# Self contained environment for programming languages

language_development_envs.md

Isolating development environments by using language tools

RVM for Pythonistas, Virtualenv for Rubyists

For Python Developers: virtualenv, virtualenvwrapper or Buildout

Note: envs = environments

For Ruby Developers: rvm

Installation

Python

Info	Command
Install pip	$ sudo pip install virtualenvwrapper
Create dir. to contain virtual envs.	$HOME/.virtualenvs: OR mkdir ~/.virtualenvs

Edit your $HOME/bash_profile file & add these lines:

	export WORKON_HOME=$HOME/.virtualenvs
	export PIP_VIRTUALENV_BASE=$WORKON_HOME
	export PIP_RESPECT_VIRTUALENV=true

Source It: source ~/.bash_profile

Ruby

First, make sure Git is installed on your system.

 bash <<( curl http://rvm.beginrescueend.com/releases/rvm-install-head )

Edit your $HOME/.bash_profile file & add this line at the very end:

	[[ -s "$HOME/.rvm/scripts/rvm" ]] && . "$HOME/.rvm/scripts/rvm" 

Source It: source ~/.rvm/scripts/rvm

Managing Multiple Interpreters

Python

You have to install the different Python versions on your system (via package manager).When you will create a virtual environment with virtualenv, you will pass the interpreter path of the desired Python version as -p argument of mkvirtualenv command.

	$ mkvirtualenv -p /opt/local/bin/python3 myproject

Ruby

RVM compiles & installs the desired Ruby interpreter & Ruby version in the current user directory. It supports MRI/YARV, Rubinius, JRuby, Ruby Enterprise Edition, MagLev, IronRuby, MacRuby & GoRuby. This can be achieved in a single one command.

Info	Command
List available interpreters & versions	$ rvm list known
Install different versions	$ rvm install RUBY_VERSION
List Installed versions	$ rvm list
Switch between interpreters	$ rvm use RUBY_VERSION
Set up the default interpreter	$ rvm --default use X.X.X
Switch back to default system interpreter	$ rvm use system

Managing Multiple Environments

Python

Generally, with virtualenv, you create one environment per project and/or project stage (development, testing, staging, production, etc).

Info	Command
themkvirtualenv command	$ mkvirtualenv --no-site-packages PROJECT_NAME
	$ mkvirtualenv --no-site-packages superdjango

The --no-site-packages option removes the standard site-packages directory from the environment sys.path. Use this option if you want more isolation to avoids dealing with system packages conflicts. As seen above, you can specify the Python version with the -p option:

$ mkvirtualenv --no-site-packages -p /opt/local/bin/python3 PROJECT_NAME

Add export PIP_RESPECT_VIRTUALENV=true into $HOME/.bash_profile file, when your environment is active, pip auto-installs packages in this environment; auto-switch to this environment instantly.

Info	Command
Install Packages to env	$ pip install PACKAGE OR $ pip install Django
The -E option	$ pip install -E ENVIRONMENT_NAME PACKAGE
	$ pip install -E superdjango Django
List available envs	Use the workon command.
Activate env	$ workon ENVIRONMENT_NAME OR $ workon superdjango
Create virtual env	mkvirtualenv command
Deactivate current env	Use thedeactivate command
Delete a virtual env	$ rmvirtualenv ENVIRONMENT_NAME OR $ rmvirtualenv superdjango

Ruby

Where virtualenv has environments, RVM has gemsets. Interpreters & packages are all separated & self-contained from system & from each other. Creating a virtual env with virtualenv is creating a gemset with RVM; you create one gemset per project and/or project stage (development, testing, staging, production, etc).

Info	Command
Install Gemset	$ rvm use RUBY_VERSION@GEMSET_NAME --create
	$ rvm use 1.9.2@myproject --create
Equivalent to	$ rvm use 1.9.2
	$ rvm gemset create myproject
	$ rvm gemset use myproject
Install packages to gemset	$ gem install PACKAGE
Know path of dir.	$ rvm gemdir command
Deleting a gemset	$ rvm gemset delete GEMSET_NAME OR $ rvm gemset delete myproject
Empty/Remove gemset	$ rvm gemset empty GEMSET_NAME OR $ rvm gemset empty myproject

Managing project dependencies

Python

With pip & virtualenv. Just have to create a text file containing package names (& optionally package versions) & give this file to pip via the -r option. For “superdjango” project, created a requirements.txt file to start project with Django 1.2.x & South support.

Inside requirements.txt:

	Django >= 1.2
	South == 0.7.2

Created environment:

	$ mkvirtualenv --no-site-packages superdjango

Plus install project dependencies:

	$ pip install -r /path/to/my/requirements.txt

This will install the latest Django 1.2 version & South 0.7.2 into virtual environment.

Ruby

With RVM, RubyGem & Bundler. Where pip has requirements files, Bundler has Gemfile files. Create a dedicated gemset for Pjt:

	$ rvm use 1.9.2@myproject --create
		# 	OR	#
	$ rvm use 1.9.2
  	rvm gemset create myproject
  	rvm gemset use myproject

Install Bundler into gemset:

	$ gem install bundler

Created a directory for project:

	$ cd /path/to/my/workspace
  	mkdir myproject

Go to directory & create an empty Gemfile file:

	$ cd myproject
  	bundle init

Edit the Gemfile file & add dependencies:

	$ source "http://rubygems.org"
  	gem "sinatra", "~> 0.9.0"
  	gem "rack-cache"
  	bundle install