One more possible solution at Troubleshooting page

Symptom	Things to try
python gives me a “command not found” error or opens the Store app when I type it in my terminal.	...
py gives me a “command not found” error or opens the Store app when I type it in my terminal.	...
...	...
pip gives me a “command not found” error or opens the Store app when I type it in my terminal.	...

— at Python Setup and Usage > 4. Using Python on Windows > Troubleshooting

Here's one more possible reason for the symptoms above: the terminal just doesn't get PATH Variable updated (if PATH is modified when the terminal is still running).
And the respective solution is simple: Check PATH and reopen the terminal, then try again.

Linked PRs

• gh-143964
• gh-143981

開啟 issue 中連結的 Python Setup and Usage > Using Python on Windows > Troubleshooting 頁面，並檢視現有的症狀表。將關於 PATH 和重新啟動終端機的擬議指南與連結的 PR gh-143964 和 gh-143981 進行比較；當約定的指南出現在 Troubleshooting 頁面中時，文件工作即完成。