Well these are two completely different languages. Python is a scripting and interpreted language while C# is a programming and compiled language. C# generally only runs on Windows while for Python all the computer needs is an interpreter for its OS.
I am a Java developer mainly, and I love C# because it's so similar and has a bunch of things I think Java should have (operation overloads, class extensions, and many more).
I generally only use Python for quick maintenance scripts, but I once used it to make an artificial neural network which is obviously a much bigger project.
It all comes down to preference. I'm assuming that this will be your first language from what you've said in the OP, so I would recommend Python out of those two. Don't become a Pydick and only write Python. Once you've got a handle on it learn some other, more advanced languages.