On 20/02/24 05:58, Grant Edwards via Python-list wrote:
Here's a demonstration of how to hook custom code into the f-string
formatting engine. It's brilliantly depraved.

https://stackoverflow.com/questions/55876683/hook-into-the-builtin-python-f-string-format-machinery

 From the above:

     You can, but only if you write evil code that probably should
     never end up in production software. So let's get started!
I'm not going to integrate it into your library, but I will show
     you how to hook into the behavior of f-strings. This is roughly
     how it'll work:
1. Write a function that manipulates the bytecode instructions of
         code objects to replace FORMAT_VALUE instructions with calls
         to a hook function;
2. Customize the import mechanism to make sure that the bytecode
         of every module and package (except standard library modules
         and site-packages) is modified with that function.

Final code is here:

https://github.com/mivdnber/formathack

Some of this (Expression components inside f-strings) newly available in v3.12 (PEP-701) - which can be used in production...

--
Regards,
=dn
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