how to use python argparse optional argument

Question

my python code looks like this

parser.add_argument("-c","--configFile",action ='store_true',\
 help='I am here one travel')

the idea is when running with -c option, I could have select to use my special config file. However, I issue my command python mypython.py -c myconfig, I am getting unrecognized argument: myconfig. What am I missing?

Answer 1

As Adam mentioned, you'll want to change your parser's "action", as stated in the docs.

But it sounds like you want to indicate whether that special config is active, or not. In which case, using action='store_true' or action='store_false' would be correct. You just won't pass the myconfig argument.

parser = argparse.ArgumentParser(description='So something')
parser.add_argument(
 '-c',
 '--c',
 dest='enable_config',
 action='store_true',
 required=False,
 help='Enable special config settings',
)

• PChao: I am kind of struggling here. I i enter my code here:
• PChao: if I issue the command "Python myprog.py -c user_config_file." How do I refer to the value user_config_file? I need to do something with it. Thanks!
• Patrick Beeson: If you want to specify a filename, you'll need to capture it as an argument. For instance, here I am capturing a list of arguments for a parser: parser.add_argument( dest='filenames', metavar='filename', nargs='*', help='list of files to compress within a specified directory', ) Note the nargs argument allows for an unlimited number of filenames to be passed. You'll want to limit this to one file for your use. Also note that there is no action needed for add_argument since the default action is store, which captures the argument's value.

Answer 2

"-c" will store True or False, so why are you passing a value (myconfig) to it? You would call it as:

python mypython.py -c

If you want -c to take an argument, then it shouldn't have the action store_true.