How does the Windows Python Launcher (py.exe) find the python executable(s)?

Question

I'm trying to use the Windows Python Launcher (py.exe) for the first time. I run python in a command shell but the launcher, running in the same shell, can't find any version of python.exe to run:

where python                                          
C:\Python38\python.exe                                  
py --list                                             
Installed Pythons found by py Launcher for Windows      
No Installed Pythons Found!

Obviously there is something missing in my configuration but I'm at a loss as to what. I've been digging into the registery and have located keys in:

HKEY_LOCAL_MACHINE/SOFTWARE/Wow6432Node/Python/PyLauncher   
HKEY_LOCAL_MACHINE/SOFTWARE/Wow6432Node/Python/PythonCore

but there isn't anything that references any executables.

Any help appreciated!

At first I was going to write a pithy comment telling you to read the documentation and how to find it. But then I realized that the information there is actually not very useful for your specific question. Even so, this question seems like a better fit for superuser.com (I couldn't find a duplicate there, either). On my own machine, the behaviour is the reverse: py finds my Python installations that are not on the PATH, but where python comes up empty-handed and python only works inside a venv. — Karl Knechtel
– Karl Knechtel, Commented Mar 26, 2021 at 23:08

Jean-François Bourdon · Accepted Answer · 2023-10-25 19:50:12Z

4

You were on the right path. In your case, you would need to add the following entries in the registry:

[HKEY_CURRENT_USER\SOFTWARE\Python\PythonCore\3.8]

[HKEY_CURRENT_USER\SOFTWARE\Python\PythonCore\3.8\InstallPath]
@="C:\\python38\\"
"ExecutablePath"="C:\\Python38\\python.exe"
"WindowedExecutablePath"="C:\\Python38\\pythonw.exe"

Also answered in py launcher does not find my Python 2.7

edited Oct 25, 2023 at 19:50

answered Nov 3, 2022 at 15:36

Jean-François Bourdon

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