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  • Vlad Bezden thinks this is interesting:

number_of_vowels = len(filter(lambda letter: letter in 'aeiou', s))

From

Cover of Serious Python

Note

This line doesn't work because a filter is a generator and len function can't be applied to the generator. Instead, list comprehension can be used:

number_of_vowels = len([letter for letter in s if letter in "aeiou"])