"System cannot find path specified"(Geany)

[snippsat]

Your Path look okay as python works from cmd,also look at Python 3.9/3.8 and pip installation under Windows
Go into Build ➡ Set Build Commands.
Then last Execute Commands

python "%f"
# Or not close window
python -i "%f"

Alternative for a better REPL install ptpython
Then in Geany:

ptpython -i "%f"

So if i push Execute button:

s = 'hello'
print(s) 

Then can continue to test and get better autocompletion and color.

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As a alternative look at on of the best Python editor out there VS Code.
VS Code from start