[BoppreH]

Some years ago I wrote a Python function, "replace_me"[1], that edits the caller's source code. You can use it for code generation, inserting comments, generating fixed random seeds, etc.

And one more use case I found was exactly what TFA describes, but even easier:

   import replace_me
   replace_me.test(1+1)

Once executed, it evaluates the argument and becomes an assertion:

   import replace_me
   replace_me.test(1+1, 2)

I never actually used it for anything important, but it comes back to my mind once in a while.

[1]: https://github.com/boppreh/replace_me