Differences

This shows you the differences between two versions of the page.

--- python:virtual_environments [2014/11/25 11:33] – created kauffman
+++ python:virtual_environments [2016/06/30 11:56] (current) – [Other things you should know] kauffman
@@ Line 1: / Line 1: @@
 ====== Python Virtual Environments ======
+==== What and Why ====
+A Virtual Environment is a tool to keep the dependencies required by different projects in separate places, by creating virtual Python environments for them. It solves the “Project X depends on version 1.x but, Project Y needs 4.x” dilemma, and keeps your global site-packages directory clean and manageable. For example, you can work on a project which requires Django 1.3 while also maintaining a project which requires Django 1.0. ((http://docs.python-guide.org/en/latest/dev/virtualenvs))
+==== Other things you should know ====
+  - https://github.com/pypa/virtualenv/pull/697
+  - http://conda.pydata.org/docs/intro.html
+==== Using Virtual Environments ====
+The python virtual environment package is installed by default on most CS machines. To make sure you can do the following:
+<code>
+user@computer:~/projects$ which virtualenv
+/usr/bin/virtualenv
+</code>
+==== Creating a new project ====
+<code>
+user@hester:~/projects$ virtualenv --no-site-packages exampleproject
+The --no-site-packages flag is deprecated; it is now the default behavior.
+New python executable in exampleproject/bin/python
+Installing
+distribute................................................................................done.
+Installing pip...............done.
+</code>
+<code>
+user@computer:~/projects$ ls -l exampleproject/
+total 4
+drwxrwxr-x 2 user group 4096 Nov 25 10:16 bin
+drwxrwxr-x 2 user group   30 Nov 25 10:16 include
+drwxrwxr-x 3 user group   30 Nov 25 10:16 lib
+drwxrwxr-x 2 user group   56 Nov 25 10:16 local
+</code>
+<code>
+user@computer:~/projects$ cd exampleproject/
+</code>
+==== Activate ====
+Now you need to activate your virtual environment. This will setup some path variables to make the environments bin and lib directory to be the default.
+<code>
+user@computer:~/projects/exampleproject$ source bin/activate
+(exampleproject)user@computer:~/projects/exampleproject$
+</code>
+==== Installing Modules ====
+After activating the virtual environment you will notice that your prompt changed a little. This is not the only thing that has changed. Your $PATH and default python have changed as well (just checkout the bin/activate script to see what else it does).
+Notice that the 'bin' directory in your virtual environment has been prepended to $PATH and the python and pip executables are inside the bin directory.
+<code>
+(exampleproject)user@computer:~/projects/exampleproject$ echo $PATH
+/home/user/projects/exampleproject/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games
+</code>
+<code>
+(exampleproject)user@computer:~/projects/exampleproject$ which python
+/home/user/projects/exampleproject/bin/python
+</code>
+<code>
+(exampleproject)user@computer:~/projects/exampleproject$ which pip
+/home/user/projects/exampleproject/bin/pip
+</code>
+So to actually install your own python modules you can use 'pip' or 'easy_install' to do so:
+<code>
+(exampleproject)user@computer:~/projects/exampleproject$ pip install docopt
+Downloading/unpacking docopt
+  Downloading docopt-0.6.2.tar.gz
+  Running setup.py egg_info for package docopt
+Installing collected packages: docopt
+  Running setup.py install for docopt
+Successfully installed docopt
+Cleaning up...
+</code>
+Notice where docopt was installed (~/projects/exampleproject/local/lib/python2.7/site-packages):
+<code>
+(exampleproject)user@computer:~/projects/exampleproject$ ls -l local/lib/python2.7/site-packages/docopt*
+-rw------- 1 user group 19946 Mar  8 23:12 local/lib/python2.7/site-packages/docopt.py
+-rw------- 1 user group 26140 Mar  8 23:12 local/lib/python2.7/site-packages/docopt.pyc
+local/lib/python2.7/site-packages/docopt-0.6.2-py2.7.egg-info:
+total 40
+-rw------- 1 user group     1 Mar  8 23:12 dependency_links.txt
+-rw------- 1 user group    86 Mar  8 23:12 installed-files.txt
+-rw------- 1 user group 21525 Mar  8 23:12 PKG-INFO
+-rw------- 1 user group   651 Mar  8 23:12 SOURCES.txt
+-rw------- 1 user group     7 Mar  8 23:12 top_level.txt
+</code>
+==== Deactivate ====
+To deactivate or stop working on your environment use the function that gets sourced when you activate your environment:
+<code>
+(exampleproject)user@computer:~/projects/exampleproject$ deactivate
+user@computer:~/projects/exampleproject$
+</code>