How to use find to remove *.py~ and *.pyc files at once?

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http://unix.stackexchange.com – I want to cleanup a directory (and subdirectories) from each occurrance of the .py and .pyc files. I tried the following find . -name '*pyc' -o -name '*py~' -exec rm -f {} \; which left out all pyc files. When doing find . -name '*pyc' -o -name '*py~' the command finds the pyc files, which are not deleted, whatsoever. Any insights? (HowTos)