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

No need to iterate over the version tuples. The built in comparison operator on lists and tuples already works exactly like you want it. You'll just need to zero extend the version lists to the corresponding length. With python 2.6 you can use izip_longest to pad the sequences.

from itertools import izip_longest
def version_cmp(v1, v2):
    parts1, parts2 = [map(int, v.split('.')) for v in [v1, v2]]
    parts1, parts2 = zip(*izip_longest(parts1, parts2, fillvalue=0))
    return cmp(parts1, parts2)

With lower versions, some map hackery is required.

def version_cmp(v1, v2):
    parts1, parts2 = [map(int, v.split('.')) for v in [v1, v2]]
    parts1, parts2 = zip(*map(lambda p1,p2: (p1 or 0, p2 or 0), parts1, parts2))
    return cmp(parts1, parts2)

Answer 2

This is a little more compact than your suggestion. Rather than filling the shorter version with zeros, I'm removing trailing zeros from the version lists after splitting.

def normalize_version(v):
    parts = [int(x) for x in v.split(".")]
    while parts[-1] == 0:
        parts.pop()
    return parts

def mycmp(v1, v2):
    return cmp(normalize_version(v1), normalize_version(v2))

Answer 3

In case you don't want to pull in an external dependency here is my attempt written for Python 3.x.

rc, rel (and possibly one could add c) are regarded as "release candidate" and divide the version number into two parts and if missing the value of the second part is high (999). Else letters produce a split and are dealt as sub-numbers via base-36 code.

import re
from itertools import chain
def compare_version(version1,version2):
    '''compares two version numbers
    >>> compare_version('1', '2') < 0
    True
    >>> compare_version('2', '1') > 0
    True
    >>> compare_version('1', '1') == 0
    True
    >>> compare_version('1.0', '1') == 0
    True
    >>> compare_version('1', '1.000') == 0
    True
    >>> compare_version('12.01', '12.1') == 0
    True
    >>> compare_version('13.0.1', '13.00.02') <0
    True
    >>> compare_version('1.1.1.1', '1.1.1.1') == 0
    True
    >>> compare_version('1.1.1.2', '1.1.1.1') >0
    True
    >>> compare_version('1.1.3', '1.1.3.000') == 0
    True
    >>> compare_version('3.1.1.0', '3.1.2.10') <0
    True
    >>> compare_version('1.1', '1.10') <0
    True
    >>> compare_version('1.1.2','1.1.2') == 0
    True
    >>> compare_version('1.1.2','1.1.1') > 0
    True
    >>> compare_version('1.2','1.1.1') > 0
    True
    >>> compare_version('1.1.1-rc2','1.1.1-rc1') > 0
    True
    >>> compare_version('1.1.1a-rc2','1.1.1a-rc1') > 0
    True
    >>> compare_version('1.1.10-rc1','1.1.1a-rc2') > 0
    True
    >>> compare_version('1.1.1a-rc2','1.1.2-rc1') < 0
    True
    >>> compare_version('1.11','1.10.9') > 0
    True
    >>> compare_version('1.4','1.4-rc1') > 0
    True
    >>> compare_version('1.4c3','1.3') > 0
    True
    >>> compare_version('2.8.7rel.2','2.8.7rel.1') > 0
    True
    >>> compare_version('2.8.7.1rel.2','2.8.7rel.1') > 0
    True

    '''
    chn = lambda x:chain.from_iterable(x)
    def split_chrs(strings,chars):
        for ch in chars:
            strings = chn( [e.split(ch) for e in strings] )
        return strings
    split_digit_char=lambda x:[s for s in re.split(r'([a-zA-Z]+)',x) if len(s)>0]
    splt = lambda x:[split_digit_char(y) for y in split_chrs([x],'.-_')]
    def pad(c1,c2,f='0'):
        while len(c1) > len(c2): c2+=[f]
        while len(c2) > len(c1): c1+=[f]
    def base_code(ints,base):
        res=0
        for i in ints:
            res=base*res+i
        return res
    ABS = lambda lst: [abs(x) for x in lst]
    def cmp(v1,v2):
        c1 = splt(v1)
        c2 = splt(v2)
        pad(c1,c2,['0'])
        for i in range(len(c1)): pad(c1[i],c2[i])
        cc1 = [int(c,36) for c in chn(c1)]
        cc2 = [int(c,36) for c in chn(c2)]
        maxint = max(ABS(cc1+cc2))+1
        return base_code(cc1,maxint) - base_code(cc2,maxint)
    v_main_1, v_sub_1 = version1,'999'
    v_main_2, v_sub_2 = version2,'999'
    try:
        v_main_1, v_sub_1 = tuple(re.split('rel|rc',version1))
    except:
        pass
    try:
        v_main_2, v_sub_2 = tuple(re.split('rel|rc',version2))
    except:
        pass
    cmp_res=[cmp(v_main_1,v_main_2),cmp(v_sub_1,v_sub_2)]
    res = base_code(cmp_res,max(ABS(cmp_res))+1)
    return res


import random
from functools import cmp_to_key
random.shuffle(versions)
versions.sort(key=cmp_to_key(compare_version))

Answer 4

I did this in order to be able to parse and compare the Debian package version string. Please notice that it is not strict with the character validation.

This might be helpful as well:

#!/usr/bin/env python

# Read <https://www.debian.org/doc/debian-policy/ch-controlfields.html#s-f-Version> for further informations.

class CommonVersion(object):
    def __init__(self, version_string):
        self.version_string = version_string
        self.tags = []
        self.parse()

    def parse(self):
        parts = self.version_string.split('~')
        self.version_string = parts[0]
        if len(parts) > 1:
            self.tags = parts[1:]


    def __lt__(self, other):
        if self.version_string < other.version_string:
            return True
        for index, tag in enumerate(self.tags):
            if index not in other.tags:
                return True
            if self.tags[index] < other.tags[index]:
                return True

    @staticmethod
    def create(version_string):
        return UpstreamVersion(version_string)

class UpstreamVersion(CommonVersion):
    pass

class DebianMaintainerVersion(CommonVersion):
    pass

class CompoundDebianVersion(object):
    def __init__(self, epoch, upstream_version, debian_version):
        self.epoch = epoch
        self.upstream_version = UpstreamVersion.create(upstream_version)
        self.debian_version = DebianMaintainerVersion.create(debian_version)

    @staticmethod
    def create(version_string):
        version_string = version_string.strip()
        epoch = 0
        upstream_version = None
        debian_version = '0'

        epoch_check = version_string.split(':')
        if epoch_check[0].isdigit():
            epoch = int(epoch_check[0])
            version_string = ':'.join(epoch_check[1:])
        debian_version_check = version_string.split('-')
        if len(debian_version_check) > 1:
            debian_version = debian_version_check[-1]
            version_string = '-'.join(debian_version_check[0:-1])

        upstream_version = version_string

        return CompoundDebianVersion(epoch, upstream_version, debian_version)

    def __repr__(self):
        return '{} {}'.format(self.__class__.__name__, vars(self))

    def __lt__(self, other):
        if self.epoch < other.epoch:
            return True
        if self.upstream_version < other.upstream_version:
            return True
        if self.debian_version < other.debian_version:
            return True
        return False


if __name__ == '__main__':
    def lt(a, b):
        assert(CompoundDebianVersion.create(a) < CompoundDebianVersion.create(b))

    # test epoch
    lt('1:44.5.6', '2:44.5.6')
    lt('1:44.5.6', '1:44.5.7')
    lt('1:44.5.6', '1:44.5.7')
    lt('1:44.5.6', '2:44.5.6')
    lt('  44.5.6', '1:44.5.6')

    # test upstream version (plus tags)
    lt('1.2.3~rc7',          '1.2.3')
    lt('1.2.3~rc1',          '1.2.3~rc2')
    lt('1.2.3~rc1~nightly1', '1.2.3~rc1')
    lt('1.2.3~rc1~nightly2', '1.2.3~rc1')
    lt('1.2.3~rc1~nightly1', '1.2.3~rc1~nightly2')
    lt('1.2.3~rc1~nightly1', '1.2.3~rc2~nightly1')

    # test debian maintainer version
    lt('44.5.6-lts1', '44.5.6-lts12')
    lt('44.5.6-lts1', '44.5.7-lts1')
    lt('44.5.6-lts1', '44.5.7-lts2')
    lt('44.5.6-lts1', '44.5.6-lts2')
    lt('44.5.6-lts1', '44.5.6-lts2')
    lt('44.5.6',      '44.5.6-lts1')

Answer 5

How about using Python's distutils.version.StrictVersion?

>>> from distutils.version import StrictVersion
>>> StrictVersion('10.4.10') > StrictVersion('10.4.9')
True

So for your cmp function:

>>> cmp = lambda x, y: StrictVersion(x).__cmp__(y)
>>> cmp("10.4.10", "10.4.11")
-1

If you want to compare version numbers that are more complex distutils.version.LooseVersion will be more useful, however be sure to only compare the same types.

>>> from distutils.version import LooseVersion, StrictVersion
>>> LooseVersion('1.4c3') > LooseVersion('1.3')
True
>>> LooseVersion('1.4c3') > StrictVersion('1.3')  # different types
False

LooseVersion isn't the most intelligent tool, and can easily be tricked:

>>> LooseVersion('1.4') > LooseVersion('1.4-rc1')
False

To have success with this breed, you'll need to step outside the standard library and use setuptools's parsing utility parse_version.

>>> from pkg_resources import parse_version
>>> parse_version('1.4') > parse_version('1.4-rc2')
True

So depending on your specific use-case, you'll need to decide whether the builtin distutils tools are enough, or if it's warranted to add as a dependency setuptools.