Python Cheatsheet

python-cheatsheet.md

Python Cheatsheet

Python Version Manager

Use Homebrew to install pyenv and pyenv-virtualenv:

$ brew install pyenv
$ brew install pyenv-virtualenv

Add the following to your ~/.bash_profile or equivalent shell initialization script:

eval "$(pyenv init -)"
eval "$(pyenv virtualenv-init -)"

Then source ~/.bash_profile and install the version of Python you need:

$ pyenv install 2.7.13
$ pyenv global 2.7.13

List Available Python Versions

To see a list of avaiable Python versions:

$ pyenv install --list

Project Specific Python Environments

To create a Python environment specific to a project use the pyenv virtualenv command with the version of Python you want to use and the name of your virtual environment:

$ cd project-name
$ pyenv virtualenv 2.7.13 project-name
$ pyenv activate project-name
... you doing lots of work
$ pyenv deactivate

Managing Dependencies

Adding Dependencies to your VirtualEnv

Add your dependency using pip install:

$ pip install fabric

Freezing Dependencies for your Project

Python use requirements.txt to define a project's dependencies. You can use pip freeze to generate that file:

$ pip freeze > requirements.txt
$ git add requirements.txt

Installing Dependencies for your Projcet

To install dependencies listed in requirements.txt use the pip install command:

$ pip install -r requirements.txt

Task Automation

Use Fabric to automate tasks and deployments.

Add Fabric to your Project

First add fabric with the pip install command:

$ pip install fabric

Define Tasks in fabfile.py:

Create a file named fabfile.py and define Tasks in it:

from fabric.api import task
from fabric.operations import local

@task(alias='s', default=True)
def server():
    """Start a local web server on port 4567"""
    local('python server.py')

The local command is used to run tasks on your local machine.

Running Tasks

To run a task use the fab command followed by the name of the task:

$ fab server
[localhost] local: python server.py
Serving HTTP on 0.0.0.0 port 4567 ...

Listing Tasks

To list the tasks available in your Fabfile, use the --list or -l command-line option:

$ fab -l
Available commands:

    s       Start a local web server on port 4567
    server  Start a local web server on port 4567