optparse quirks

[kbriggs]

BPO	4278
Nosy	@loewis, @amauryfa, @agbuckley

^{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 = None
closed_at = <Date 2009-07-01.16:53:00.456>
created_at = <Date 2008-11-07.13:13:39.832>
labels = ['extension-modules', 'type-bug']
title = 'optparse quirks'
updated_at = <Date 2009-07-01.16:53:00.449>
user = 'https://bugs.python.org/kbriggs'

bugs.python.org fields:

activity = <Date 2009-07-01.16:53:00.449>
actor = 'amaury.forgeotdarc'
assignee = 'none'
closed = True
closed_date = <Date 2009-07-01.16:53:00.456>
closer = 'amaury.forgeotdarc'
components = ['Extension Modules']
creation = <Date 2008-11-07.13:13:39.832>
creator = 'kbriggs'
dependencies = []
files = []
hgrepos = []
issue_num = 4278
keywords = []
message_count = 4.0
messages = ['75602', '77499', '82753', '89990']
nosy_count = 4.0
nosy_names = ['loewis', 'amaury.forgeotdarc', 'kbriggs', 'andybuckley']
pr_nums = []
priority = 'normal'
resolution = 'works for me'
stage = None
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue4278'
versions = ['Python 2.7']

[kbriggs]

I got the message:

optparse.OptionError: invalid long option string '-T0': must start with
--, followed by non-dash

This is bad - the real error was that I gave a short option which did
not have a single letter.

Also, it seems that add_option('--height-of-plot','-h') is not allowed,
because -h can only go with --help. How do I override this?

Keith

[loewis]

No patch proposed yet, so retargetting to trunk.

[agbuckley]

Are these really bugs? The first message just reports the error the
other way around from how you view it: you are thinking of "-TO" as a
two-character "short option", optparse thinks of it as a two-character
long option which is missing a dash. I would side with optparse's
definition, since the point of short options is that they can be
combined under a single dash --- a multi-character option can't do that,
and so can't be "short" by definition.

In both this and the "-h" issue, optparse is reasonably enforcing a UI
convention as well as providing parsing facilities. That uniformity of
UI behaviour is a design goal is made explicit in the documentation.
Using optparse means that users can rely on "-h" to give them help
documentation, which IMO is a very useful convention to respect. And the
splitting of long and short options by whether they are single character
(and hence can be combined) or multi-character (hence uncombinable, but
good for less-used options without eating up the alphabetic option
namespace) is another nice convention which optparse enforces.

-1 from me: I think the existing behaviours are good, largely *because*
they aren't flexible.

[amauryfa]

• For the -h option, you may add "add_help_option=False" when creating
  the Optparse object

• concerning the error message: every parser that tries to give
  meaningful error messages has to guess what the user really meant. The
  exact text is really an implementation detail.