[python] Python virtualenv questions

I'm using VirtualEnv on Windows XP. I'm wondering if I have my brain wrapped around it correctly:

I ran virtualenv ENV and it created C:\WINDOWS\system32\ENV. I then changed my PATH variable to include C:\WINDOWS\system32\ENV\Scripts instead of C:\Python27\Scripts. Then, I checked out Django into C:\WINDOWS\system32\ENV\Lib\site-packages\django-trunk, updated my PYTHON_PATH variable to point the new Django directory, and continued to easy_install other things (which of course go into my new C:\WINDOWS\system32\ENV\Lib\site-packages directory).

I understand why I should use VirtualEnv so I can run multiple versions of Django, and other libraries on the same machine, but does this mean that to switch between environments I have to basically change my PATH and PYTHON_PATH variable? So, I go from developing one Django project which uses Django 1.2 in an environment called ENV and then change my PATH and such so that I can use an environment called ENV2 which has the dev version of Django?

Is that basically it, or is there some better way to automatically do all this (I could update my path in Python code, but that would require me to write machine-specific code in my application)?

Also, how does this process compare to using VirtualEnv on Linux (I'm quite the beginner at Linux).

in my project wsgi.py file i have this code (it works with virtualenv,django,apache2 in windows and python 3.4)

import os
import sys
DJANGO_PATH = os.path.join(os.path.abspath(os.path.dirname(__file__)),'..')
sys.path.append(DJANGO_PATH)
sys.path.append('c:/myproject/env/Scripts')
sys.path.append('c:/myproject/env/Lib/site-packages')
activate_this = 'c:/myproject/env/scripts/activate_this.py'
exec(open(activate_this).read())
from django.core.wsgi import get_wsgi_application
os.environ.setdefault("DJANGO_SETTINGS_MODULE", "myproject.settings")
application = get_wsgi_application()

in virtualhost file conf i have

<VirtualHost *:80>
    ServerName mysite
    WSGIScriptAlias / c:/myproject/myproject/myproject/wsgi.py
    DocumentRoot c:/myproject/myproject/
    <Directory  "c:/myproject/myproject/myproject/">
       Options +Indexes +FollowSymLinks +MultiViews
       AllowOverride All
      Require local
   </Directory>
</VirtualHost>

Yes basically this is what virtualenv do , and this is what the activate command is for, from the doc here:

activate script

In a newly created virtualenv there will be a bin/activate shell script, or a Scripts/activate.bat batch file on Windows.

This will change your $PATH to point to the virtualenv bin/ directory. Unlike workingenv, this is all it does; it's a convenience. But if you use the complete path like /path/to/env/bin/python script.py you do not need to activate the environment first. You have to use source because it changes the environment in-place. After activating an environment you can use the function deactivate to undo the changes.

The activate script will also modify your shell prompt to indicate which environment is currently active.

so you should just use activate command which will do all that for you:

> \path\to\env\bin\activate.bat

After creating virtual environment copy the activate.bat file from Script folder of python and paste to it your environment and open cmd from your virtual environment and run activate.bat file.enter image description here

on Windows I have python 3.7 installed and I still couldn't activate virtualenv from Gitbash with ./Scripts/activate although it worked from Powershell after running Set-ExecutionPolicy Unrestricted in Powershell and changing the setting to "Yes To All".

I don't like Powershell and I like to use Gitbash, so to activate virtualenv in Gitbash first navigate to your project folder, use ls to list the contents of the folder and be sure you see "Scripts". Change directory to "Scripts" using cd Scripts, once you're in the "Scripts" path use . activate to activate virtualenv. Don't forget the space after the dot.