Extract values from parse.add_argument in Argparse - python

Question

I am using Argparse as a means to command line utility execution. I have various arguments defined ( couple of them shown below ). I have a requirement to store argument name, help, type in the database in their respective columns.

I am not sure how to extract these three from each parse.add_argument and save it in some array/list. If you can share any inputs, that would be helpful.

     parser.add_argument("num",help="The fibnocacci number to calculate:", type=int)  # how to take the strings on the command line and turn them into objects
     parser.add_argument("-f","--file",help="Output to the text file",action="store_true")

hpaulj · Accepted Answer · 2016-04-03 02:57:08Z

1

Others think you want the results of parsing the commandlline, the values from the args namespace. But I suspect you want the Action object defined by the add_argument method

In an interactive shell I can define a parser as:

In [207]: parser=argparse.ArgumentParser()

In [208]: arg1= parser.add_argument("num",help="The fibnocacci number to calculate:", type=int) 

In [209]: arg2=parser.add_argument("-f","--file",help="Output to the text file",action="store_true")

In [210]: arg1
Out[210]: _StoreAction(option_strings=[], dest='num', nargs=None, const=None, default=None, type=<type 'int'>, choices=None, help='The fibnocacci number to calculate:', metavar=None)

In [211]: arg2
Out[211]: _StoreTrueAction(option_strings=['-f', '--file'], dest='file', nargs=0, const=True, default=False, type=None, choices=None, help='Output to the text file', metavar=None)

In [212]: parser._actions
Out[212]: 
[_HelpAction(option_strings=['-h', '--help'], dest='help', nargs=0, const=None, default='==SUPPRESS==', type=None, choices=None, help='show this help message and exit', metavar=None),
 _StoreAction(option_strings=[], dest='num', nargs=None, const=None, default=None, type=<type 'int'>, choices=None, help='The fibnocacci number to calculate:', metavar=None),
 _StoreTrueAction(option_strings=['-f', '--file'], dest='file', nargs=0, const=True, default=False, type=None, choices=None, help='Output to the text file', metavar=None)]

add_argument creates an Action subclass (based on action parameter). You can save this in your own variable, or find it in the _actions list of the parser.

Printing this shows some of its attributes, but you can examine, and even change more of them.

In [213]: arg1.help
Out[213]: 'The fibnocacci number to calculate:'

In [214]: arg1.type
Out[214]: int

In [215]: arg1.dest
Out[215]: 'num'

In [217]: vars(arg1)
Out[217]: 
{'choices': None,
 'const': None,
 'container': <argparse._ArgumentGroup at 0x8f0cd4c>,
 'default': None,
 'dest': 'num',
 'help': 'The fibnocacci number to calculate:',
 'metavar': None,
 'nargs': None,
 'option_strings': [],
 'required': True,
 'type': int}

You many need to examine the class definitions in the argparse.py file to understand these attributes.

edited Apr 3, 2016 at 2:57

answered Apr 3, 2016 at 2:50

hpaulj

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2 Comments

Goutam Over a year ago

when I do arg1.type i get <class 'int'> and not int?

hpaulj Over a year ago

I get that with print(arg1.type). int is both a class and a function that produces an integer.

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