What is the best way to print the usage string ?

[Steven Bethard]

Leonel Gayard wrote:
> Hi all,
> 
> I had to write a small script, and I did it in python instead of
> shell-script. My script takes some arguments from the command line,
> like this.
> 
> import sys
> args = sys.argv[1:]
> if args == []:
>     print """Concat: concatenates the arguments with a colon (:) between 
> them
> Usage: concat arg1 [arg2...]
> Example: concat a b c prints \"a.jar:b.jar:c/\""""
>     sys.exit(1)
> print reduce(lambda x, y: x + ':' + y, sys.argv[1:])

The short answer is to use textwrap.dedent::

 >>> import textwrap
 >>> if True:
...     print textwrap.dedent('''\
...         Concat: concatenates the arguments with a colon (:) between
...         them
...         Usage: concat arg1 [arg2...]
...         Example: concat a b c prints "a.jar:b.jar:c/"''')
...
Concat: concatenates the arguments with a colon (:) between
them
Usage: concat arg1 [arg2...]
Example: concat a b c prints "a.jar:b.jar:c/"


You also might consider using an argument parsing like argparse[1] to 
build your usage string for you:

------------------------------ concat.py ------------------------------
import argparse

if __name__ == '__main__':
     parser = argparse.ArgumentParser(
         description='concatenates the arguments with a colon (:) '
                     'between them')
     parser.add_argument('args', metavar='arg', nargs='+',
                         help='one item to be concatenated')
     namespace = parser.parse_args()
     print ':'.join(namespace.args)
-----------------------------------------------------------------------


$ concat.py
usage: concat.py [-h] arg [arg ...]
concat.py: error: too few arguments

$ concat.py -h
usage: concat.py [-h] arg [arg ...]

concatenates the arguments with a colon (:) between them

positional arguments:
   arg         one item to be concatenated

optional arguments:
   -h, --help  show this help message and exit

$ concat.py a b c


Steve

[1] http://argparse.python-hosting.com/