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getopt with negative numbers?

Is there an easy way to use getopt and still allow negative numbers as
args? I can easily write a workaround (pre-process the tail end of
the arguments, stripping off any non-options including negative
numbers into a separate sequence and ignore the (now empty) args list
returned by getopt, but it would seem this is such a common
requirement that there would be an option to treat a negative value as
an argument. Note that this is only a problem if the first non-option
is a negative value, since getopt stops processing options as soon as
it identifies the first argument value.

Alternatively, does optparse handle this? I haven't used optparse (I
know it is more powerful and OO, but you tend to stick with what you
know, especially when it is part of my normal python programming
template), but if it handles negative numbers I'm willing to learn it.

Sep 27 '07
20 5837
Carl Banks wrote:
On Sep 28, 9:51 am, Steven Bethard <steven.beth... @gmail.comwrote :
>It was decided that practicality beats purity here. Arguments with
leading hyphens which look numeric but aren't in the parser are
interpreted as negative numbers. Arguments with leading hyphens which
don't look numeric and aren't in the parser raise errors. Sure, it's not
the pure answer, but it's the practical answer: "-123" is much more
likely to be a negative number than an option.

What if (for example) you define a option "-3", and also accept
numerical arguments on the command line. Then you could get sudden
unexpected behavior if you input the wrong number:

"./hello -1" works ok.
"./hello -2" works ok.
"./hello -3" ... whoops, now the negative number is suddenly an

Granted, it would be stupid for a program to do that, but it suggests
to me that it's probably a good idea to treat all negative numbers the
same. I.e. if there are any numerical options, then all negative
numbers are treated as options. If there are none, then negative
numbers are treated as numbers.
That's probably a good guideline. Anyone mixing numeric flags with
negative number arguments is asking for an exception of some sort. ;-)
I'm going to let it sit for a while and think about it, but I'll
probably make that change in the next release.

Sep 28 '07 #21

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