Date Tags Python

I am always forgetting how to do this and so I thought I would throw this quick write-up together about how you can get Python 2 and 3 to play nicely together on Windows 7 and higher.

To run Python 2 and 3 side by side on Windows

  • Install Python 2 - 64bit with default options (DO NOT check the option to add anything to the path)

  • Install Python 3 - 64bit with default options (DO NOT check the option to add anything to the path)

Python 2 and 3 will be installed with their default locations and you will notice that typing python at the command line will now do nothing. This is fine.

The installers will install the Python launcher, which is two executables into your Windows directory:

Python 2

To start the Python 2 interpreter

py

To run Python 2 pip

py -m pip list

To install Python 2 module

py -m pip install flask

To run Python 2 script

py main.py

To get version number

py --version

Python 3

To start the Python 3 interpreter

py -3

To run Python 3 pip

py -3 -m pip list

To install Python 3 module

py -3 -m pip install flask

To run Python 3 script

py -3 main.py

To get version number

py -3 --version

Create a virtual environment on the CLI with Python 3

# first intall it
py -3 -m pip install virtualenv

# then create it
py -3 -m virtualenv venv

# activate it
venv\Scripts\activate.bat

Letting py determine the proper interpreter to run

use #!python2 or #!python3 at the top of your script to let py.exe determine whether to launch Python 2 or Python 3. Then you can launch either with something like py script.py

Great resources that helped me solve this issue

How do I run python 2 and 3 in windows 7?

How to use pip with python 3.4 on windows?


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