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_PYTHONValue: 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...

1. Start > in the search type in environment select "Edit environment variables to your account"1

2. Scroll down to Path, select path, click edit.

3. 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;

4. Navigate to the Python27 folder in C:\ and rename a copy of python.exe to python2.exe

5. Navigate to the Python34 folder in C:\ and rename a copy of python.exe to python3.exe

6. Test: open up commmand prompt and type python2 ....BOOM! Python 2.7.6. exit out.

7. 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