Tutorial by Examples: l

SQLite is a C library that is typically compiled directly into the application by downloading the source code of the latest version, and adding the sqlite3.c file to the project. Many script languages (e.g., Perl, Python, Ruby, etc.) and frameworks (e.g., Android) have support for SQLite; this is d...

A syntactic extension that lets you write \case in place of \arg -> case arg of. Consider the following function definition: dayOfTheWeek :: Int -> String dayOfTheWeek 0 = "Sunday" dayOfTheWeek 1 = "Monday" dayOfTheWeek 2 = "Tuesday" dayOfTheWeek 3 = "W...

A typical use case for a filter is to remove values from an array. In this example we pass in an array and remove any nulls found in it, returning the array. function removeNulls() { return function(list) { for (var i = list.length - 1; i >= 0; i--) { if (typeof list[i...

Another use case for filters is to format a single value. In this example, we pass in a value and we are returned an appropriate true boolean value. function convertToBooleanValue() { return function(input) { if (typeof input !== 'undefined' && input !== null ...

:root { --red: #b00; --blue: #4679bd; --grey: #ddd; } .Bx1 { color: var(--red); background: var(--grey); border: 1px solid var(--red); }

:root { --W200: 200px; --W10: 10px; } .Bx2 { width: var(--W200); height: var(--W200); margin: var(--W10); }

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 (...

The <datalist> tag specifies a list of pre-defined options for an <input> element. It provide an "autocomplete" feature on <input> elements. Users will see a drop-down list of options as they write. <input list="Languages"> <datalist id="Langua...

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')

Python 3.x3.0 Python 3 added a new keyword called nonlocal. The nonlocal keyword adds a scope override to the inner scope. You can read all about it in PEP 3104. This is best illustrated with a couple of code examples. One of the most common examples is to create function that can increment: def c...

To iterate all files, including in sub directories, use os.walk: import os for root, folders, files in os.walk(root_dir): for filename in files: print root, filename root_dir can be "." to start from current directory, or any other path to start from. Python 3.x3.5 If ...

Using subprocess.Popen give more fine-grained control over launched processes than subprocess.call. Launching a subprocess process = subprocess.Popen([r'C:\path\to\app.exe', 'arg1', '--flag', 'arg']) The signature for Popen is very similar to the call function; however, Popen will return immedi...

vimtutor is an interactive tutorial covering the most basic aspects of text editing. On UNIX-like system, you can start the tutorial with: $ vimtutor On Windows, “Vim tutor” can be found in the “Vim 7.x” directory under “All Programs” in the Windows menu. See :help vimtutor for further details...

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'...

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...

Removing a variable name from the scope using del v, or removing an object from a collection using del v[item] or del[i:j], or removing an attribute using del v.name, or any other way of removing references to an object, does not trigger any destructor calls or any memory being freed in and of itsel...