Convert, or unformat, a string to variables (like format(), but in reverse) in Python

Question

I have strings of the form Version 1.4.0\\n and Version 1.15.6\\n, and I\'d like a simple way of extracting the three numbers from them. I know I

Answer 1

Actually the Python regular expression library already provides the general functionality you are asking for. You just have to change the syntax of the pattern slightly

>>> import re
>>> from operator import itemgetter
>>> mystr='Version 1.15.6\n'
>>> m = re.match('Version (?P<_0>.+)\.(?P<_1>.+)\.(?P<_2>.+)', mystr)
>>> map(itemgetter(1), sorted(m.groupdict().items()))
['1', '15', '6']

As you can see, you have to change the (un)format strings from {0} to (?P<_0>.+). You could even require a decimal with (?P<_0>\d+). In addition, you have to escape some of the characters to prevent them from beeing interpreted as regex special characters. But this in turm can be automated again e.g. with

>>> re.sub(r'\\{(\d+)\\}', r'(?P<_\1>.+)', re.escape('Version {0}.{1}.{2}'))
'Version\\ (?P<_0>.+)\\.(?P<_1>.+)\\.(?P<_2>.+)'