Code Card - Quickly Search Common Code Snippets

Python For Loop

sequence = range(10)
for x in sequence:
    ...

Python has one of the simplest types of For Loops of any language. The 'in' operator can be used to easily iterate over any sequence type.

Java For Loop

for ( int x = 0; x < 10; x++ ) {
    ...
}

Java uses the traditional For Loop syntax which involves defining an iteration variable, looping condition, and increment.

Javascript For Loop

for ( var x = 0; x < 10; x++ ) {
    ...
}

Javascript uses the traditional For Loop syntax which involves defining an iteration variable, looping condition, and increment.

C For Loop

for ( int x = 0; x < 10; x++ ) {
    ...
}

C uses the traditional For Loop syntax which involves defining an iteration variable, looping condition, and increment.

PHP For Loop

for ( $x = 0; $x < 10; $x++ ) {
    ...
}

PHP uses the traditional For Loop syntax which involves defining an iteration variable, looping condition, and increment.

Python While Loop

x = 0
while (x < 10):
    ...
    x += 1

Python uses a very clean While Loop syntax. The loop continues running as long as the looping condition remains true. The looping variable can be updated in the loop.

Java While Loop

int x = 0;
while (x < 10) {
    ...
    x++;
}

Java uses the traditional While Loop syntax. The loop continues running as long as the looping condition remains true. The looping variable can be updated in the loop.

Javascript While Loop

var x = 0;
while (x < 10) {
    ...
    x++;
}

Javascript uses the traditional While Loop syntax. The loop continues running as long as the looping condition remains true. The looping variable can be updated in the loop.

C While Loop

int x = 0;
while (x < 10) {
    ...
    x++;
}

C uses the traditional While Loop syntax. The loop continues running as long as the looping condition remains true. The looping variable can be updated in the loop.

PHP While Loop

$x = 0;
while ($x < 10) {
    ...
    $x++;
}

PHP uses the traditional While Loop syntax. The loop continues running as long as the looping condition remains true. The looping variable can be updated in the loop.

Python Variable Assignment

a = 0
b = "Hello"
c = ["C", "h", "e", "e", "s", "e"]
d = { 1: "x", 2: "y", 3: "z" }
e = True

Python variables can be assigned on the fly without declaring their types first. Integers, strings, lists, dictionaries, and booleans can all be defined using a single equals sign.

Java Variable Assignment

int a = 0;
char b = 'b';
String c = "Hello";
String[] d = {"C", "h", "e", "e", "s", "e"};
boolean e = true;

Java variables must have their types declared before assignment. Integers, characters, strings, arrays, and booleans are shown here.

Javascript Variable Assignment

var a = 0;
var b = "Hello";
var c = ["C", "h", "e", "e", "s", "e"];
var d = { 1: "x", 2: "y", 3: "z" };
var e = true;

Javascript variables can be assigned on the fly without declaring their types first. Integers, strings, lists, objects, and booleans can all be defined using the `var` keyword and an equals sign.

C Variable Assignment

int a = 0;
char b = 'b';
String c = "Hello";
String[] d = {"C", "h", "e", "e", "s", "e"};
boolean e = true;

C variables must have their types declared before assignment. Integers, characters, strings, arrays, and booleans are shown here.

PHP Variable Assignment

$a = 0;
$b = "Hello";
$c = ["C", "h", "e", "e", "s", "e"];
$d["1"] = "x"; $d["2"] = "y"; $d["3"] = "z";
$e = true;

PHP variables can be assigned on the fly without declaring their types first. Integers, strings, arrays, and booleans can all be defined using the `$` symbol and an equals sign.

Python If ... Else

if ( x == 1 ):
    ...
elif ( x == 2 ):
    ...
else:
    ...

Python conditional statements are very simple indeed.

Java If ... Else

if ( x == 1 ) {
    ...
} else if ( x == 2 ) {
    ...
} else {
    ...
}

Java uses the traditional syntax for conditional statements.

Javascript If ... Else

if ( x == 1 ) {
    ...
} else if ( x == 2 ) {
    ...
} else {
    ...
}

Javascript uses the traditional syntax for conditional statements.

C If ... Else

if ( x == 1 ) {
    ...
} else if ( x == 2 ) {
    ...
} else {
    ...
}

C uses the traditional syntax for conditional statements.

PHP If ... Else

if ( x == 1 ) {
    ...
} elseif ( x == 2 ) {
    ...
} else {
    ...
}

PHP almost uses the traditional syntax for conditional statements, but note that the `elseif` is a single word.

Python Function

def sum(i, j):
    return i + j

Python functions are created using the `def` statement. The return type and parameter types do not need to be specified. All indented lines under the `def` statement make up the function's scope.

Java Function

int sum(int i, int j) {
    return i + j;
}

Java functions must declare the return type before the function name, as well as the parameter types. The function's scope is delineated by curly braces.

Javascript Function

function sum(i, j) {
    return i + j;
}

Javascript functions are defined using the `function` statement. The return type and parameter types do not need to be specified. The function's scope is delineated by curly braces.

C Function

int sum(int i, int j) {
    return i + j;
}

C functions must declare the return type before the function name, as well as the parameter types. The function's scope is delineated by curly braces.

PHP Function

function sum($i, $j) {
    return $i + $j;
}

PHP functions are defined using the `function` statement. The return type and parameter types do not need to be specified. The function's scope is delineated by curly braces.

Python Class

class Person:
    def __init__(self, name):
        self.name = name
    def greet(self):
        return "I am " + self.name

Python classes contain member attributes and methods. The `__init__` method defines the constructor. By convention, `self` is the first parameter in each method and represents the instance of the class. Getter and setter methods are not needed since attributes are not private.

Java Class

public class Person {
    private String name;
    public Person(String name) {
        this.name = name;
    }
    public String getName() {
        return name;
    }
}

Java classes contain member attributes and methods. Constructors are methods created with the same name as the class itself. Members are private by default, so public getters and setters must be defined for attribute access.

Javascript Class

class Person {
    constructor(name) {
        this.name = name;
    }
    greet() {
        return "I am " + this.name;
    }
}

Javascript classes are relatively new additions to the language. The `constructor` keyword defines the constructor. Getter and setter methods are not needed since attributes are not private.

C Class

Gone fishin!

C does not have classes. That's why C++ was created. The closest thing in C is the `struct`, which has it's own card.

PHP Class

class Person {
    public function __construct($name) {
        $this->name = $name;
    }
    public function greet() {
        return $this->name;
    }
}

PHP classes contain member attributes and methods. The `__construct` method defines the constructor. Getter and setter methods are not needed since attributes are not private.

Python Try ... Catch / Except

try:
    ...
except:
    ...
finally:
    ...

Python will try to run the code in the `try` block. If an exception occurs the code in the `except` block will run. Specific exceptions can be caught using the `except(Exception1, Exception2, ...)` syntax. The code in the `finally` block will always execute.

Java Try ... Catch / Except

try {
    ...
} catch ( Exception e ) {
    ...
} finally {
    ...
}

Java will try to run the code in the `try` block. If a matched exception occurs the code in the `catch` block will run. The code in the `finally` block will always execute.

Javascript Try ... Catch / Except

try {
    ...
} catch ( e ) {
    ...
} finally {
    ...
}

Javascript will try to run the code in the `try` block. If an exception occurs the code in the `catch` block will run. Exception matching must be performed in the `catch` block. The code in the `finally` block will always execute.

C Try ... Catch / Except

Gone fishin!

C does not directly support exceptions.

PHP Try ... Catch / Except

try {
    ...
} catch ( Exception $e ) {
    ...
} finally {
    ...
}

PHP will try to run the code in the `try` block. If an exception occurs the code in the `catch` block will run. Specific exceptions can be caught using the `catch(Exception1 | Exception2 $e)` syntax. The code in the `finally` block will always execute.

Python Switch

Gone fishin!

Python does not have a built-in Switch statement.

Java Switch

switch( expression ) {
    case value1:
        ...;
        break;
    case value2:
        ...;
        break;
    default:
        ...;
        break;
}

The Java Switch statement accepts any expression or variable that can assume multiple values. Depending on the values, different code can be executed corresponding to each `case` statement. The `default` case is a catchall in the event that none of the explicit cases occur.

Javascript Switch

switch( expression ) {
    case value1:
        ...;
        break;
    case value2:
        ...;
        break;
    default:
        ...;
}

The Javascript Switch statement accepts any expression or variable that can assume multiple values. Depending on the values, different code can be executed corresponding to each `case` statement. The `default` case is a catchall in the event that none of the explicit cases occur.

C Switch

switch( expression ) {
    case value1:
        ...;
        break;
    case value2:
        ...;
        break;
    default:
        ...;
}

The C Switch statement accepts any expression or variable that can assume multiple values. Depending on the values, different code can be executed corresponding to each `case` statement. The `default` case is a catchall in the event that none of the explicit cases occur.

PHP Switch

switch( expression ) {
    case value1:
        ...;
        break;
    case value2:
        ...;
        break;
    default:
        ...;
}

The PHP Switch statement accepts any expression or variable that can assume multiple values. Depending on the values, different code can be executed corresponding to each `case` statement. The `default` case is a catchall in the event that none of the explicit cases occur.

Python Import / Include

import module1
import module1 as m1
from module1 import object1
from module1 import object1 as o1
from module1 import *

Python imports are used to access external code within modules. The `from` keyword can be used to import a specific object or function from a module. The `as` keyword can be used to rename the imported module or object. An asterisk can be used to import all toplevel objects from a module.

Java Import / Include

import library.packagename.classname;
import library.packagename.*;

Java imports are used to conveniently reference code from other packages on the classpath. Classes can be imported individually or all classes can be imported from a package using the asterisk.

Javascript Import / Include

import {obj1, obj2} from './mod.js';
import {obj1 as o1} from './mod.js';
import * as obj from './mod.js';

Javascript imports are used to access objects exported from other modules. Objects can be renamed with the `as` keyword. All objects exported from a module can be imported using an asterisk.

C Import / Include

#include <header.h>

The #include preprocessing directive is used in C programs to access functions or objects that live in header and user files.

PHP Import / Include

use \library\package\module;

PHP modules can be imported and accessed with the `use` statement.

Python Print

print('Hi')

The Python Print function prints a string to the standard output.

Java Print

System.out.println("Hi");

The `println` function from the `System.out` library is used to print strings to standard output in Java, with a newline added to the end.

Javascript Print

console.log('Hi');

In Javascript, the `console.log` function is used to print text to the console.

C Print

printf("%s", "Hi");

In C, the `printf` function is used to print a formatted string to the standard output.

PHP Print

print "Hi";
echo "Hi";

In PHP, the `print` or `echo` functions can be used to output text.

Python Arithmetic Operators

a = 8 + 4
b = a - 7
c = a * 8
d = b / a
e = b ** a
r = e % 2

Python uses the familiar set of arithmetic operators to add, subtract, multiply, divide, exponentiate, and modulo.

Java Arithmetic Operators

int a = 8 + 4;
int b = a - 7;
int c = b * 8;
int d = b / a;
int e = 2 ** 4;
int r = 10 % 3;

Java uses the familiar set of arithmetic operators to add, subtract, multiply, divide, exponentiate, and modulo.

Javascript Arithmetic Operators

var a = 8 + 4;
var b = a - 7;
var c = a * 8;
var d = b / a;
var e = b ** a;
var r = e % 2;

Javascript uses the familiar set of arithmetic operators to add, subtract, multiply, divide, exponentiate, and modulo.

C Arithmetic Operators

int a = 8 + 4;
int b = a - 7;
int c = b * 8;
int d = b / a;
int e = 2 ** 4;
int r = 10 % 3;

C uses the familiar set of arithmetic operators to add, subtract, multiply, divide, exponentiate, and modulo.

PHP Arithmetic Operators

$a = 8 + 4;
$b = $a - 7;
$c = $b * 8;
$d = $b / $a;
$e = 2 ** 4;
$r = $e % 2;

PHP uses the familiar set of arithmetic operators to add, subtract, multiply, divide, exponentiate, and modulo.

Python Comparison Operators

a == b
b > a
b < a
b <= a
b >= a
b <> a

Python uses the standard set of operators to test equality, greater than, less than, etc. Equality uses two equals signs `==` to distinguish it from the assignment operator `=`. To test inequality, Python uses the `<>` operator. Each conditional expression returns a boolean value, either True or False.

Java Comparison Operators

a == b
a < b
a > b
a >= b
a <= b
a != b

Java uses the standard set of operators to test equality, greater than, less than, etc. Equality uses two equals signs `==` to distinguish it from the assignment operator `=`. To test inequality, Java uses the '!=' operator. Each conditional expression returns a boolean value.

Javascript Comparison Operators

a == b
a === b
a < b
a > b
a >= b
a <= b
a != b
a !== b

Javascript uses the standard set of operators to test equality, greater than, less than, etc. Equality uses two equals signs `==` to distinguish it from the assignment operator `=`. To test inequality, Javascript uses the `!=` operator. Notice the `===` and `!==` operators compare value AND type.

C Comparison Operators

a == b
a < b
a > b
a >= b
a <= b
a != b

C uses the standard set of operators to test equality, greater than, less than, etc. Equality uses two equals signs `==` to distinguish it from the assignment operator '='. To test inequality, C uses the `!=` operator. Each conditional expression returns a boolean value.

PHP Comparison Operators

$a == $b
$a === $b
$a < $b
$a > $b
$a >= $b
$a <= $b
$a != $b
$a <> $b
$a !== $b

PHP uses the standard set of operators to test equality, greater than, less than, etc. Equality uses two equals signs `==` to distinguish it from the assignment operator `=`. To test inequality, PHP uses `!=` or `<>`. Notice the `===` and `!==` operators compare value AND type.

Python Logical Operators

a and b
a or b
not a

Python uses english words to represent the logical operators: and, or, not.

Java Logical Operators

a && b
a || b
!a

Java uses the respective symbols to represent the logical operators: and, or, not.

Javascript Logical Operators

a && b
a || b
!a

Javascript uses the respective symbols to represent the logical operators: and, or, not.

C Logical Operators

a && b
a || b
!a

C uses the respective symbols to represent the logical operators: and, or, not.

PHP Logical Operators

a && b
a and b
a || b
a or b
!a

PHP uses the respective symbols to represent the logical operators: and, or, not.

Python Break

while a > b:
    ...
    break

Python uses the break statement to break out of the enclosing loop.

Java Break

for ( int x : numbers ) {
     ...
     break;
}

Java uses the break statement to break out of the enclosing loop.

Javascript Break

for ( i = 0; i < 5; i++ ) {
    ...
    break;
}

Javascript uses the break statement to break out of the enclosing loop.

C Break

for ( int i = 0; i < 5; i++ ) {
    ...
    break;
}

C uses the break statement to break out of the enclosing loop.

PHP Break

for ( $i = 0; $i < 5; $i++ ) {
    ...
    break;
}

PHP uses the break statement to break out of the enclosing loop.

Python Continue

while a > b:
    ...
    continue

Python uses the continue statement to start the next instruction at the beginning of the enclosing loop.

Java Continue

for ( int x : numbers ) {
     ...
     continue;
}

Java uses the continue statement to start the next instruction at the beginning of the enclosing loop.

Javascript Continue

for ( i = 0; i < 5; i++ ) {
    ...
    continue;
}

Javascript uses the continue statement to start the next instruction at the beginning of the enclosing loop.

C Continue

for ( int i = 0; i < 5; i++ ) {
    ...
    continue;
}

C uses the continue statement to start the next instruction at the beginning of the enclosing loop.

PHP Continue

for ( $i = 0; $i < 5; $i++ ) {
    ...
    continue;
}

PHP uses the continue statement to start the next instruction at the beginning of the enclosing loop.

Python Comments

# This is a simple single line comment
"""The triple quote
comment can span many lines"""

Python uses two formats for comments, depending on whether they are single-line or multi-line comments.

Java Comments

// This is a single line comment
/* This comment can span many lines */

Java uses two formats for comments, depending on whether they are single-line or multi-line comments.

Javascript Comments

// This is a single line comment
/* This comment can span many lines */

Javascript uses two formats for comments, depending on whether they are single-line or multi-line comments.

C Comments

/* This comment can span many lines */
// This was not originally supported by C

C was the original language to introduce this multi-line style for comments. However later versions of C started supporting the C++ style single-line comments.

PHP Comments

# This is a single line comment
// This is also a single line comment
/* This comment can span many lines */

PHP supports shell style comments and both single and multi-line C style comments.

Python Return

def func( ):
    ...
    return a, b

Python uses the return statement to exit from a function, optionally returning zero, one, more values.

Java Return

class A {
    int fun( ) {
        ...
        return x;
    }
}

Java uses the return statement to exit from a function, optionally returning a value.

Javascript Return

function fun( ) {
    ...
    return x;
}

Javascript uses the return statement to exit from a function, optionally returning a value.

C Return

int fun( ) {
    ...
    return x;
}

C uses the return statement to exit from a function, optionally returning a value.

PHP Return

function fun( ) {
    ...
    return $x;
}

PHP uses the return statement to exit from a function, optionally returning a value.

Python Ternary Operator

x if ( x > 0 ) else y

Python uses a unique syntax for the ternary operator to shorten the traditional if-else clause.

Java Ternary Operator

( x > 0 ) ? x : y;

Java uses the ternary operator as short hand for the if-else clause. If the condition evaluates to true, the value after the question mark is returned. Otherwise, the value after the colon is returned.

Javascript Ternary Operator

( x > 0 ) ? x : y;

Javascript uses the ternary operator as short hand for the if-else clause. If the condition evaluates to true, the value after the question mark is returned. Otherwise, the value after the colon is returned.

C Ternary Operator

( x > 0 ) ? x : y;

C uses the ternary operator as short hand for the if-else clause. If the condition evaluates to true, the value after the question mark is returned. Otherwise, the value after the colon is returned.

PHP Ternary Operator

( $x > 0 ) ? $x : $y

PHP uses the ternary operator as short hand for the if-else clause. If the condition evaluates to true, the value after the question mark is returned. Otherwise, the value after the colon is returned.

Python Raise / Throw

if x > 20:
    raise Exception("x must be less than 20")

Python uses the raise statement to generate an exception under user-defined conditions.

Java Raise / Throw

if ( x > 20 ) {
    throw new Exception("x must be < 20");
}

Java uses the throw statement to generate an exception under user-defined conditions.

Javascript Raise / Throw

if ( x > 20 ) {
    throw "x must be < 20";    
}

Javascript uses the throw statement to generate an exception under user-defined conditions.

C Raise / Throw

Gone fishin!

C does not support exceptions, one must rely on return values or asserts to handle exceptional conditions.

PHP Raise / Throw

if ( $x > 20 ) {
    throw new Exception("x must be > 20");
}

PHP uses the throw statement to generate an exception under user-defined conditions.

Python Assert

assert x > b

Python uses the assert statement to terminate a program when an expression is false.

Java Assert

assert x > 20: "x must be > 20;

Java uses the assert statement to terminate a program when an expression is false.

Javascript Assert

assert( x > 20 );

Javascript uses the assert statement to terminate a program when an expression is false.

C Assert

#include <assert.h>
...
void fun() {
    ...
    assert( x > 20 );
}

C uses the assert statement to terminate a program when an expression is false.

PHP Assert

result = assert( $x > 20, "x must be > 20" );

PHP uses the assert statement to terminate a program when an expression is false. The behavior of assert is controlled by assert_options().

Python Dates

import datetime
n = datetime.datetime.now()

Python uses the datetime module to get the current time.

Java Dates

Date now = new Date();

Java uses the Date() class to get the current time.

Javascript Dates

var now = Date.now();

Javascript the Date() class can be used to get the current time.

C Dates

#include <time.h>
...
time_t now = time(NULL);

C uses the time library to get the current date and time.

PHP Dates

$now = date("Y/m/d");

PHP uses the date function with a format string to get the current date and time.

Python Open File

f1 = open( "f.txt", "r" )
f2 = open( "f.txt", "w" )
f3 = open( "f.txt", "a" )

Python can open a file for reading, writing, or appending, using the respective file mode as the second argument to the `open` function.

Java Open File

import java.io.File;
...
File file = new File( "f.txt" );

Java can open a file for reading or writing.

Javascript Open File

var f1 = fopen( "f.txt", 0 );
var f2 = fopen( "f.txt", 3 );

Javascript can open a file for reading or writing, depending on the value of the second argument to the `fopen` function. 0 is for reading, 3 is for writing.

C Open File

#include <stdio.h>
...
FILE *f1 = fopen( "f.txt", "r" );
FILE *f2 = fopen( "f.txt", "w" );
FILE *f3 = fopen( "f.txt", "a" );

C can open a file for reading, writing, or appending, using the respective file mode as the second argument to the `open` function.

PHP Open File

$f1 = fopen( "f.txt", "r" );
$f2 = fopen( "f.txt", "w" );

PHP can open a file for reading or writing using the respective file mode as the second argument to the `fopen` function.

Python Read from File

f = open( "f.txt", "r" )
content = f.read()

Python can read all data from a file object that was opened in read mode using the `read()` method.

Java Read from File

import java.io.File;
import java.util.Scanner;
...
File f = new File( "f.txt" );
Scanner s = new Scanner(f);
while ( s.hasNextLine() ) {
    String l = s.nextLine();
    System.out.println(l);
}

Java can use the scanner class to read from a file, line by line.

Javascript Read from File

var f = fopen( "f.txt", 0 );
var content = fread( f, len );

Javascript can read the content of an open file using the `fread()` function. The second argument to `fread()` specifies the length of content to read.

C Read from File

FILE *f = fopen( "f.txt", "r" );
char c = fgetc(f);
while ( c != EOF ) {
    printf("%c", c);
    c = fgets(f);
}

C can use the `fgetc()` function to read characters from a file one by one.

PHP Read from File

$f = fopen( "f.txt", "r" );
$s = filesize("f.txt");
$c = fread( $f, $s );

PHP can read a file with the `fread()` function. The second argument is the filesize. The `filesize()` function can be used to get the size of the entire file.

Python Write to File

f = open( "f.txt", "w" )
f.write( "text" )

Python can write to an open file object using the `write` method.

Java Write to File

import java.io.FileWriter;
...
FileWriter fw = new FileWriter( "f.txt" );
fw.write( "text" );

Java can write to a file using the FileWriter object and its `write` method.

Javascript Write to File

var f = fopen( "f.txt", 3 );
fwrite( f, "text" );

Javascript can write to an open file using the `fwrite` function.

C Write to File

FILE *f = fopen( "f.txt", "w" );
fprintf(f, "%s", "text");

C can write to an open file using the `fprintf()` function.

PHP Write to File

$f = fopen( "f.txt", "w" );
fwrite( $f, "text" );

PHP can write to an open file using the `fwrite()` function.

Python Close File

f.close()

Python uses the `close()` method to close files.

Java Close File

Gone fishin!

Java doesn't have a close function since a file opened with `new File('f.txt')` represents a path and not the file itself. Java utilities to read and write from files handle the closing process.

Javascript Close File

fclose(f);

Javascript uses the `fclose()` function to close files.

C Close File

fclose(f);

C uses the `fclose()` function to close files.

PHP Close File

fclose($f);

PHP uses the `fclose()` function to close files.

Python User Input

x = input("Type input: ")

Python uses the `input()` function prompt the user for input.

Java User Input

import java.util.Scanner;
Scanner s = new Scanner(System.in);
System.out.println("Type input: ");
String i = s.nextLine();

Java uses a Scanner object combined with the standard input to read values from the user.

Javascript User Input

var i = prompt("Type input: ");

Javascript uses the `prompt()` function to display a prompt dialog to the user.

C User Input

#include <stdio.h>
...
char s[10];
printf("Type input: ");
fgets(s, 10, stdin);

C uses the `fgets()` function to accept input from an input stream. In this case we specify that `fgets` accepts 10 characters of input from the standard input.

PHP User Input

echo "Type input: ";
$f = fopen( "php://stdin", "r" );
$line = fgets($f);

PHP uses the `fopen()` with the standard input stdin and `fgets()` to read input from a user.

Python Anonymous / Lambda Function

lambda x : 2 * x

Python uses the lambda keyword to create anonymous functions.

Java Anonymous / Lambda Function

(int x) -> 2 * x;

Java uses the arrow operator to map a function expression to a return value and create an anonymous function.

Javascript Anonymous / Lambda Function

function() {
    alert("Hi");
}

Javascript creates an anonymous function any time the `function` statement is used without specifying a function name.

C Anonymous / Lambda Function

Gone fishin!

C does not support anonymous functions.

PHP Anonymous / Lambda Function

function() {
    echo "Hi.";
}

PHP creates an anonymous function any time the `function` statement is used without specifying a function name.

Python Inheritance

class ChildClass( ParentClass ):
    pass

Python implements inheritance by allowing the user to specify a superclass as an argument in the subclass definition.

Java Inheritance

class ChildClass extends ParentClass {
    ...
}

Java implements inheritance via the `extends` keyword.

Javascript Inheritance

function ChildClass( x, y ) {
    ParentClass.call( this, x );
    this.y = y;
}
ChildClass.prototype = new ParentClass();

Javascript allows creating an inheritance model by calling the constructor of the superclass and passing any required parameters. Note the last line where we set the prototype of the subclass to a new empty instance of the superclass.

C Inheritance

Gone fishin!

C does not support inheritance.

PHP Inheritance

class ChildClass extends ParentClass {
    ...
}

PHP implements inheritance via the `extends` keyword.

Python Null / None / Undefined

x = None

Python uses the `None` keyword to represent null values.

Java Null / None / Undefined

String x = null;

Java uses the `null` keyword to represent null values.

Javascript Null / None / Undefined

var x = null;
var y = undefined;

Javascript uses the `null` or `undefined` keyword to represent null values.

C Null / None / Undefined

char *x = NULL;

C uses a macro to define NULL as the actual null value '\0', or the NULL byte.

PHP Null / None / Undefined

$val = NULL;

PHP uses the `NULL` keyword to represent null values.

Python Pass

if True:
    pass

Python uses pass to represent a placeholder statement that does nothing. The reason Python needs this statement is that brackets aren't used to identify the end of an empty scoped block.

Java Pass

if ( true ) { }

Java uses empty brackets to represent a placeholder statement that does nothing.

Javascript Pass

if ( true ) { }

Javascript uses empty brackets to represent a placeholder statement that does nothing.

C Pass

if ( 1 ) { }

C uses empty brackets to represent a placeholder statement that does nothing.

PHP Pass

if ( true ) { }

PHP uses empty brackets to represent a placeholder statement that does nothing.

Python Advanced Assignment

a += 5
a -= 5
a *= 5
a /= 5
a %= 5

Python combines a logical operation (add, subtract, multiply, divide and modulo) with an equals sign, subsequently assigning the result of the operation to the left operand.

Java Advanced Assignment

int a += 5;
int a -= 5;
int a *= 5;
int a /= 5;
int a %= 5;

Java combines a logical operation (add, subtract, multiply, divide and modulo) with an equals sign, subsequently assigning the result of the operation to the left operand.

Javascript Advanced Assignment

var a += 5;
var a -= 5;
var a *= 5;
var a /= 5;
var a %= 5;

Javascript combines a logical operation (add, subtract, multiply, divide and modulo) with an equals sign, subsequently assigning the result of the operation to the left operand.

C Advanced Assignment

int a += 5;
int a -= 5;
int a *= 5;
int a /= 5;
int a %= 5;

C combines a logical operation (add, subtract, multiply, divide and modulo) with an equals sign, subsequently assigning the result of the operation to the left operand.

PHP Advanced Assignment

$a += 5;
$a -= 5;
$a *= 5;
$a /= 5;
$a %= 5;

PHP combines a logical operation (add, subtract, multiply, divide and modulo) with an equals sign, subsequently assigning the result of the operation to the left operand.

Python Casting

w = 1;
x = str(w)
y = int(x)
z = float(y)

Python uses a set of type functions for casting.

Java Casting

int w = 1;
String x = (String) w;
int y = (int) x;
float z = (float) y;

Java uses the type wrapped in parenthesis before the variable for casting.

Javascript Casting

var w = 1;
var x = String(w);
var y = Number(x);

Javascript uses a set of type functions and built-in object methods for casting.

C Casting

int w = 1;
long x = (long) w;
float y = (float) x;
double z = (double) y;

C uses the type wrapped in parenthesis before the variable for casting.

PHP Casting

$w = 1;
$x = (string) w;
$y = (int) x;
$z = (float) y;

PHP uses the type wrapped in parenthesis before the variable for casting.

Python Bitwise Operators

b = a & 0x1001
b = a | 0x1001
b = ~a
b = a ^ 0x4
b = a << 2
b = a >> 2

Python supports the respective bitwise operations: and, or, not, xor, shift right and shift left.

Java Bitwise Operators

int b = a & 0x1001;
int b = a | 0x1001;
int b = ~a;
int b = a ^ 0x4;
int b = a << 2;
int b = a >> 2;

Java supports the respective bitwise operations: and, or, not, xor, shift right and shift left.

Javascript Bitwise Operators

var b = a & 0x1001;
var b = a | 0x1001;
var b = ~a;
var b = a ^ 0x4;
var b = a << 2;
var b = a >> 2;

Javascript supports the respective bitwise operations: and, or, not, xor, shift right and shift left.

C Bitwise Operators

int b = a & 0x1001;
int b = a | 0x1001;
int b = ~a;
int b = a ^ 0x4;
int b = a << 2;
int b = a >> 2;

C supports the respective bitwise operations: and, or, not, xor, shift right and shift left.

PHP Bitwise Operators

$b = $a & 0x1001;
$b = $a | 0x1001;
$b = ~$a;
$b = $a ^ 0x4;
$b = $a << 2;
$b = $a >> 2;

PHP supports the respective bitwise operations: and, or, not, xor, shift right and shift left.

Python Constructor

class Fake():
    def __init__(self, x):
        this.x = x

Python uses the special `__init__()` method with the conventional `self` argument to define the class constructor. `self` represents the instance of the class being referenced.

Java Constructor

class Fake {
    public Fake(String x) {
        this.x = x;
    }
}

Java implements constructors by recognizing methods that have the same name as the class. `this` represents the instance of the class being referenced.

Javascript Constructor

class Fake {
    constructor(x) {
       this.x = x;
    }
}

Javascript defines constructors using the `constructor()` method. `this` represents the instance of the class being referenced.

C Constructor

Gone fishin!

C does not supports classes and therefore does not support constructors.

PHP Constructor

class Fake {
    function __construct($x) {
       $this->x = $x;
    }
}

PHP defines constructors using the `__construct()` method. `$this` represents the instance of the class being referenced.

Python Create Instance

f = Fake("Hi")

Python will instantiate an object from a class definition by calling it with parenthesis and the respective arguments. Arguments will be passed to the class constructor.

Java Create Instance

Fake f = new Fake("Hi");

Java will instantiate an object from a class definition using the `new` keyword. Arguments will be passed to the class constructor.

Javascript Create Instance

var f = new Fake("Hi");

Javascript will instantiate an object from a class definition using the `new` keyword. Arguments will be passed to the class constructor.

C Create Instance

Gone fishin!

C does not support classes and therefore does not support instance creation.

PHP Create Instance

$f = new Fake("Hi");

PHP will instantiate an object from a class definition using the `new` keyword. Arguments will be passed to the class constructor.

Python List / Array Length

len(list)

The Python `len()` function returns the length of a list.

Java List / Array Length

arr.length;

Java arrays have the `length` property which can be used to return their length.

Javascript List / Array Length

arr.length;

Javascript arrays have the `length` property which can be used to return their length.

C List / Array Length

sizeof(arr) / sizeof(arr[0]);

C uses the `sizeof()` function to get the size of data types including arrays. Since size returns the total size or the array, we divide it by the size of an array item to get the the length.

PHP List / Array Length

count($array);

PHP uses the `count()` function to get the length of an array.

Python String Length

len("string")

The Python `len()` function returns the length of a string.

Java String Length

str.length();

The Java String class provides the `length()` method.

Javascript String Length

str.length;

Javascript strings have the length property.

C String Length

#include<string.h>
strlen("string");

C uses the `strlen()` function to get the length of strings.

PHP String Length

strlen("string");

PHP uses the `strlen()` function to get the length of strings.

Python Index List / Array

list[0]

Python uses square brackets to get a list index.

Java Index List / Array

arr[0];

Java uses square brackets to get an array index.

Javascript Index List / Array

arr[0];

Javascript uses square brackets to get an array index.

C Index List / Array

arr[0];

C uses square brackets to get an array index.

PHP Index List / Array

arr[0];

PHP uses square brackets to to get an array index.

Python Add to List / Array

list.append(x)

Python uses the `append()` method to add elements to a list.

Java Add to List / Array

ArrayList<String> arr = new ArrayList<String>();
arr.add(x);

The Java `ArrayList` class provides the `add()` method to append an element to an array.

Javascript Add to List / Array

arr.push(x);

Javascript uses the `push()` method to add elements to an array.

C Add to List / Array

arr[i] = element;

C uses direct index assignment to modify values in an array.

PHP Add to List / Array

array_push( $arr, $newItem );
$arr[] = $newItem;

PHP provides the `array_push()` function or direct item assignment to an empty index to add elements to an array.

Python Remove from List / Array

list.pop()

Python uses the `pop()` method to remove (and return) the last element from a list.

Java Remove from List / Array

ArrayList<String> arr = new ArrayList<String>();
arr.remove(i);

The Java ArrayList class provides the `remove()` method to remove an array element at the specified index.

Javascript Remove from List / Array

arr.pop();

Javascript uses the `pop()` method to remove (and return) the last element from an array.

C Remove from List / Array

arr[i] = NULL;

C uses direct item assignment to nullify an array element.

PHP Remove from List / Array

array_pop($arr);

PHP uses the `array_pop()` function to remove (and return) the last element from an array.

Python Sort List / Array

l = [2, 3, 1]
l.sort()
nl = sorted(l)

Python lists are sorted in-place with the `.sort()` method. To return a new sorted list instead of sorting in-place, use the built-in `sorted()` function instead.

Java Sort List / Array

import java.util.ArrayList;
import java.util.Collections; 
...
ArrayList<Integer> a = new ArrayList<Integer>();
a.add(2);
a.add(3);
a.add(1);
Collections.sort(a);

Java ArrayLists can be sorted in-place using the the `Collections.sort()` method.

Javascript Sort List / Array

var a = [2, 3, 1];
a.sort();

Javascript arrays are sorted in-place with the `.sort()` method.

C Sort List / Array

#include <stdio.h>
#include <stdlib.h>
...
int compare( const void* x, const void* y) {
    int int_x = *((int*)x);
    int int_y = *((int*)y);

    if (int_x == int_y) return 0;
    else if (int_x < int_y) return -1;
    else return 1;
}
int a[] = {2, 3, 1};
qsort( a, 3, sizeof(int), compare );

C arrays can be sorted using the `qsort()` function along with a custom defined comparison function.

PHP Sort List / Array

$a = [2, 3, 1]; 
sort($a);

PHP arrays can be sorted in-place using the `sort()` function.

Python Replace List / Array Item

l = [ "a", "b", "z" ]
l[2] = "c"

Python uses index assignment to replace existing list items.

Java Replace List / Array Item

import java.util.ArrayList;
...
ArrayList<String> a = new ArrayList<String>();
a.add("a");
a.add("b");
a.add("z");
a.set(2, "c");

Java uses the `.set()` method to replace an item in an ArrayList.

Javascript Replace List / Array Item

a = [ "a", "b", "z" ];
a[2] = "c";

Javascript uses index assignment to replace existing list items.

C Replace List / Array Item

char a[] = {'a', 'b', 'z'};
a[2] = 'c';

C uses index assignment to replace existing list items.

PHP Replace List / Array Item

$a = [ "a", "b", "z" ]; 
$a[2] = "c";

PHP uses index assignment to replace existing list items.

Python Slice List / Array

l = ["a", "b", "c", "d", "e"]
b = l[0:3]

Python uses the `:` operator to get a slice of a list. The number before the colon is the index of the first element of the slice, inclusive. The number after the colon is the index of the the last item of the slice, exclusive. This example slice will return ['a', 'b', 'c'].

Java Slice List / Array

import java.util.List;
import java.util.ArrayList;
...
List<String> a = new ArrayList<String>();
a.add("a");
a.add("b");
a.add("c");
a.add("d");
a.add("e");
List<String> b = a.subList(0, 3);

Java uses `.subList()` method to get an array slice. The first argument is the index of the first element of the slice, inclusive. The second argument is the index of the the last item of the slice, exclusive. This example slice will return ['a', 'b', 'c'].

Javascript Slice List / Array

var a = ["a", "b", "c", "d", "e"];
b = a.slice(0, 3);

Javascript uses `.slice()` method to get an array slice. The first argument is the index of the first element of the slice, inclusive. The second argument is the index of the the last item of the slice, exclusive. This example slice will return ['a', 'b', 'c'].

C Slice List / Array

char a[5] = {'a', 'b', 'c', 'd', 'e'};
char b[2];
memcpy(b, a, 3 * sizeof(*x));

C can effectively slice an array using the `memcpy()` function. The first argument is the array to copy the slice to. The second argument is the array to copy the slice from. The third argument is the size of the desired number of elements to slice. This example slice will return ['a', 'b', 'c'].

PHP Slice List / Array

$a = ["a", "b", "c", "d", "e"];
$b = array_slice($a, 0, 3);

PHP uses uses `array_slice()` function to get an array slice. The first argument is the index of the first element of the slice, inclusive. The second argument is the index of the the last item of the slice, exclusive. This example slice will return ['a', 'b', 'c'].

Python Replace Array Slice

l = ["a", "b", "c", "d", "e"]
l[0:3] = "x"

Python allows assignments to slices which will have the effect of replacing the slice. In this example the final list will be ['x', 'd', 'e']

Java Replace Array Slice

List<String> a = new ArrayList<String>();
a.add("a");
a.add("b");
a.add("c");
a.add("d");
a.add("e");
a = a.subList(3, 5);
a.add(0, "x");

Java can use a combination of the `.sublist()` method, reassignment, and the `.add()` method to replace slices. In this example the final array will be ['x', 'd', 'e']

Javascript Replace Array Slice

var a = ["a", "b", "c", "d", "e"];
a = ["x"].concat(a.slice(3, 5));

Javascript can use the `.concat()` method along with the `.slice()` method to redefine an array based on the desired slices. In this example the final array will be ['x', 'd', 'e']

C Replace Array Slice

#include <stdio.h>
...
char x[5] = {'a', 'b', 'c', 'd', 'e'};
char *n = 'x';
char *nl = '';
memcpy(x, &n, sizeof(*x));
memcpy(&x[1], &x[3], 2 * sizeof(*x));
memcpy(&x[3], &nl, sizeof(*x));
memcpy(&x[4], &nl, sizeof(*x));

C can use the `memcpy()` function along with pointers to simulate slice replacement in arrays. Note that in this case we need to manually reset the 4th and 5th positions in the array to the null byte. In this example the final array will be ['x', 'd', 'e']

PHP Replace Array Slice

$a = ["a", "b", "c", "d", "e"];
$a = array_merge(["x"], array_slice($a, 3, 5));

PHP can use a combination of the `array_merge()` and `array_slice()` functions to simulate slice replacement in arrays. In this example the final array will be ['x', 'd', 'e']

Python Slice String

a = "Cheese fries."
b = a[0:6]

Python uses the `:` operator to get a slice of a string. The number before the colon is the index of the first character of the slice, inclusive. The number after the colon is the index of the the last character of the slice, exclusive. This example slice will return 'Cheese'.

Java Slice String

String a = "Cheese fries.";
String b = a.substring(0, 6);

Java uses the `.substring()` method to get a string slice. The first argument is the index of the first character of the slice, inclusive. The second argument is the index of the the last character of the slice, exclusive. This example slice will return 'Cheese'.

Javascript Slice String

var a = "Cheese fries.";
var b = a.slice(0, 6);

Javascript uses the `.slice()` method to get a slice of a string. The first argument is the index of the first character of the slice, inclusive. The second argument is the index of the the last character of the slice, exclusive. This example slice will return 'Cheese'.

C Slice String

#include <string.h>
...
char a[] = "Cheese fries.";
int size = sizeof(a)/sizeof(a[0]);
char b[size];
memset(b, '', size);
strncpy(b, a, 6);

C can use the `strncpy()` function to copy a specified number of characters from one string to another. Note that in this case we use the `memset()` function to set all bytes of `b` to null before running `strncpy()`. This is to ensure no unwanted data from memory ends up at the end of our new string. This example slice will return 'Cheese'.

PHP Slice String

$a = "Cheese fries.";
$b = substr($a, 0, 6);

PHP uses the `substr()` function to get a slice of a string. The first argument is the index of the first character of the slice, inclusive. The second argument is the index of the the last character of the slice, exclusive. This example slice will return 'Cheese'.

Python Uppercase String

x = "hello"
x = x.upper()

Python strings can be made uppercase with the built-in `.upper()` method. Note that this does not change the string in-place.

Java Uppercase String

String x = "hello";
x = x.toUpperCase();

Java strings can be made uppercase with the `.toUpperCase()` method.

Javascript Uppercase String

var x = "hello";
x = x.toUpperCase();

Javascript strings can be made uppercase with the `.toUpperCase()` method.

C Uppercase String

int i = 0;
char str[] = "hello";

while ( str[i] ) {
    str[i] = toupper(str[i]);
    i++;
}

C uses the `toupper()` function to make a single character uppercase, so we can combine that with a loop to make a whole string uppercase.

PHP Uppercase String

strtoupper("hello");

PHP uses the `strtoupper()` function to make a string uppercase.

Python Lowercase String

x = "HELLO"
x = x.lower()

Python strings can be made lowercase with the built-in `.lower()` method. Note that this does not change the string in-place.

Java Lowercase String

String x = "HELLO";
x = x.toLowerCase();

Java strings can be made lowercase with the `.toLowerCase()` method.

Javascript Lowercase String

var x = "HELLO";
x = x.toLowerCase();

Javascript strings can be made lowercase with the `.toLowerCase()` method.

C Lowercase String

int i = 0;
char str[] = "HELLO";

while ( str[i] ) {
    str[i] = tolower(str[i]);
    i++;
}

C uses the `tolower()` function to make a single character lowercase, so we can combine that with a loop to make a whole string lowercase.

PHP Lowercase String

strtolower("HELLO");

PHP uses the `strtolower()` function to make a string lowercase.

Python Strip Whitespace

x = " Hello "
x = x.strip()

Python uses the `.strip()` method to remove whitespace from both ends of strings.

Java Strip Whitespace

String x = " Hello ";
x = x.trim();

Java uses the `.trim()` method to remove whitespace from both ends of strings.

Javascript Strip Whitespace

var x = " Hello ";
x = x.trim();

Javascript uses the `.trim()` method to remove whitespace from both ends of strings.

C Strip Whitespace

Gone fishin!

C does not have a built-in function to trim whitespace from strings.

PHP Strip Whitespace

$x = " Hello ";
$x = trim($x);

PHP uses the `trim()` function to remove whitespace from both ends of strings.

Python Split String to List / Array

x = "a b c d e"
l = x.split()

Python uses the `.split()` method to split a string into a list. By default the string is split on spaces. A string argument can be passed to the `.split()` method to specify a different character to split on.

Java Split String to List / Array

import java.util.Arrays;
...
String x = "a b c d e;";
String[] a = x.split(" ");
List<String> b = Arrays.asList(a);

Java uses the `.split()` method to split a string into an array. The argument passed to the `.split()` method specifies the character to split on. The array can be converted to a list using the `Arrays.asList()` method.

Javascript Split String to List / Array

var x = "a b c d e";
var a = x.split(" ");

Javacript uses the `.split()` method to split a string into an array. The argument passed to the `.split()` method specifies the character to split on.

C Split String to List / Array

Gone fishin!

C does not have a built-in function to split a string into a list.

PHP Split String to List / Array

$x = "a b c d e";
$a = explode(" ", $x);

PHP uses the `explode()` function to split a string into an array. The first argument passed to the `.split()` method specifies the character to split on. The second argument is the string to split.

Python Random Number

import randint from random
randint(0, 9)

Python uses the `random.randint()` function to generate a random number between two endpoints, inclusive. This example will generate a number between 0 and 9.

Java Random Number

import java.util.Random;
...
Random r = new Random();
int i = r.nextInt(10);

Java uses the `nextInt()` method from the `Random` package to generate a random integer ranging from zero to one minus the argument supplied. This example will generate a number between 0 and 9.

Javascript Random Number

var x = Math.floor(Math.random() * 10);

Javascript uses `Math.random()` to generate a floating point value between 0 and 1, which can be multiplied the desired upper bound and floored using `Math.floor()` to generate a whole integer. This example will generate a number between 0 and 9.

C Random Number

#include <stdlib.h>
#include <time.h>
...
srand(time(0));
int l = 0;
int h = 9;
int x = (rand() % (h-l+1)) + l;

C uses the `rand()` function to generate a random number. However, to generate a different number each run, it needs to be seeded using the `srand()` function. In this example we use the current time as the seed, via the `time(0)` function call. This example will generate a number between 0 and 9.

PHP Random Number

$x = rand(0, 9);

PHP uses the `rand()` function to generate a random number between two bounds. This example will generate a number between 0 and 9.

Git Init

git init

The `git init` command is used to initialize a Git repository. Whatever directory you run this command from will be configured as the root of a new Git project. Behind the scenes, `git init` creates the hidden `.git` folder in the current directory. This contains the information Git uses to track your project.

Git Clone

git clone https://website.com/repo.git

The `git clone` command is used to copy a Git repository from a remote location to a new directory on your local machine. It also creates remote tracking branches for each of the branches cloned from the source repository.

Git Add

git add <filename>

The `git add` command is used to stage a file or set of files to be included in the next commit.

Git Commit

git commit -m "Initial commit."

The format of the `git commit` command is the most commonly used. It creates a new commit on the current branch with a custom commit message. The files committed are those that were previously added to the staging area using the `git add` command.

Git Push

git push

The `git push` command copies a set of commits from the currently active local Git branch to a remote Git branch.

Git Pull

git pull

The `git pull` command copies a set of commits from a remote Git branch to the currently active local Git branch.

Git Create Branch

git branch <new-branch-name>

The `git branch ...` command is used to create a new branch in the local Git repository.

Git Checkout Branch

git checkout <branch-name>

The `git checkout` command is used to checkout an existing branch. This updates the working directory files and directories to match those of the checked out branch.

Git Merge Branch

git merge <branch-name>

The `git merge` command merges the specified branch into the currently active branch. If there are no conflicting changes between files, Git will perform the merge automatically. If there are conflicts, Git will direct the user to resolve the conflicts before completing the merge.

Git Log

git log

The `git log` command is used to show a scrollable list of commits on the currently active branch.

Git Status

git status

The `git status` command outputs some basic information about the state of the Git project. It lets you know what the currently active branch is, whether it is up to date with it's corresponding remote tracking branch, and whether any files in the working directory have been modified or added to the staging area.