Customize help output from optparse (or argparse)

[Karim]

On 05/12/2011 10:22 PM, Thomas 'PointedEars' Lahn wrote:
> Thorsten Kampe wrote:
>
>> I'm using optparse for a little Python script.
>>
>> 1. The output from "--help" is:
>> """
>> Usage: script.py<arg>
>>
>> script.py does something
>>
>> Options:
>>    -h, --help   show this help message and exit
>> """
>>
>> I would prefer to have the description before the usage, like...
>> """
>> script.py does something
>>
>> Usage: script.py<arg>
>>
>> Options:
>>    -h, --help   show this help message and exit
>> """
>>
>> 2. The output from "--doesnotexit" is:
>> """
>> Usage: script.py<arg>
>>
>> script.py: error: no such option: --doesnotexist
>> """
>>
>> I would prefer to have the error first, then the usage and additionally
>> the options, like...
>> """
>> script.py: error: no such option: --doesnotexist
>>
>> Usage: script.py<arg>
>>
>> Options:
>>    -h, --help   show this help message and exit
>> """
>>
>> Is that possible with either optparse or the "new kid on the block"
>> argparse. If so how?
> You can easily have #1 with optparse.OptionParser(usage="…")¹, but optparse
> is deprecated in favor of argparse.ArgumentParser.  I do not think you can
> have #2 with either optparse or argparse: OptionParser() would print the
> error message last, and ArgumentParser() would not print the description
> on error.  Subclassing ArgumentParser might be feasible, though.
>
> ______
> ¹<http://PointedEars.de/devel/tools/text/odfinfo/>

Please find documentation to configure help in ArgumentParser BUT for 
argparse module:

- HelpFormatter, RawDescriptionHelpFormatter, RawTextHelpFormatter,
   50         ArgumentDefaultsHelpFormatter -- Formatter classes which
   51         may be passed as the formatter_class= argument to the
   52         ArgumentParser constructor. HelpFormatter is the default,
   53         RawDescriptionHelpFormatter and RawTextHelpFormatter tell 
the parser
   54         not to change the formatting for help text, and
   55         ArgumentDefaultsHelpFormatter adds information about 
argument defaults
   56         to the help.

So It seems easy to a different pass formatter_class to ArgumentParser. 
You can inherite
from HelpFormater class but you have to know the implementation details:
File is located at <python install>/lib/python2.7/argparse.py

Cheers
Karim