There is no such thing as a "function declaration" in Python. The keyword is "def", which is the first three letters of the word "define" (and not a prefix of "declare"), for a reason.

The entire point of it being an executable statement is to let you change things on the fly. This is key to how the REPL works. If I have `def foo(): ...` twice, the second one overwrites the first. There's no need to do any checks ahead of time, and it works the same way in the REPL as in a source file, without any special logic, for the exact same reason that `foo = 1` works when done twice. It's actually very elegant.

People who don't like these decisions have plenty of other options for languages they can use. Only Python is Python. Python should not become not-Python in order to satisfy people who don't like Python and don't understand what Python is trying to be.