How can we get a character which appears most frequently in a string? There’s a quiz to write a function for the purpose on CheckIO.

Probably, it’s not difficult to write a function for it naively. However, if you need to write a one line function for it, the difficulty goes up radically. I found a solution by shiracamus, which is one line. Amazing!

#!/usr/bin/env python3

checkio = lambda t: max('abcdefghijklmnopqrstuvwxyz', key = t.lower().count)

if __name__ == '__main__':
	assert checkio("Hello World!") == "l", "Hello test"
	assert checkio("How do you do?") == "o", "O is most wanted"
	assert checkio("One") == "e", "All letter only once."
	assert checkio("Oops!") == "o", "Don't forget about lower case."
	assert checkio("AAaooo!!!!") == "a", "Only letters."
	assert checkio("abe") == "a", "The First."
	assert checkio("a" * 9000 + "b" * 1000) == "a", "Long."

This idea is awesome! max function can take key=func arg to specify which function to use for calculating max. count for string behaves as follows:

>>> "We are what we repeatedly do".count("a")

So, checkio function works as intended.