5

I want to make a script in python and then run it from the command line. The script is called test.py and the command to run it is:

python3 test.py John Jackson

Here is the expected output:

John Jackson

And here is the python script I made:

class person:

    def __init__(self, first, last):
        self.firstname = first
        self.lastname = last

    def get_first(self):
        return self.firstname

    def get_last(self):
        return self.lastname

import argparse

def main():
    parser = argparse.ArgumentParser()
    parser.add_argument('first')
    parser.add_argument('last')
    args = parser.parse_args()
    c1 = person(args.first, args.last)
    print(c1)

But the problem is when I run the script from the command line using the mentioned command, it returns nothing. Do you know how to fix it and get the expected output?

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2
  • I fixed that but still no results. Commented May 18, 2019 at 12:21
  • Python does not automatically run a function called main. Some other languages may do that, but not Python. Commented May 18, 2019 at 16:10

3 Answers 3

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5

You defined your main() function but did not call it.

Add this at the end of your script:

if __name__ == "__main__":
    main()

See What does if __name__ == “__main__”: do?.

Then, c1 is the person instance, which would print: 

$ python3 test.py John Jackson
<__main__.person object at 0x104907ef0>

You need to call get_first() and get_last() to get the correct output:

print(c1.get_first(), c1.get_last())
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Comments

2

I am not sure if you are calling your main function while running the script.

Add

if __name__ == "__main__":
    main()

And override __str__ function of the person class to print first name and last name while passing class as argument to print.

def __str__(self):
    return self.firstname + ' ' + self.lastname

The whole code goes like this

import argparse

class person:

    def __init__(self, first, last):
        self.firstname = first
        self.lastname = last

    def get_first(self):
        return self.firstname

    def get_last(self):
        return self.lastname

    def __str__(self):
        return self.firstname + ' ' + self.lastname

def main():
    parser = argparse.ArgumentParser()
    parser.add_argument('first')
    parser.add_argument('last')
    args = parser.parse_args()
    c1 = person(args.first, args.last)
    print(c1)

if __name__ == '__main__':
    main()
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0

Your script is unnecessarily complex, a much (much) simpler way to achieve this is to use the argv property of the sys module then separate the (string) argument using split, like this:

import sys

name = sys.argv[1].split(" ")

if len(name) != 2:
  raise ValueError("Invalid first and last name, try using \"John Jackson\" instead.")

[first_name, last_name] = name
print(first_name, last_name)

You don't even need to raise an error:

import sys

name = sys.argv[1].split(" ")

if len(name) == 2:
  [first_name, last_name] = name
  print(first_name, last_name)

Then when you run the script like this:

python3 filename.py "John Jackson"

You should get the following output:

John Jackson

Good luck.

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