Who cares if the program takes ten seconds to run instead of one when it only needs to run once and coding it in Python takes a few hours instead of a day or two in C?
If you need performance that badly, by all means, use C. If you have ten ideas for simple programs and just want to code them real quick without fighting the compiler and worrying about all the little shit that C demands from you, then there's nothing wrong with using Python.
Everything in life is a tradeoff. Use the right tool for the job.