From the Python style guide (PEP 8), on comments: Python coders from non-English speaking countries: please write your comments in English, unless you are 120%

From the Python style guide (PEP 8), on comments: Python coders from non-English speaking countries: please write your comments in English, unless you are 120% sure that the code will never be read by people who don't speak your language. And that's for all code written in Python, not just the code that goes into Python. Guido is Dutch.