Tutorial by Examples: e

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...

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...

In Python 3 the cmp built-in function was removed, together with the __cmp__ special method. From the documentation: The cmp() function should be treated as gone, and the __cmp__() special method is no longer supported. Use __lt__() for sorting, __eq__() with __hash__(), and other rich compariso...

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 (jdoe@example.com) * @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...

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...

# load the library library(ggplot2) # create a blank canvas g <- ggplot(data = diamonds) g + geom_bar(aes(x = cut, fill = cut)) + scale_fill_discrete(guide = guide_legend(title = "CUT", keywidth = 2, ...

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 ...

Detailed instructions on getting android-activity set up or installed.

A reference is a scalar variable (one prefixed by $ ) which “refers to” some other data. my $value = "Hello"; my $reference = \$value; print $value; # => Hello print $reference; # => SCALAR(0x2683310) To get the referred-to data, you de-reference it. say ${$reference}...

Array References are scalars ($) which refer to Arrays. my @array = ("Hello"); # Creating array, assigning value from a list my $array_reference = \@array; These can be created more short-hand as follows: my $other_array_reference = ["Hello"]; Modifying / Using array ref...

Html5-Canvas ... Is an Html5 element. Is supported in most modern browsers (Internet Explorer 9+). Is a visible element that is transparent by default Has a default width of 300px and a default height of 150px. Requires JavaScript because all content must be programmatically added to the Canv...