Better way of programming

Question

Im trying to write a script using python language(abc.py). I need to take few command line arguments while executing the script.

say -m, -p are my arguments. I need to have a string beside these options. ex:

 1. $> python abc.py -m 'first' -p 'second' {correct}
 2. $> python abc.py -p 'first' -m 'second' {correct}
 3. $> python abc.py -m -p 'first' 'second' {Incorrect}
 4. $> python abc.py 'first' -p 'second' {Incorrect}

I have more such arguments like -m, -p. What is the best algorithm to check if the passed arguments are in the correct format. I am unable think other than the method maintaining the previous argument and check based on it.

Thanks for you help in advance

Anji

Thorn · Accepted Answer · 2012-04-29 07:28:44Z

7

You don't need to do that yourself, Python as they say comes with batteries included. The standard library has two modules for parsing command line arguments: argparse for python 2.7+ and optparse for 2.6 or older. Documentation for those has good usage examples, too.

answered Apr 29, 2012 at 7:28

Thorn

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2 Comments

qrtt1 Over a year ago

2.6 and older can install by easy_install argparse as well :)

Anji Over a year ago

thanks for throwing light on me. SO will never disappoint me :)

arhimmel · Accepted Answer · 2012-04-29 07:24:52Z

1

use the argparse module http://docs.python.org/library/argparse.html#module-argparse

answered Apr 29, 2012 at 7:24

arhimmel

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Comments

dstromberg · Accepted Answer · 2012-04-29 21:30:14Z

The modules are good, though they don't play nice with pylint, so I tend to do my own argument parsing to get better error detection. EG:

red = False
blue = False
green = False
red_weight = 1.0
green_weight = 1.0
blue_weight = 1.0

while sys.argv[1:]:
   if sys.argv[1] in [ '-h', '--help' ]:
      usage(0)
   elif sys.argv[1] in [ '-r', '--red' ]:
      red = True
   elif sys.argv[1] in [ '-b', '--blue' ]:
      blue = True
   elif sys.argv[1] in [ '-g', '--green' ]:
      green = True
   elif sys.argv[1] == '--red-weight':
      red_weight = float(sys.argv[2])
      del sys.argv[1]
   elif sys.argv[1] == '--green-weight':
      green_weight = float(sys.argv[2])
      del sys.argv[1]
   elif sys.argv[1] == '--blue-weight':
      blue_weight = float(sys.argv[2])
      del sys.argv[1]
   else:
      sys.stderr.write('%s: unrecognized option: %s\n' % (sys.argv[0], sys.argv[1]))
      usage(1)
   del sys.argv[1]

HTH

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