On 20 November 2012 10:02, Johannes Bauer dfnsonfsdu...@gmx.de wrote:
Hi list,
I have a problem with Python3.2's argparse module. The following sample:
parser = argparse.ArgumentParser(prog = sys.argv[0])
parser.add_argument(-enc, metavar = enc, nargs = +, type = str,
default = [ utf-8 ])
parser.add_argument(pattern, metavar = pattern, type = str, nargs = 1)
parser.add_argument(filename, metavar = filename, type = str, nargs =
1)
args = parser.parse_args(sys.argv[1:])
illustrates the problem: I want to be able to specify an encoding one or
more times (multiple encodings possible), have a pattern and a filename
as the last two arguments.
This works as long as I don't specify '-enc' on the command line. If I
do, for example
./foo -enc myencoding mypattern myfile
The -enc greedy parser seems to capture [myencoding, mypattern,
myfile], leaving nothing for pattern and filename, yielding an error:
./foo: error: too few arguments
How can I force positional arguments to take precedence over optional
arguments? I could exclude them from the parsing altogether, but that
would make them not appear in the help page (which I'd like to avoid).
My first suggestion would be to change -enc to --enc,
my second to make the input --enc FIRST --enc SECOND --enc THIRD...
pattern filename (action=append, remove nargs=+),
and my third to use docopt (docopt.org) where the example you have posted
is just:
-
My Program.
Usage:
my_prog.py [--enc=encoding...] pattern filename
Options:
--enc encoding [default: UTF-8]
from docopt import docopt
arguments = docopt(__doc__)
--*
Note that this will not work if you don't take my first two suggestions.
An alternative is like mplayer's, where it accepts comma-delimited lists:
my_prog.py --enc UTF-8,ASCII,FOO,BAR pattern% filename.txt
Where you will parse the comma-delimited list afterwards. This is only
worth it if you expect a lot of encodings.
Q: How about actually answering the question?
A: I don't know how, short of parsing it manually.
* Small differences exist
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