New submission from Steven Bethard <[email protected]>:
What steps will reproduce the problem?
parser = argparse.ArgumentParser()
parser.add_argument('--foo', nargs=2, metavar=('X','Y','Z'))
parser.parse_args(['-h'])
The error dosn't show up until help is formatted.
Giving any incorrect length of metavar will produce the problem, which
includes a tuple whos length doesn't match a numerical value, more than two
metavars to '*' or '+', and more than one metavar to '?'. Furthermore, a tuple
of length one causes the error when nargs is greater than 1, '*', or '+'.
What is the expected output? What do you see instead?
When the help is displayed, you get:
TypeError: not all arguments converted during string formatting
Or a similar error message for other cases.
It would be expected that the error message would be more specific. The
error should definitely be raised when add_argument is called, rather than
later.
There should be a test that does something like:
for meta in ('X', ('X',), ('X','Y'), ('X','Y','Z')):
for n in (1, 2, 3, '?', '+', '*'):
parser = argparse.ArgumentParser()
parser.add_argument('--foo', nargs=n, metavar=meta)
parser.format_help()
and makes sure that the error shows up in add_argument, not format_help.
----------
components: Library (Lib)
messages: 111317
nosy: bethard
priority: normal
severity: normal
stage: needs patch
status: open
title: Calling argparse's add_argument with the wrong number of metavars causes
delayed error message
type: behavior
versions: Python 2.7, Python 3.2
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Python tracker <[email protected]>
<http://bugs.python.org/issue9348>
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