Int = TimeZone.current.secondsFromGMT()
        let gmtAbbreviation = (localTimeZoneAbbreviation / 60)
        return "\(gmtAbbreviation)"

You can get current time zone abbreviation.

How to set a background image in Xcode using swift?

Swift 5.3 in XCode 12.2 Playgrounds

Place the cursor wherever in the code the #insertLiteral would have been in earlier versions. Select from the top-menu Editor->Insert Image Literal... and navigate to the file. Click Open.

The file is added to a playground Resource folder and will then appear when the playground is run in whichever view it was positioned when selected.

If a file is already in the playground Bundle, e.g. in /Resources, it can be dragged directly to the required position in the code (where it will be represented by an icon).

cf. Apple help docs give details of this and how to place other colour and file literals.


replace below lines:

<permission android:name="com.myapp.permission.C2D_MESSAGE" android:protectionLevel="signature" />
<uses-permission android:name="com.myapp.permission.C2D_MESSAGE" 
android:protectionLevel="signature" /> 

Convert a String to int?

So basically you want to convert a String into an Integer right! here is what I mostly use and that is also mentioned in official documentation..

fn main() {

    let char = "23";
    let char : i32 = char.trim().parse().unwrap();
    println!("{}", char + 1);


This works for both String and &str Hope this will help too.

Jmeter - get current date and time

Actually, for UTC I used Z instead of X, e.g.


which gave me:


How can I verify if an AD account is locked?

If you want to check via command line , then use command "net user username /DOMAIN"

enter image description here

How to check if a scope variable is undefined in AngularJS template?

If you're using Angular 1, I would recommend using Angular's built-in method:


reference :

How to resolve "gpg: command not found" error during RVM installation?

On Mac OSX 10.15, Even after installing gpg, i was getting gpg2 command not found

$ brew install gnupg gnupg2
Warning: gnupg 2.2.23 is already installed and up-to-date
To reinstall 2.2.23, run `brew reinstall gnupg`

$ gpg2 --recv-keys 409B6B1796C275462A1703113804BB82D39DC0E3 7D2BAF1CF37B13E2069D6956105BD0E739499BDB
-bash: gpg2: command not found

Instead, this worked for me

$ gpg --keyserver hkp:// --recv-keys 409B6B1796C275462A1703113804BB82D39DC0E3 7D2BAF1CF37B13E2069D6956105BD0E739499BDB

NSRange from Swift Range?

Swift 4:

Sure, I know that Swift 4 has an extension for NSRange already

public init<R, S>(_ region: R, in target: S) where R : RangeExpression,
    S : StringProtocol, 
    R.Bound == String.Index, S.Index == String.Index

I know in most cases this init is enough. See its usage:

let string = "Many animals here:  !!!"

if let range = string.range(of: ""){
     print((string as NSString).substring(with: NSRange(range, in: string))) //  ""

But conversion can be done directly from Range< String.Index > to NSRange without Swift's String instance.

Instead of generic init usage which requires from you the target parameter as String and if you don't have target string at hand you can create conversion directly

extension NSRange {
    public init(_ range:Range<String.Index>) {
        self.init(location: range.lowerBound.encodedOffset,
              length: range.upperBound.encodedOffset -
                      range.lowerBound.encodedOffset) }

or you can create the specialized extension for Range itself

extension Range where Bound == String.Index {
    var nsRange:NSRange {
    return NSRange(location: self.lowerBound.encodedOffset,
                     length: self.upperBound.encodedOffset -


let string = "Many animals here:  !!!"
if let range = string.range(of: ""){
    print((string as NSString).substring(with: NSRange(range))) //  ""


if let nsrange = string.range(of: "")?.nsRange{
    print((string as NSString).substring(with: nsrange)) //  ""

Swift 5:

Due to the migration of Swift strings to UTF-8 encoding by default, the usage of encodedOffset is considered as deprecated and Range cannot be converted to NSRange without an instance of String itself, because in order to calculate the offset we need the source string which is encoded in UTF-8 and it should be converted to UTF-16 before calculating offset. So best approach, for now, is to use generic init.

Programmatically set image to UIImageView with Xcode 6.1/Swift

Since you have your bgImage assigned and linked as an IBOutlet, there is no need to initialize it as a UIImageView... instead all you need to do is set the image property like bgImage.image = UIImage(named: "afternoon"). After running this code, the image appeared fine since it was already assigned using the outlet.

enter image description here

However, if it wasn't an outlet and you didn't have it already connected to a UIImageView object on a storyboard/xib file, then you could so something like the following...

class ViewController: UIViewController {
    var bgImage: UIImageView?

    override func viewDidLoad() {

        var image: UIImage = UIImage(named: "afternoon")!
        bgImage = UIImageView(image: image)
        bgImage!.frame = CGRectMake(0,0,100,200)

What does an exclamation mark before a cell reference mean?

When entered as the reference of a Named range, it refers to range on the sheet the named range is used on.

For example, create a named range MyName refering to =SUM(!B1:!K1)

Place a formula on Sheet1 =MyName. This will sum Sheet1!B1:K1

Now place the same formula (=MyName) on Sheet2. That formula will sum Sheet2!B1:K1

Note: (as pnuts commented) this and the regular SheetName!B1:K1 format are relative, so reference different cells as the =MyName formula is entered into different cells.

How to Select Top 100 rows in Oracle?

Assuming that create_time contains the time the order was created, and you want the 100 clients with the latest orders, you can:

  • add the create_time in your innermost query
  • order the results of your outer query by the create_time desc
  • add an outermost query that filters the first 100 rows using ROWNUM


     SELECT * FROM (
          ROW_NUMBER() OVER(PARTITION BY client_id ORDER BY create_time DESC) rn 
        FROM order
      WHERE rn=1
      ORDER BY create_time desc
  ) WHERE rownum <= 100

UPDATE for Oracle 12c

With release 12.1, Oracle introduced "real" Top-N queries. Using the new FETCH FIRST... syntax, you can also use:

      ROW_NUMBER() OVER(PARTITION BY client_id ORDER BY create_time DESC) rn 
    FROM order
  WHERE rn = 1
  ORDER BY create_time desc

How to overwrite the output directory in spark

UPDATE: Suggest using Dataframes, plus something like ... .write.mode(SaveMode.Overwrite) ....

Handy pimp:

implicit class PimpedStringRDD(rdd: RDD[String]) {
    def write(p: String)(implicit ss: SparkSession): Unit = {
      import ss.implicits._

For older versions try

yourSparkConf.set("spark.hadoop.validateOutputSpecs", "false")
val sc = SparkContext(yourSparkConf)

In 1.1.0 you can set conf settings using the spark-submit script with the --conf flag.

WARNING (older versions): According to @piggybox there is a bug in Spark where it will only overwrite files it needs to to write it's part- files, any other files will be left unremoved.

How do I properly set the Datetimeindex for a Pandas datetime object in a dataframe?

To simplify Kirubaharan's answer a bit:

df['Datetime'] = pd.to_datetime(df['date'] + ' ' + df['time'])
df = df.set_index('Datetime')

And to get rid of unwanted columns (as OP did but did not specify per se in the question):

df = df.drop(['date','time'], axis=1)

awk - concatenate two string variable and assign to a third

Concatenating strings in awk can be accomplished by the print command AWK manual page, and you can do complicated combination. Here I was trying to change the 16 char to A and used string concatenation:

echo    CTCTCTGAAATCACTGAGCAGGAGAAAGATT | awk -v w=15 -v BA=A '{OFS=""; print substr($0, 1, w), BA, substr($0,w+2)}'

I used the substr function to extract a portion of the input (STDIN). I passed some external parameters (here I am using hard-coded values) that are usually shell variable. In the context of shell programming, you can write -v w=$width -v BA=$my_charval. The key is the OFS which stands for Output Field Separate in awk. Print function take a list of values and write them to the STDOUT and glue them with the OFS. This is analogous to the perl join function.

It looks that in awk, string can be concatenated by printing variable next to each other:

echo xxx | awk -v a="aaa" -v b="bbb" '{ print a b $1 "string literal"}'
# will produce: aaabbbxxxstring literal