How to split a sequence according to a predicate?

Question

I very often run into the need to split a sequence into the two subsequences of elements that satisfy and don\'t satisfy a given predicate (preserving the original relative

Answer 1

I know you said you didn't want to write your own function, but I can't imagine why. Your solutions involve writing your own code, you just aren't modularizing them into functions.

This does exactly what you want, is understandable, and only evaluates the predicate once per element:

def splitter(data, pred):
    yes, no = [], []
    for d in data:
        if pred(d):
            yes.append(d)
        else:
            no.append(d)
    return [yes, no]

If you want it to be more compact (for some reason):

def splitter(data, pred):
    yes, no = [], []
    for d in data:
        (yes if pred(d) else no).append(d)
    return [yes, no]