Multiple Python versions on Windows

Hi πŸ‘‹

In this short article I will show you two ways of changing Python versions on Windows. It is useful when you have installed multiple Python versions on your system and want to run a specific version from the terminal.

For example, if we have the following versions installed:

We can use either the Python Launcher py to run Python or the python command.

Python Launcher

To list installed Python versions with Python launcher we can use the py -0 command.

@nutiu ➜ ~ py -0
Installed Pythons found by C:\WINDOWS\py.exe Launcher for Windows
 -3.10-64 *
 -3.7-64

@nutiu ➜ ~ py
Python 3.10.3 (tags/v3.10.3:a342a49, Mar 16 2022, 13:07:40) [MSC v.1929 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>>

The default version has a star next to it. If we run a simple py command, we’ll get a prompt to Python 3.10. To change the default version all we need to do is to set the environment variable PY_PYTHON to the desired version.

@nutiu ➜ ~ $env:PY_PYTHON = "3.7"
@nutiu ➜ ~ py -0
Installed Pythons found by C:\WINDOWS\py.exe Launcher for Windows
 -3.10-64
 -3.7-64 *
@nutiu ➜ ~ py
Python 3.7.0 (v3.7.0:1bf9cc5093, Jun 27 2018, 04:59:51) [MSC v.1914 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>>

Using the Python command

If you prefer running Python using the full command then you’ll get the Python version which has higher precedence in your path, for example if I run python on my machine I will get:

@nutiu ➜ ~ python
Python 3.10.3 (tags/v3.10.3:a342a49, Mar 16 2022, 13:07:40) [MSC v.1929 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>>

We can change the order by going to: My PC -> Advanced System Settings -> Environment Variables

Select path from User variables and click Edit…

Python 3.10 has higher precedence in path because it is above Python 3.7. If we want to change the order, we need to select the folders referencing Python37 and click Move Up until they are above Python 3.10

Restarting your terminal and running python again should run your desired Python version.

Thanks for reading! 🍻

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