Default return value in ConfigParser

[jjdominguezm]

BPO	6751
Nosy	@amauryfa, @merwok, @ambv
Superseder	bpo-9421: configparser.ConfigParser's getint, getboolean and getfloat don't accept vars
Files	configparser.py.diff test_cfgparser.py.diff

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2010-08-09.21:10:00.237>
created_at = <Date 2009-08-21.08:57:56.221>
labels = ['type-feature', 'library']
title = 'Default return value in ConfigParser'
updated_at = <Date 2010-08-09.21:10:00.236>
user = 'https://bugs.python.org/jjdominguezm'

bugs.python.org fields:

activity = <Date 2010-08-09.21:10:00.236>
actor = 'lukasz.langa'
assignee = 'none'
closed = True
closed_date = <Date 2010-08-09.21:10:00.237>
closer = 'lukasz.langa'
components = ['Library (Lib)']
creation = <Date 2009-08-21.08:57:56.221>
creator = 'jjdominguezm'
dependencies = []
files = ['18122', '18123']
hgrepos = []
issue_num = 6751
keywords = ['patch']
message_count = 7.0
messages = ['91808', '109862', '111067', '111166', '112572', '113159', '113473']
nosy_count = 5.0
nosy_names = ['amaury.forgeotdarc', 'eric.araujo', 'jjdominguezm', 'BreamoreBoy', 'lukasz.langa']
pr_nums = []
priority = 'normal'
resolution = 'duplicate'
stage = 'patch review'
status = 'closed'
superseder = '9421'
type = 'enhancement'
url = 'https://bugs.python.org/issue6751'
versions = ['Python 3.2']

[jjdominguezm]

I think it is useful, at least for me, to add an argument, default, to
[Safe,Raw]ConfigParser.get that, if present, will be returned if the
methid fails to return the value.

That is, instead of rasing an exception, return default, if present.

It could be done overriding the get method in SafeConfigParser,
something like this:

class SafeConfigParser(ConfigParser):
    def get(self, section, option, raw=False, vars=None, **kwds):
        try:
            return super().get(section, option, raw, vars)
        except Exception as exc:
            if "default" in kwds:
                return kwds["default"]
            raise exc

[BreamoreBoy]

A short inline patch is proposed, would something like this be acceptable?

[amauryfa]

The idea is fine (dict.get also has a 'default' parameter) but this patch is very incomplete:

• the enhancement should be applied to the three Parsers
• it needs unit tests.

[jjdominguezm]

I've applied the enhancement to the three parsers, actually I've made the change to RawconfigParser with a small change to ConfigParser.

I've also created some unit tests.

[merwok]

Why is it needed to add varargs and kwargs instead of only a new “default” argument?

[jjdominguezm]

I would like the method to have the exact same behavior as before if the "default" argument is not present, and return the given default value when "deafult" argument is present.

If you simply add a "default" keyword, it will always be present and you wouldn't know if the user wants the exception thrown or the default value returned.

Do you know how to program this using a "default" keyword argument?

[ambv]

This issue is superseded by bpo-9421.