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Basic Introduction to Use Arguments With Argparse on Python

I used to work a lot with sys.argv for using arguments in my applications, until I stumbled upon the argparse module! (Thanks Donovan!)

What I like about argparse, is that it builds up the help menu for you, and you also have a lot of options, as you can set the argument to be required, set the datatypes, addtional help context etc.

The Basic Demonstration:

Today we will just run through a very basic example on how to use argparse:

  • Return the generated help menu
  • Return the required value
  • Return the additional arguments
  • Compare arguments with a IF statement

The Python Argparse Tutorial Code:

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import argparse

parser = argparse.ArgumentParser(description='argparse demo')
parser.add_argument('-w', '--word', help='a word (required)', required=True)
parser.add_argument('-s', '--sentence', help='a sentence (not required)', required=False)
parser.add_argument('-c', '--comparison', help='a word to compare (not required)', required=False)
args = parser.parse_args()

print("Word: {}".format(args.word))

if args.sentence:
  print("Sentence: :{}".format(args.sentence))

if args.comparison:
  if args.comparison == args.word:
      print("Comparison: the provided word argument and provided comparison argument is the same")
  else:
      print("Comparison: the provided word argument and provided comparison argument is NOT the same")

Seeing it in action:

To return a usage/help info, run it with the -h or --help argument:

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$ python foo.py -h
usage: foo.py [-h] -w WORD [-s SENTENCE] [-c COMPARISON]

argparse demo

optional arguments:
  -h, --help            show this help message and exit
  -w WORD, --word WORD  a word (required)
  -s SENTENCE, --sentence SENTENCE
                        a sentence (not required)
  -c COMPARISON, --comparison COMPARISON
                        a word to compare (not required)

For this to work, the application is expecting the word argument to run, as we declared it as required=True:

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$ python foo.py -w hello
Word: hello

Now to use the arguments that is not required, which makes it optional:

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$ python foo.py -w hello -s "hello, world"
Word: hello
Sentence: :hello, world

We can also implement some if statements into our application to compare if arguments are the same (as a basic example):

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$ python foo.py -w hello -s "hello, world" -c goodbye
Word: hello
Sentence: :hello, world
Comparison: the provided word argument and provided comparison argument is NOT the same

We can see that the word and comparison arguments are not the same. When they match up:

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$ python foo.py -w hello -s "hello, world" -c hello
Word: hello
Sentence: :hello, world
Comparison: the provided word argument and provided comparison argument is the same

This was a very basic demonstration on the argparse module.

Resource: