Tutorial by Examples: en

Exponentiation can be used by using the builtin pow-function or the ** operator: 2 ** 3 # 8 pow(2, 3) # 8 For most (all in Python 2.x) arithmetic operations the result's type will be that of the wider operand. This is not true for **; the following cases are exceptions from this rule: B...

The math-module contains another math.pow() function. The difference to the builtin pow()-function or ** operator is that the result is always a float: import math math.pow(2, 2) # 4.0 math.pow(-2., 2) # 4.0 Which excludes computations with complex inputs: math.pow(2, 2+0j) TypeErro...

Both the math and cmath-module contain the Euler number: e and using it with the builtin pow()-function or **-operator works mostly like math.exp(): import math math.e ** 2 # 7.3890560989306495 math.exp(2) # 7.38905609893065 import cmath cmath.e ** 2 # 7.3890560989306495 cmath.exp(2) # (...

The math module contains the expm1()-function that can compute the expression math.e ** x - 1 for very small x with higher precision than math.exp(x) or cmath.exp(x) would allow: import math print(math.e ** 1e-3 - 1) # 0.0010005001667083846 print(math.exp(1e-3) - 1) # 0.0010005001667083846 p...

Supposing you have a class that stores purely integer values: class Integer(object): def __init__(self, value): self.value = int(value) # Cast to an integer def __repr__(self): return '{cls}({val})'.format(cls=self.__class__.__name__, ...

All built-in collections in Python implement a way to check element membership using in. List alist = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] 5 in alist # True 10 in alist # False Tuple atuple = ('0', '1', '2', '3', '4') 4 in atuple # False '4' in atuple # True String astring = 'i am a s...

Sorted sequences allow the use of faster searching algorithms: bisect.bisect_left()1: import bisect def index_sorted(sorted_seq, value): """Locate the leftmost value exactly equal to x or raise a ValueError""" i = bisect.bisect_left(sorted_seq, value) ...

Searching in nested sequences like a list of tuple requires an approach like searching the keys for values in dict but needs customized functions. The index of the outermost sequence if the value was found in the sequence: def outer_index(nested_sequence, value): return next(index for index, ...

from itertools import imap from future_builtins import map as fmap # Different name to highlight differences image = [[1, 2, 3], [4, 5, 6], [7, 8, 9]] list(map(None, *image)) # Out: [(1, 4, 7), (2, 5, 8), (3, 6, 9)] list(fmap(None, *image)) # Out: [(1, 4, 7), (2, 5, 8),...

Abbreviated from https://blogs.dropbox.com/developers/2013/07/using-oauth-2-0-with-the-core-api/: Step 1: Begin authorization Send the user to this web page, with your values filled in: https://www.dropbox.com/oauth2/authorize?client_id=<app key>&response_type=code&redirect_uri=<...

If your latest commit is not published yet (not pushed to an upstream repository) then you can amend your commit. git commit --amend This will put the currently staged changes onto the previous commit. Note: This can also be used to edit an incorrect commit message. It will bring up the default...

This is an example of dereferencing a NULL pointer, causing undefined behavior. int * pointer = NULL; int value = *pointer; /* Dereferencing happens here */ A NULL pointer is guaranteed by the C standard to compare unequal to any pointer to a valid object, and dereferencing it invokes undefined...

int i = 42; i = i++; /* Assignment changes variable, post-increment as well */ int a = i++ + i--; Code like this often leads to speculations about the "resulting value" of i. Rather than specifying an outcome, however, the C standards specify that evaluating such an expression produc...

int foo(void) { /* do stuff */ /* no return here */ } int main(void) { /* Trying to use the (not) returned value causes UB */ int value = foo(); return 0; } When a function is declared to return a value then it has to do so on every possible code path through it. Undefined beh...

#include <stdio.h> #include <stdlib.h> #include <string.h> int main(int argc, char **argv) { /* Exit if no second argument is found. */ if (argc != 2) { puts("Argument missing."); return EXIT_FAILURE; } size_t len = str...

To access the event object, include an event parameter in the event listener callback function: var foo = document.getElementById("foo"); foo.addEventListener("click", onClick); function onClick(event) { // the `event` parameter is the event object // e.g. `event.type`...

In order to test the beginning and ending of a given string in Python, one can use the methods str.startswith() and str.endswith(). str.startswith(prefix[, start[, end]]) As it's name implies, str.startswith is used to test whether a given string starts with the given characters in prefix. >...

Strict mode can be applied on entire scripts by placing the statement "use strict"; before any other statements. "use strict"; // strict mode now applies for the rest of the script Strict mode is only enabled in scripts where you define "use strict". You can combin...

try { StyledDocument doc = new DefaultStyledDocument(); doc.insertString(0, "This is the beginning text", null); doc.insertString(doc.getLength(), "\nInserting new line at end of doc", null); MutableAttributeSet attrs = new SimpleAttributeSet(); StyleCons...

try { JTextPane pane = new JTextPane(); StyledDocument doc = new DefaultStyledDocument(); doc.insertString(0, "Some text", null); pane.setDocument(doc); //Technically takes any subclass of Document } catch (BadLocationException ex) { //hand...