How to install both Python 2.x and Python 3.x in Windows
I found that the formal way to do this is as follows:
Just install two (or more, using their installers) versions of Python on Windows 7 (for me work with 3.3 and 2.7).
Follow the instuctions below, changing the parameters for your needs.
Create the following environment variable (to default on double click):
Name: PY_PYTHON
Value: 3
To launch a script in a particular interpreter, add the following shebang (beginning of script):
#! python2
To execute a script using a specific interpreter, use the following prompt command:
> py -2 MyScript.py
To launch a specific interpreter:
> py -2
To launch the default interpreter (defined by the PY_PYTHON variable):
> py
Resources
Documentation: Using Python on Windows
PEP 397 - Python launcher for Windows
What I did was download both 2.7.6 and 3.3.4. Python 3.3.4 has the option to add the path to it in the environment variable so that was done. So basically I just manually added Python 2.7.6.
How to...
Start > in the search type in environment select "Edit environment variables to your account"1
Scroll down to Path, select path, click edit.
Add C:\Python27; so you should have paths to both versions of Python there, but if you don't this you can easily edit it so that you do..... C:\Python27;C:\Python33;
Navigate to the Python27 folder in C:\ and rename a copy of python.exe to python2.exe
Navigate to the Python34 folder in C:\ and rename a copy of python.exe to python3.exe
Test: open up commmand prompt and type python2 ....BOOM! Python 2.7.6. exit out.
Test: open up commmand prompt and type python3 ....BOOM! Python 3.4.3. exit out.
Note: (so as not to break pip commands in step 4 and 5, keep copy of python.exe in the same directory as the renamed file)
I have multiple versions in windows. I just change the exe name of the version I'm not defaulting to.
python.exe --> python26.exe
pythonw.exe --> pythonw26.exe
As for package installers, most exe installers allow you to choose the python install to add the package too. For manual installation check out the --prefix option to define where the package should be installed:
http://docs.python.org/install/index.html#alternate-installation-windows-the-prefix-scheme