How would I implement copy protection?

[GalaxyCoyote]

I need a way to tell if my .py file has been copied (but if you have any other copy protection techniques then please comment).

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I am coding a software that can perform basic tasks like reading and writing to file etc.

I need some help implementing a copy protection feature, if there is any copy protection that I could use please let me know! (The general idea is to stop people my friends spamming my software to their friends, I only want me and a select group of friends to use this software thanks in advance!)

[ThomasL]

If you find a solution you will become rich, because there is no such copy protection.
I´m that old to know copy protected floppy discs that had hardware magnetic faults
to prevent copying. Didn´t prevent anything.
The latest copy protection that i know was DENUVO.
It was used to protect games to get cracked and copied.
Didn´t work that well either, it just delayed the process.