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optparse: Callback example 1 is confusing #49077

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jkankiewicz mannequin opened this issue Jan 4, 2009 · 2 comments
Closed

optparse: Callback example 1 is confusing #49077

jkankiewicz mannequin opened this issue Jan 4, 2009 · 2 comments
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@birkenfeld
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@jkankiewicz
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jkankiewicz mannequin commented Jan 4, 2009

BPO 4827
Nosy @birkenfeld

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 = 'https://github.com/birkenfeld'
closed_at = <Date 2009-02-05.11:33:36.178>
created_at = <Date 2009-01-04.06:50:42.750>
labels = ['docs']
title = 'optparse: Callback example 1 is confusing'
updated_at = <Date 2009-02-05.11:33:36.177>
user = 'https://bugs.python.org/jkankiewicz'

bugs.python.org fields:

activity = <Date 2009-02-05.11:33:36.177>
actor = 'georg.brandl'
assignee = 'georg.brandl'
closed = True
closed_date = <Date 2009-02-05.11:33:36.178>
closer = 'georg.brandl'
components = ['Documentation']
creation = <Date 2009-01-04.06:50:42.750>
creator = 'jkankiewicz'
dependencies = []
files = []
hgrepos = []
issue_num = 4827
keywords = []
message_count = 2.0
messages = ['79039', '81206']
nosy_count = 2.0
nosy_names = ['georg.brandl', 'jkankiewicz']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue4827'
versions = ['Python 2.6', 'Python 2.5', 'Python 2.4', 'Python 3.0', 'Python 3.1', 'Python 2.7']
@jkankiewicz
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jkankiewicz mannequin commented Jan 4, 2009

"Callback example 1: trivial callback" reads

Here’s an example of a callback option that takes no arguments, and

simply records that the option was seen:

        def record_foo_seen(option, opt_str, value, parser):
            parser.saw_foo = True

        parser.add_option("--foo", action="callback",
callback=record_foo_seen)

but the following paragraph

Of course, you could do that with the store_true action.

is wrong because

        parser.add_option("--foo", action="store_true", dest="saw_foo")

would actually be duplicated by

        def record_foo_seen(option, opt_str, value, parser):
            parser.values.saw_foo = True

        parser.add_option("--foo", action="callback",
callback=record_foo_seen)
For example:
>>> from optparse import OptionParser
>>> parser = OptionParser()
>>> def record_foo_seen(option, opt_str, value, parser):
...     parser.saw_foo = True
...
>>> parser.add_option("--foo", action="callback", callback=record_foo_seen)
<Option at 0xab4f58: --foo>
>>> parser.parse_args(['--foo'])
(<Values at 0xabb0f8: {}>, [])
>>> parser = OptionParser()
>>> parser.add_option("--foo", action="store_true", dest="saw_foo")
<Option at 0xabb1e8: --foo>
>>> parser.parse_args(['--foo'])
(<Values at 0xabb1c0: {'saw_foo': True}>, [])
>>> parser = OptionParser()
>>> def record_foo_seen(option, opt_str, value, parser):
...     parser.values.saw_foo = True
...
>>> parser.add_option("--foo", action="callback", callback=record_foo_seen)
<Option at 0xabb508: --foo>
>>> parser.parse_args(['--foo'])
(<Values at 0xabb3f0: {'saw_foo': True}>, [])

@jkankiewicz jkankiewicz mannequin assigned birkenfeld Jan 4, 2009
@jkankiewicz jkankiewicz mannequin added the docs Documentation in the Doc dir label Jan 4, 2009
@birkenfeld
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You're right, I've fixed that in r69298.

@ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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