String comparison technique used by Python

Question

I\'m wondering how Python does string comparison, more specifically how it determines the outcome when a less than (<) or greater than (>) op

Answer 1

A pure Python equivalent for string comparisons would be:

def less(string1, string2):
    # Compare character by character
    for idx in range(min(len(string1), len(string2))):
        # Get the "value" of the character
        ordinal1, ordinal2 = ord(string1[idx]), ord(string2[idx])
        # If the "value" is identical check the next characters
        if ordinal1 == ordinal2:
            continue
        # It's not equal so we're finished at this index and can evaluate which is smaller.
        else:
            return ordinal1 < ordinal2
    # We're out of characters and all were equal, so the result depends on the length
    # of the strings.
    return len(string1) < len(string2)

This function does the equivalent of the real method (Python 3.6 and Python 2.7) just a lot slower. Also note that the implementation isn't exactly "pythonic" and only works for < comparisons. It's just to illustrate how it works. I haven't checked if it works like Pythons comparison for combined unicode characters.

A more general variant would be:

from operator import lt, gt

def compare(string1, string2, less=True):
    op = lt if less else gt
    for char1, char2 in zip(string1, string2):
        ordinal1, ordinal2 = ord(char1), ord(char1)
        if ordinal1 == ordinal2:
            continue
        else:
            return op(ordinal1, ordinal2)
    return op(len(string1), len(string2))