Version number comparison in Python
Remove the uninteresting part of the string (trailing zeroes and dots), and then compare the lists of numbers.
import re
def mycmp(version1, version2):
def normalize(v):
return [int(x) for x in re.sub(r'(\.0+)*$','', v).split(".")]
return cmp(normalize(version1), normalize(version2))
This is the same approach as Pär Wieslander, but a bit more compact:
Here are some tests, thanks to "How to compare two strings in dot separated version format in Bash?":
assert mycmp("1", "1") == 0
assert mycmp("2.1", "2.2") < 0
assert mycmp("3.0.4.10", "3.0.4.2") > 0
assert mycmp("4.08", "4.08.01") < 0
assert mycmp("3.2.1.9.8144", "3.2") > 0
assert mycmp("3.2", "3.2.1.9.8144") < 0
assert mycmp("1.2", "2.1") < 0
assert mycmp("2.1", "1.2") > 0
assert mycmp("5.6.7", "5.6.7") == 0
assert mycmp("1.01.1", "1.1.1") == 0
assert mycmp("1.1.1", "1.01.1") == 0
assert mycmp("1", "1.0") == 0
assert mycmp("1.0", "1") == 0
assert mycmp("1.0", "1.0.1") < 0
assert mycmp("1.0.1", "1.0") > 0
assert mycmp("1.0.2.0", "1.0.2") == 0
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
.