zsh-style subpattern matching for fnmatch/glob

[efd54b2f-2106-478f-aa8c-13cab7280b31]

BPO	4573
Nosy	@birkenfeld, @rhettinger, @terryjreedy, @giampaolo, @tjguk
Files	zsh-fnmatch.diff zsh-fnmatch-2.7.diff: Backport of original patch for 2.7

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GitHub fields: ```python assignee = None closed_at = None created_at = labels = ['type-feature', 'library', '3.10'] title = 'zsh-style subpattern matching for fnmatch/glob' updated_at = user = 'https://bugs.python.org/erickt' ``` bugs.python.org fields: ```python activity = actor = 'terry.reedy' assignee = 'none' closed = False closed_date = None closer = None components = ['Library (Lib)'] creation = creator = 'erickt' dependencies = [] files = ['12259', '12273'] hgrepos = [] issue_num = 4573 keywords = ['patch'] message_count = 7.0 messages = ['77216', '77278', '85073', '85130', '85131', '85180', '379369'] nosy_count = 8.0 nosy_names = ['georg.brandl', 'rhettinger', 'terry.reedy', 'ironfroggy', 'giampaolo.rodola', 'tim.golden', 'erickt', 'kveretennicov'] pr_nums = [] priority = 'normal' resolution = None stage = None status = 'open' superseder = None type = 'enhancement' url = 'https://bugs.python.org/issue4573' versions = ['Python 3.10'] ```

[efd54b2f-2106-478f-aa8c-13cab7280b31]

As I mentioned on python-ideas, I my project needs to extend fnmatch to support zsh-style globbing, where you can use brackets to designate subexpressions. Say you had a directory structure like this:

foo/ foo.ext1 foo.ext2 bar/ foo.ext1 foo.ext2

The subexpressions will let you do patterns like this:

>>> glob.glob('foo/foo.{ext1,ext2}')
['foo/foo.ext1', 'foo/foo.ext2']
>>> glob.glob('foo/foo.ext{1,2}')
['foo/foo.ext1', 'foo/foo.ext2']
>>> glob.glob('{foo,bar}')
['bar', 'foo']
>>> glob.glob('{foo,bar}/foo*')
['bar/foo.ext1', 'bar/foo.ext2', 'foo/foo.ext1', 'foo/foo.ext2']
>>> glob.glob('{foo,bar}/foo.{ext*}')
['bar/foo.ext1', 'bar/foo.ext2', 'foo/foo.ext1', 'foo/foo.ext2']
>>> glob.glob('{f?o,b?r}/foo.{ext*}')
['bar/foo.ext1', 'bar/foo.ext2', 'foo/foo.ext1', 'foo/foo.ext2']

Would this be interesting to anyone else? It would unfortunately break fnmatch since it currently treats {} as ordinary characters. It'd be easy to work around that by adding a flag or using a different function name though. Anyway, here's the patch against the head of py3k.

[2a6cddb0-fa4b-409a-88ae-31164262b1d8]

This should be applicable to 2.7, at least, as well. Here is a backport of the patch against trunk.

[birkenfeld]

This can't go in like this, since suddenly accepting braces is a subtle change of semantics. I could imagine adding another function though, that has extended zsh-like globbing abilities.

[efd54b2f-2106-478f-aa8c-13cab7280b31]

I completely agree, Georg. I tried to get this in before 3.0, but it didn't work out which is a shame. I assume you also feel that we couldn't make a backwards compatible change in 3.1, right? I thought I heard that 3.1 may break some things in 3.0, but I'm not positive.

Got any suggestions for a function name? Here are some I have in mind, but none of them are particularly good:

fnmatch.fnmatch2 fnmatch.efnmatch fnmatch.extended_fnmatch

glob.glob2 glob.eglob glob.extended_glob

[rhettinger]

I like glob_ext() and fnmatch_ext().

[tjguk]

Is there mileage for glob.glob to grow a dialect param, with a default value to keep it backwards compatible? Otherwise, presumably, proponents of some other xsh variant will come forward with their scheme of matching, and regex-followers with theirs and so on.

[terryjreedy]

Raymond, is this zsh addition still relevant or out of date?