Executing python script(having arguments) from shell script

Question

myfile.sh

#!/bin/bash
echo -e "\n starting python script"
python main.py arg1
echo -e "\n done"

This is not working.

Above file has given following error

starting python script
Traceback (most recent call last):
  File "main.py", line 97, in <module>
    main()
  File "main", line 80, in main
    header = "arg1: {}\n\n".format(sys.argv[1])
ValueError: zero length field name in format

done

main.py

...
...
def main():
    """ main function
    """

    header = "arg1: {}\n\n".format(sys.argv[1])
    ...
    ...


if __name__ == "__main__":

    if len(sys.argv) == 2:
        main()
    else:
        print "\n Invalid no. of arguments"
        print "\n Usage:"
        print "\n python {} <date>\n".format(sys.argv[0])
        exit(1)

Whats the correct syntax to call a python script having arguments from shell script ?

Could you please be a little more precise? Maybe with a toy example? — user189
– user189, Commented Aug 11, 2014 at 12:31
Yes it is correct, what do you mean for not working? bash throws an error, python throws an error? — enrico.bacis
– enrico.bacis, Commented Aug 11, 2014 at 12:32
What is your Python version? Could we please get the python script? — user189
– user189, Commented Aug 11, 2014 at 12:39
@user189 updated question with main.py contents and my python version is 2.6.2 — Patrick
– Patrick, Commented Aug 11, 2014 at 12:44
Change {} --> {0}, or maybe upgrade to 2.7 if possible. So this is not problem of calling python, but a rather a problem of using the wrong syntax for the your python version. — FredrikHedman
– FredrikHedman, Commented Aug 11, 2014 at 12:59

FredrikHedman · Accepted Answer · 2014-08-11 13:05:43Z

2

Your script should work fine. Here is a toy sample:

#!/bin/bash
echo -e "\n starting python script"
python main.py arg1 arg2 arg3
echo -e "\n done"

with main.py as

#!/usr/bin/env python
from __future__ import print_function
import sys

print("In python pgm called from shell script with args:")
for i, a in enumerate(sys.argv):
    print("argument {0} is {1}".format(i, a))

The error is probably caused by the '{}'. Need to have a recent enough python version for that to work (2.7 or better to be on the safe side...). Otherwise specify the positional argument numbers.

edited Aug 11, 2014 at 13:05

answered Aug 11, 2014 at 12:48

FredrikHedman

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Comments

Community · Accepted Answer · 2020-06-20 09:12:55Z

0

Yes, this is correct. Try this for example:

main.py

import sys
print sys.argv[1]

edited Jun 20, 2020 at 9:12

CommunityBot

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answered Aug 11, 2014 at 12:35

enrico.bacis

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