Running Sage as a Command and Importing as a Python Library in Kali Linux

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I've successfully managed to install SageMath on Kali Linux by following this guide : pastebin.com/6m6ypB2N. While I can run SageMath using the following command: ./sage However, this is different from other people's Sage, where they can run it using the sage command like Python. Also, I want to import Sage as a library in Python using: from sage.all import * since many prewritten algorithms and libraries are written in Python. I have no idea why my Sage installation behaves differently and not like other people's installations, and I can't find any related guides anywhere.