CODEWITHSUNDEEP
python
user3245142
user3245142

Reputation: 81

Can I incorporate sys.argv into this?

I am trying to create a simple script that will accept age as an argument to determine the appropriate fee for admission. (< 6 = Free; >= 7 and <=14 is $10; >=15 and <=59 is $15; >= 60 is $5)

I've managed to get the script to work if I input the age at the age = __ within the script, but I want to be able to pass in age as an argument in the Arguments box of the Run Script window. I think I should be able to use sys.argv but I haven't been able to figure out how. I suspect it has to do with some sort of disagreement between what sys.argv wants and what I'm providing--maybe a mismatch with strings and integers?

Any ideas?

# Enter age
age = 5

if age < 7:
    print ("Free Admission")

elif age < 15:
    print ("Admission: $10")

elif age < 60:
    print ("Admission: $15")

else:
    print ("Admission: $5")

Upvotes: 4

Views: 85

Answers (2)

zmo
zmo

Reputation: 24812

# here you import `sys` that enables access to `sys.argv`
import sys

# then you define a function that will embed your algorithm
def admission_fee(age):
    age = int(age)
    if age < 7:
        print ("Free Admission")
    elif age < 15:
        print ("Admission: $10")

    elif age < 60:
        print ("Admission: $15")

    else:
        print ("Admission: $5")

# if you call this python module from the command line, you're in `__main__` context
# so if you want to reuse your module from another code, you can import it!
if __name__ == "__main__":
    # here you use the first argument you give to your code, 
    # sys.argv[0] being the name of the python module
    admission_fee(sys.argv[1])

As Martijn says, you can use argparse module or I now prefer to use the docopt module which makes it easier and nicer to implement!

As an example of docopt use:

"""Usage: calcul_fee.py [-h] AGE

Gets the admission fee given the AGE

Arguments:
    AGE  age of the person

Options:
    -h --help"""

from docopt import docopt

def admission_fee(age):
    age = int(age)
    if age < 7:
        print ("Free Admission")
    elif age < 15:
        print ("Admission: $10")
    elif age < 60:
        print ("Admission: $15")
    else:
        print ("Admission: $5")

if __name__ == '__main__':
    arguments = docopt(__doc__)
    admission_fee(arguments.AGE)

Upvotes: 1

Martijn Pieters
Martijn Pieters

Reputation: 1122002

Sure, that's absolutely what you can do with sys.argv; just take into account that sys.argv[0] is the script name, and all values in it are strings:

import sys

if len(sys.argv) > 1:
    try:
        age = int(sys.argv[1])
    except ValueError:
        print('Please give an age as an integer')
        sys.exit(1)

else:
    print('Please give an age as a command line argument')
    sys.exit(1)

Python comes with the argparse module which makes parsing sys.argv arguments a little easier still:

import argparse

parser = argparse.ArgumentParser('Admission fee determination')
parser.add_argument('age', type=int, help='the age of the visitor')
args = parser.parse_args()

age = args.age

where age is already an integer. As an added bonus, your script is given a help text too:

$ python yourscript.py -h
usage: Admission fee determination [-h] age

positional arguments:
  age         the age of the visitor

optional arguments:
  -h, --help  show this help message and exit

and automatic error feedback if age is not given or not an integer.

Upvotes: 4

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