When developing in Python I enjoy using Sublime Text, especially its ability to run/build right from Sublime by simply pressing COMMAND+B. Meaning that I dont have to go out of the editor to the terminal to run the Python program.

Sample Python Program:

#!/usr/bin/env python

print "Hello World"

In sublime, I can program, run the program and see the result, increasing my productivity:

But what if I want to run a Python Virtual Environment and its benefits (see developing-in-python-using-python-virtual-environments).
Once the virtual environment is activated your terminal will use the Python Virtual Environment just fine, but Sublime Text will not, it will continue to use the system-wide Python environment by default.

Example: Having a Python module (e.g. IPy) installed in your virtual environment, but not system-wide, and having the Python virtual environment active:

# Python code:

#!/usr/bin/env python

import IPy

print "Hello World"

# Running from terminal – (OK):

$ python hello.py
Hello World

# Running from Sublime – (NOT OK):

To make Sublime Text use the virtual environment you need to create a Sublime project and edit its properties to use the Virtual Env.

# Create Sublime Project
Go to Project -> Save Project As…
// I named mine blog.sublime-project

# Edit project properties by editing the file in sublime to be as follows:
Note:
Remember the name: label as this is how you will use the build with… option
The shell_cmd: label is the command that will run when you build. It is far from perfect as you have to hardcode the Python program in the configuration, but at least works.

{
	"folders":
	[
		{
			"path": "."
		}
	],
	"virtualenv": "env",
	"build_systems": [
	  {
	  "name": "PYTHON_VENV",
	  "shell_cmd": "env/bin/python hello.py"
	  }
 	] 
}

# Prepare Sublime to use your new build system:
Tools -> Build Systems -> PYTHON_VENV

# Now you can now continue to code and use COMMAND+B to build/run your programs without leaving your Sublime Text editor: