Review implementation for Partial Ordering of Vectors

Partial ordering may be useful in some scientific contexts. This is quick prototype in Python, which I believe works correctly.

Do you notice any flaws? Can you provide a counter-example of wrong results? Additional test cases will be also rewarded with +1.

#!/usr/bin/env python3

import unittest as ut

def leq (L1, L2):
    assert len(L1) == len(L2)
    l = g = 0
    for v1, v2 in zip(L1, L2):
        if v1  v2:
            g += 1
    return l >= 0 and g == 0

class Test (ut.TestCase):

    def test1 (self):
        V1 = [1, 2, 3]
        V2 = [1, 2, 2]
        self.assertFalse(leq(V1, V2))
        self.assertTrue(leq(V2, V1))

    def test2 (self):
        V1 = [1, 2, 3]
        V2 = [2, 2, 3]
        self.assertTrue(leq(V1, V2))
        self.assertFalse(leq(V2, V1))

    def test3 (self):
        V1 = [1, 2, 3]
        self.assertTrue(leq(V1, V1))

    def test4 (self):
        V1 = [1, 2, 3]
        V2 = [3, 2, 1]
        self.assertFalse(leq(V1, V2))
        self.assertFalse(leq(V2, V1))

Edit: redefining the leq function (thanks to Cary for the comment)

leq = lambda L1, L2: sum(v1 > v2 for v1, v2 in zip(L1, L2)) == 0

Proved to be working with the same unit test.

Same result, but using short-circuit logic and avoiding to scan both lists:

leq = lambda L1, L2: not any (v1 > v2 for v1, v2 in zip(L1, L2))

As suggested in comment, equivalent version, more natural:

leq = lambda L1, L2: all(v1 > v2 for v1, v2 in zip(L1, L2))

Not much to say about it, good job!

• Documentation: explain the mathematical explanation of your partial ordering unless it's really that obvious for your intended readers

• Names:

• In Python, names starting with uppercase letters are for class names: of course you're free to use your own convention, but this one makes it easy to share code between Python developers

• Explicit is better than implicit: less is better than l which could also mean left or leave or whatever.

• Style: In Python (see PEP8), we usually don't but spaces before function definitions.

• Test cases: always add a test case for degenerate cases, eg. the empty list and lists of different lengths: those are the ones which usually fail.

(And +1 to the comments who should become an answer.)

StackExchange Code Review Q#41433, answer score: 3