[New-bugs-announce] [issue14991] Option for regex groupdict() to show only matching names

[Raymond Hettinger]

New submission from Raymond Hettinger <raymond.hettinger at gmail.com>:

Currently, mo.groupdict() always inserts a default value for unmatched named groups.   This is helpful in some use cases and awkward in others.

I propose adding an option to suppress default entries:

>>> # CURRENT WAY
>>> pattern = r'(?P<TITLE>Mrs |Mr |Dr )?(?P<LASTNAME>\w+)(?P<SUFFIX> Phd| JD)?'
>>> print re.match(pattern, 'Dr Who').groupdict()
{'LASTNAME': 'Who', 'SUFFIX': None, 'TITLE': 'Dr '}

>>> # PROPOSED WAY
>>> print re.match(pattern, 'Dr Who').groupdict(nodefault=True)
{'LASTNAME': 'Who', 'TITLE': 'Dr '}

>>> # UPSTREAM VARIANT
>>> print re.match(pattern, 'Dr Who', re.NODEFAULT).groupdict()
{'LASTNAME': 'Who', 'TITLE': 'Dr '}

There is probably a better name than "nodefault", but I would like to see someway to improve the usability of groupdict().

----------
messages: 162223
nosy: rhettinger
priority: normal
severity: normal
status: open
title: Option for regex groupdict() to show only matching names
type: enhancement
versions: Python 3.4

_______________________________________
Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue14991>
_______________________________________