If you want two or more arguments to be mutually exclusive. You can use the function argparse.ArgumentParser.add_mutually_exclusive_group(). In the example below, either foo or bar can exist but not both at the same time.
import argparse
parser = argparse.ArgumentParser()
group = parser.add_mut...
Create a DataFrame from multiple lists by passing a dict whose values lists. The keys of the dictionary are used as column labels. The lists can also be ndarrays. The lists/ndarrays must all be the same length.
import pandas as pd
# Create DF from dict of lists/ndarrays
df = pd.DataFrame({'...
Only when the foreach statement moves to the next item does the iterator block evaluate up to the next yield statement.
Consider the following example:
private IEnumerable<int> Integers()
{
var i = 0;
while(true)
{
Console.WriteLine("Inside iterator: " + i...
If an iterator method has a yield inside a try...finally, then the returned IEnumerator will execute the finally statement when Dispose is called on it, as long as the current point of evaluation is inside the try block.
Given the function:
private IEnumerable<int> Numbers()
{
yield re...
To modify an existing column in Rails with a migration, run the following command:
rails g migration change_column_in_table
This will create a new migration file in db/migration directory (if it doesn’t exist already), which will contain the file prefixed with timestamp and migration file name w...
Function level annotations help IDEs identify return values or potentially dangerous code
/**
* Adds two numbers together.
*
* @param Int $a First parameter to add
* @param Int $b Second parameter to add
* @return Int
*/
function sum($a, $b)
{
return (int) $a + $b;
}
/**
* ...
File level metadata applies to all the code within the file and should be placed at the top of the file:
<?php
/**
* @author John Doe ([email protected])
* @copyright MIT
*/
If a class extends another class and would use the same metadata, providing it @inheritDoc is a simple way for use the same documentation. If multiple classes inherit from a base, only the base would need to be changed for the children to be affected.
abstract class FooBase
{
/**
* @par...
Maybe is used to represent possibly empty values - similar to null in other languages. Usually it is used as the output type of functions that can fail in some way.
Consider the following function:
halve :: Int -> Maybe Int
halve x
| even x = Just (x `div` 2)
| odd x = Nothing
Think ...
Let's say you need to implement an automatic search box, but the search operation is somewhat costly, like sending a web request or hitting up a database. You may want to limit the amount of search being done.
For example, the user is typing "C# Reactive Extensions" in the search box :
I...
There are two operators for filtering duplicates:
emails.Distinct(); // Never see the same value twice
emails.DistinctUntilChanged(); // Never see the same value twice in a row
You can also pass in a predicate:
emails.DistinctUntilChanged(x => x.Length); // Never see the same length email t...
Let's use *norm as an example. From the documentation:
dnorm(x, mean = 0, sd = 1, log = FALSE)
pnorm(q, mean = 0, sd = 1, lower.tail = TRUE, log.p = FALSE)
qnorm(p, mean = 0, sd = 1, lower.tail = TRUE, log.p = FALSE)
rnorm(n, mean = 0, sd = 1)
So if I wanted to know the value of a standard no...
In order to define a variable inside a linq expression, you can use the let keyword. This is usually done in order to store the results of intermediate sub-queries, for example:
int[] numbers = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
var aboveAverages = from number in numbers
l...
The \b metacharacter
To make it easier to find whole words, we can use the metacharacter \b. It marks the beginning and the end of an alphanumeric sequence*. Also, since it only serves to mark this locations, it actually matches no character on its own.
*: It is common to call an alphanumeric sequ...
In order to enable a multidex configuration you need:
to change your Gradle build configuration
to use a MultiDexApplication or enable the MultiDex in your Application class
Gradle configuration
In app/build.gradle add these parts:
android {
compileSdkVersion 24
buildToolsVersion ...
The dexcount plugin counts methods and class resource count after a successful build.
Add the plugin in the app/build.gradle:
apply plugin: 'com.android.application'
buildscript {
repositories {
mavenCentral() // or jcenter()
}
dependencies {
classpath 'com.ge...
While in insert mode, press <C-o> to temporarily leave insert mode and execute a one-off normal command.
Example
<C-o>2w jumps to the second word to the left and returns to insert mode.
Note: Repeating with . will only repeat the actions from returning to insert mode
This allows for ...
C++11 introduced final specifier which forbids method overriding if appeared in method signature:
class Base {
public:
virtual void foo() {
std::cout << "Base::Foo\n";
}
};
class Derived1 : public Base {
public:
// Overriding Base::foo
void foo() f...
