Python parse arguments from command line

Question

I have a question regarding passing arguments in Python.for Ex: in the script i am expecting arguments like

1.python run.py -create vairbale1 -reference variable2 many more variables
2.python run.py -get -list variable many more variable

How can i enfore this in the script using optparse or getopt and if the arguments are invalid The i need to print Invalid arguments

 from optparse import OptionParser
 parser = OptionParser()

• Lee Netherton: FYI: The optparse module has been depreciated. As of 2.7 you'll probably want to use the argparse module: docs.python.org/library/argparse.html#module-argparse

Answer 1

here's a snippet I've used. I worked for me, though you might have to change the parameter types.

parser = OptionParser()
parser.add_option('-n', '--db_name', help='DB Name (comma separated if multiple DBs - no spaces)')
parser.add_option('-H', '--db_host', help='DB host (comma separated if multiple DBs - no spaces)')
parser.add_option('-p', '--db_port', help='DB port (optional)')
parser.add_option('-u', '--db_user', help='DB user')
parser.add_option('-w', '--db_pass', help='DB password')
parser.add_option('-o', '--output-file', help='output file')
options, args = parser.parse_args()
errors = []
error_msg = 'No %s specified. Use option %s'
if not options.db_name:
 errors.append(error_msg % ('database name', '-n'))
if not options.db_host:
 errors.append(error_msg % ('database host', '-H'))
if not options.db_user:
 errors.append(error_msg % ('database user', '-u'))
if not options.db_pass:
 errors.append(error_msg % ('database password', '-w'))
if not options.output_file:
 errors.append(error_msg % ('output file', '-o'))
if errors:
 print '\n'.join(errors)
 sys.exit(1)

• Rajeev: Canu please explain for any one example how are you trying to use it
• Nostradamnit: You run the script python blah.py -n dbname - H dbhost -p 8080 -u dbuser -w dbpass -o path_to_file then in the code you can access the values passed using options.db_name for example
• Rajeev: K.Along with -n dbname if i have to pass one more parameter. How can i change it in the code? parser.add_option('-n', '--db_name','var1', help='DB Name (comma separated if multiple DBs......)
• Nostradamnit: The extra variables will be in the args variable after you call parser.parse_args()
• brandeded: thanks. This got me going well... I just wanted to mention that you can easily print the help info provided with parser.format_help().strip() then exit with sys.exit(0) to match the native function.

Answer 2

You can use custom action to validate your data like

import argparse
import re
class ValidateEmailAction(argparse.Action):
 ''' 
 Function will not validate domain names.
 e.g. [email protected] is valid here.
 '''
 def __call__(self, parser, namespace, values, option_string=None):
 super(argparse.Action, self).__call__(parser, namespace, values,
 option_string=option_string)
 email = values
 pattern = "^([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})$"
 if not re.match(pattern, email) != None:
 raise AttributeError
parser = argparse.ArgumentParser()
parser.add_argument('-e', '--email', action=ValidateEmailAction, help='Enter valid email.')

Also check the custom action on http://docs.python.org/dev/library/argparse.html#action

• Ciasto piekarz: your code is throwing error even if i enter correct email address: super(argparse.Action, self).__call__(parser, namespace, values, AttributeError: 'super' object has no attribute '__call__'
• NPatel: This might be new change. I will update you after checking new changes in argparse.Action