CODEWITHSUNDEEP
pythonfunctionargv
diegus
diegus

Reputation: 1188

Check if sys.argv are defined inside a function

I would like to define a function that checks whether any argv were give to a command line, otherwise would print a string or return two strings. Here is the code:

import sys

def get_input():
    if len(sys.argv) > 1:
        path_input_text = sys.argv[1]
        path_basic_conf = sys.argv[2]
        return path_input_text, path_basic_conf
    elif len(sys.argv) == 1:
        print "Takes at least two arguments"
    else:
        print "No arguments entered"
        return 'file.txt', 'file.xml'

I try to call the function like this:

a,b = get_input()

It works when I give two arguments but it fails in the other two cases, i.e. the elif and else statements. How can I make it work? Should I be using the try/except statement? thanks

EDIT 1

when I try 1 args only:

IndexError: list index out of range

when I try with no args:

TypeError: 'NoneType' object is not iterable

In the case of 1 args given I would like to raise an error rather then returning None,None.

Upvotes: 0

Views: 3480

Answers (2)

Harsha Biyani
Harsha Biyani

Reputation: 7268

argv[0] is the script name (it is operating system dependent whether this is a full pathname or not). If the command was executed using the -c command line option to the interpreter, argv[0] is set to the string '-c'. If no script name was passed to the Python interpreter, argv[0] is the empty string. (reference : https://docs.python.org/2/library/sys.html)

Try this : 

import sys
def get_input():
    if len(sys.argv) > 2:
        #print (sys.argv[0])
        path_input_text = sys.argv[1]
        path_basic_conf = sys.argv[2]
        return path_input_text, path_basic_conf
    elif len(sys.argv) ==2:
        #print (sys.argv[0])
        print ("Takes at least two arguments")
        return None,None
    else:
        #print (sys.argv[0])
        print ("No arguments entered")
        return 'file.txt', 'file.xml'

a,b = get_input()
print (a)
print (b)

Output :

D:\>python so.py 1
Takes at least two arguments
None
None

D:\>python so.py
No arguments entered
file.txt
file.xml

D:\>python so.py 1 2
1
2

Upvotes: 2

Destrif
Destrif

Reputation: 2134

In one case you return nothing, you should return something: None for example.

elif len(sys.argv) ==1:
    print "Takes at least two arguments"

Should be:

elif len(sys.argv) ==1:
    print "Takes at least two arguments"
    return None,None

Your length should start at 2 not 1

if len(sys.argv) > 2:

Upvotes: 0

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