Editing Virtual Environments with Python

[[Category:Python]] [[Category:Web Development]]
== Overview ==

Mac OS X Yosemite comes with Python 2.7 installed. 

After installing Python 3.4, the `python` command still invokes Python 2.x. This can be overcome by using `python3` instead.

Similarly, the `pip` command invokes pip that was installed with Python 2.x. So, `sudo pip install [package_name]` will install for Python 2.x and leave Python 3.x unchanged. `pip3` can be used to update Python 3.x on the command line. 

== Creating virtual environments on Mac ==

First, install `virtualenv` if it is not already installed: `sudo pip(3) install virtualenv`. A new terminal shell is required to have the `virtualenv` command available.<ref>[http://stackoverflow.com/a/10763461 Build a `virtualenv` of python 3] - Stack Overflow</ref>

<syntaxhighlight lang="bash">
$ virtualenv -p /Library/Frameworks/Python.framework/Versions/3.4/bin/python3 py3env
$ source py3env/bin/activate
$ pip install package-name
</syntaxhighlight>

Once the virtualenv has been created it can be activated with the 2nd command:

<syntaxhighlight lang="bash">
$ source ~/py3env/bin/activate
</syntaxhighlight>


To find the path to Python 3.x: 

<syntaxhighlight lang="bash">
$ which python3
</syntaxhighlight>

''N.B. Packages will probably have to be installed for new virtual environments, e.g. django, etc.''

== Using a virtual environment in PyCharm ==

* '''File''' > '''Default Settings...''' > '''Default Project''' > '''Project Interpreter'''
** Click the gear icon to the right of '''Project Interpreter:'''
*** Choose '''Add Local''' for existing virtualenv, or '''Create VirtualEnv''' for a new one
*** Select the virtualenv, and apply the changes.<ref>[https://www.jetbrains.com/pycharm/help/creating-virtual-environment.html Creating Virtual Environment] - PyCharm 4.5.3 Help</ref>
 
== References ==
<references />
* [http://hackercodex.com/guide/python-development-environment-on-mac-osx/#virtualenv Python Development Environment on Mac OS X Yosemite 10.10: virtualenv] - Hacker Codex