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

打开 issue 中链接的 Python Setup and Usage > Using Python on Windows > Troubleshooting 页面，并检查现有的症状表。将关于 PATH 和重启终端的拟议指南与链接的 PR gh-143964 和 gh-143981 进行比较；当约定的指南出现在 Troubleshooting 页面中时，文档工作即完成。