len(list(filter(lambda line: all([abs(x) >= 1 and abs(x) <= 3 for x in line]) and (all([x > 0 for x in line]) or all([x < 0 for x in line])), diffs))) Well, po

len(list(filter(lambda line: all([abs(x) >= 1 and abs(x) <= 3 for x in line]) and (all([x > 0 for x in line]) or all([x < 0 for x in line])), diffs))) Well, point taken about the ordering, but there are many more legible ways to have written that code. Not everything has to be a one liner. even: def f(diffs): cond = 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]) ) items = filter(cond, diffs) return len(list(items))