When you try to run the command ( py -3 main.py ) does it say "py" is not an internal or external command, operable program, or batch file?

Question

Python

At the same time, pip and python work correctly.

Answer 1

python3 main.py

Answer 2

Since py.exe is installed (along with Python) in C:\Windows, which is explicit in Path, then you most likely did not install it (if installed, it is visible in the Control Panel in the list of installed programs like Python Launcher, it seems)