abs(x) >= 1 and abs(x) <= 3 Is also unidiomatic in Python. 1 <= abs(x) <= 3 Means the same thing and tightens it up a bit, and reads better since it's indi

abs(x) >= 1 and abs(x) <= 3 Is also unidiomatic in Python. 1 <= abs(x) <= 3 Means the same thing and tightens it up a bit, and reads better since it's indicating that you're testing if something is in a range more clearly. EDIT: To add: The filter, list construction, and len aren't needed either. It's just: sum(map(predicate, diffs)) # this counts the number of elements in diffs which satisfy predicate, map is lazy so no big memory overhead Or alternatively: sum(predicate(diff) for diff in diffs) The predicate is complex enough and used twice, so it warrants extraction to its own named function (or lambda assigned to a variable), but even if it were still embedded this form would be slightly clearer (along with adding the line breaks and removing the extra list generations): sum(map(lambda line: all(1 <= abs(x) <= 3 for x in line) and (all(x > 0 for x in line) or all(x < 0 for x in line)), diffs))