New submission from John W. Shipman <j...@nmt.edu>:
optparse's .parse_args() method has a 'values=...' keyword argument
that is documented as:
'object to store option arguments in (default: a new instance of
optparse.Values)'
There is no description of what types this argument may have.
I was writing a class to digest the command line, and my bright
idea was to request that .parse_args deposit the attribute
values right into 'self' in the class constructor.
This works only for arguments that were actually specified; it
stores no attribute value at all for missing options that have
associated default options.
Below is a small script that demonstrates this behavior. It
accepts one '-t' option, with default value 'DEFAULT'. Here
is the output when the option is specified, and when it is not:
$ bad -t foo
foo
$ bad
Traceback (most recent call last):
File "bad", line 23, in <module>
main()
File "bad", line 13, in main
print args.test
AttributeError: Args instance has no attribute 'test'
Here is the test script:
#!/usr/bin/env python
#================================================================
# bad: Demonstrate defect in optparse.
# I want optparse to honor the .parse_args(values=...)
# argument to store the attributes directly in self in the
# constructor. It works only for options actually specified;
# default values are not copied into self.
#----------------------------------------------------------------
import sys, optparse
def main():
args = Args()
print args.test
class Args:
def __init__(self):
parser = optparse.OptionParser()
parser.add_option ( "-t", "--test", dest="test",
type="string", default="DEFAULT" )
discard, positionals = parser.parse_args(values=self)
if __name__ == "__main__":
main()
--------------------------------------------------------------
----------
components: Library (Lib)
messages: 105875
nosy: j...@nmt.edu
priority: normal
severity: normal
status: open
title: optparse: parse_args(values=...) does not set up default values
type: behavior
versions: Python 2.6
_______________________________________
Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue8735>
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