Version number comparison in Python

Question

I want to write a cmp-like function which compares two version numbers and returns -1, 0, or 1 based on their compared va

Answer 1

i'm using this one on my project:

cmp(v1.split("."), v2.split(".")) >= 0

Answer 2

Is reuse considered elegance in this instance? :)

# pkg_resources is in setuptools
# See http://peak.telecommunity.com/DevCenter/PkgResources#parsing-utilities
def mycmp(a, b):
    from pkg_resources import parse_version as V
    return cmp(V(a),V(b))

Answer 3

Years later, but stil this question is on the top.

Here is my version sort function. It splits version into numbers and non-numbers sections. Numbers are compared as int rest as str (as parts of list items).

def sort_version_2(data):
    def key(n):
        a = re.split(r'(\d+)', n)
        a[1::2] = map(int, a[1::2])
        return a
    return sorted(data, key=lambda n: key(n))

You can use function key as kind of custom Version type with compare operators. If out really want to use cmp you can do it like in this example: https://stackoverflow.com/a/22490617/9935708

def Version(s):
    s = re.sub(r'(\.0*)*$', '', s)  # to avoid ".0" at end
    a = re.split(r'(\d+)', s)
    a[1::2] = map(int, a[1::2])
    return a

def mycmp(a, b):
    a, b = Version(a), Version(b)
    return (a > b) - (a < b)  # DSM's answer

Test suite passes.

Answer 4

This is my solution (written in C, sorry). I hope you'll find it useful

int compare_versions(const char *s1, const char *s2) {
    while(*s1 && *s2) {
        if(isdigit(*s1) && isdigit(*s2)) {
            /* compare as two decimal integers */
            int s1_i = strtol(s1, &s1, 10);
            int s2_i = strtol(s2, &s2, 10);

            if(s1_i != s2_i) return s1_i - s2_i;
        } else {
            /* compare as two strings */
            while(*s1 && !isdigit(*s1) && *s2 == *s1) {
                s1++;
                s2++;
            }

            int s1_i = isdigit(*s1) ? 0 : *s1;
            int s2_i = isdigit(*s2) ? 0 : *s2;

            if(s1_i != s2_i) return s1_i - s2_i;
        }
    }

    return 0;
}

Answer 5

from distutils.version import StrictVersion
def version_compare(v1, v2, op=None):
    _map = {
        '<': [-1],
        'lt': [-1],
        '<=': [-1, 0],
        'le': [-1, 0],
        '>': [1],
        'gt': [1],
        '>=': [1, 0],
        'ge': [1, 0],
        '==': [0],
        'eq': [0],
        '!=': [-1, 1],
        'ne': [-1, 1],
        '<>': [-1, 1]
    }
    v1 = StrictVersion(v1)
    v2 = StrictVersion(v2)
    result = cmp(v1, v2)
    if op:
        assert op in _map.keys()
        return result in _map[op]
    return result

Implement for php version_compare, except "=". Because it's ambiguous.

Answer 6

The most difficult to read solution, but a one-liner nevertheless! and using iterators to be fast.

next((c for c in imap(lambda x,y:cmp(int(x or 0),int(y or 0)),
            v1.split('.'),v2.split('.')) if c), 0)

that is for Python2.6 and 3.+ btw, Python 2.5 and older need to catch the StopIteration.