Tutorial by Examples: g

Python 2.x2.7 To import a module through a function call, use the importlib module (included in Python starting in version 2.7): import importlib random = importlib.import_module("random") The importlib.import_module() function will also import the submodule of a package directly: c...

To share files or to host simple websites(http and javascript) in your local network, you can use Python's builtin SimpleHTTPServer module. Python should be in your Path variable. Go to the folder where your files are and type: For python 2: $ python -m SimpleHTTPServer <portnumber> For p...

If you are building a function that may be heavy on the processor (either clientside or serverside) you may want to consider a memoizer which is a cache of previous function executions and their returned values. This allows you to check if the parameters of a function were passed before. Remember, p...

The specifier override has a special meaning in C++11 onwards, if appended at the end of function signature. This signifies that a function is Overriding the function present in base class & The Base class function is virtual There is no run time significance of this specifier as is mainl...

Trailing spaces \s*$: This will match any (*) whitespace (\s) at the end ($) of the text Leading spaces ^\s*: This will match any (*) whitespace (\s) at the beginning (^) of the text Remarks \s is a common metacharacter for several RegExp engines, and is meant to capture whitespace characters (...

child.py import time def main(): print "starting work" time.sleep(1) print "work work work work work" time.sleep(1) print "done working" if __name__ == '__main__': main() parent.py import os def main(): for i in range(5):...

Pass dynamic inventory to ansible-playbook: ansible-playbook -i inventory/dyn.py -l targethost my_playbook.yml python inventory/dyn.py should print out something like this: { "_meta": { "hostvars": { "10.1.0.10": { "ansible_user": ...

Available in Django 1.9+ from django.contrib.postgres.fields import JSONField from django.db import models class IceCream(models.Model): metadata = JSONField() You can add the normal **options if you wish. ! Note that you must put 'django.contrib.postgres' in INSTALLED_APPS in your s...

Pass data in native Python form, for example list, dict, str, None, bool, etc. IceCream.objects.create(metadata={ 'date': '1/1/2016', 'ordered by': 'Jon Skeet', 'buyer': { 'favorite flavor': 'vanilla', 'known for': ['his rep on SO', 'writing a book'] }, ...

IceCream.objects.filter(metadata__ordered_by='Guido Van Rossum')

Get all ice cream cones that were ordered by people liking chocolate: IceCream.objects.filter(metadata__buyer__favorite_flavor='chocolate') See the note in the "Remarks" section about chaining queries.

An integer will be interpreted as an index lookup. IceCream.objects.filter(metadata__buyer__known_for__0='creating stack overflow') See the note in the "Remarks" section about chaining queries.

This assumes you have a twilio account and have purchased/reserved a phone number... If you are using bundler add the following line to your Gemfile to include twilio-ruby in your project: gem 'twilio-ruby' otherwise enter gem install twilio-ruby on the command line. You might need sudo if you'...

You can create a TCP server using the socketserver library. Here's a simple echo server. Server side from sockerserver import BaseRequestHandler, TCPServer class EchoHandler(BaseRequestHandler): def handle(self): print('connection from:', self.client_address) while True:...

A UDP server is easily created using the socketserver library. a simple time server: import time from socketserver import BaseRequestHandler, UDPServer class CtimeHandler(BaseRequestHandler): def handle(self): print('connection from: ', self.client_address) # Get message and cli...

The vast majority of Python memory management is handled with reference counting. Every time an object is referenced (e.g. assigned to a variable), its reference count is automatically increased. When it is dereferenced (e.g. variable goes out of scope), its reference count is automatically decreas...

The only time the garbage collector is needed is if you have a reference cycle. The simples example of a reference cycle is one in which A refers to B and B refers to A, while nothing else refers to either A or B. Neither A or B are accessible from anywhere in the program, so they can safely be dest...

To disassemble a Python module, first this has to be turned into a .pyc file (Python compiled). To do this, run python -m compileall <file>.py Then in an interpreter, run import dis import marshal with open("<file>.pyc", "rb") as code_f: code_f.read(8) # M...

Trap expressions don't have to be individual functions or programs, they can be more complex expressions as well. By combining jobs -p and kill, we can kill all spawned child processes of the shell on exit: trap 'jobs -p | xargs kill' EXIT

The typing.TypeVar is a generic type factory. It's primary goal is to serve as a parameter/placeholder for generic function/class/method annotations: import typing T = typing.TypeVar("T") def get_first_element(l: typing.Sequence[T]) -> T: """Gets the first ele...