CODEWITHSUNDEEP
pythonloopscommand-line
FootOfGork
FootOfGork

Reputation: 55

Command - line input

Im trying to take in a a set of numbers from the command line prompt and then have the program print back the smallest number, but I keep getting and index error saying that myArray = (sys.argv[1]) is out of range

 import sys
 from List import *

 def main(int,strings):
     myArray = (sys.argv[1])
     strings = myArray(sys.argv[1:])
     numbers = (int,strings)

     smallest = numbers[0]
     for i in range(1,len(numbers),1):
        if(numbers[i] < smallest):
            smallest = numbers[i]
    print ("The smallest number is", smallest)


main

Upvotes: 0

Views: 68

Answers (2)

SethMMorton
SethMMorton

Reputation: 48725

An IndexError means you are trying to access an element of a list that doesn't exists. The sys.argv list contains in element 0 the name of the script, and in the other elements the command line arguments. So, if you call the script with 0 command line arguments, element 1 won't exist.

Here are two ways to handle this:

# Method one: check first:
if len(sys.argv) <= 1:
    sys.exit('You need to call this script with at least one argument')
myArray = (sys.argv[1]) # Why did you add the parenthesis?
...


# Method two: go for it and ask questions later
try:
    myArray = (sys.argv[1])
    ...
except IndexError:
    sys.exit('You need to call this script with at least one argument')

Upvotes: 1

alecxe
alecxe

Reputation: 473813

Don't reinvent the wheel and use argparse module. It's simple and readable:

import argparse

parser = argparse.ArgumentParser()
parser.add_argument("-l", "--list", nargs='+', type=int)

args = parser.parse_args()
print("The smallest number is %d" % min(args.list))

Here's what on the console:

$ python test.py -l 1 2 3 4 5
The smallest number is 1
$ python test.py --list 1 2 3 4 5
The smallest number is 1

Upvotes: 1

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