Is there way to input a list to a Python program in the command line?

Question

I would like to pass a list as a parameter using the command line, for example:

$python example.py [1,2,3] [4,5,6]

I want the first list [1,2,3] to be first_list and [4,5,6] to be second_list. How can I do this?

Either use a string format or use some form of eval (extremely dangerous - this is user input!). So - use a string format of a list (example.py 1,2,3 3,4,5). — Reut Sharabani
– Reut Sharabani, Commented Sep 12, 2015 at 23:54
@ReutSharabani I cannot do that, the program will be tested as shown in my question. — Julia
– Julia, Commented Sep 12, 2015 at 23:56
You can use ast.literal_eval. eval is probably fine for a test program that only you will run. — Colonel Thirty Two
– Colonel Thirty Two, Commented Sep 12, 2015 at 23:58
This means you'll have to parse the input. If it's just a stringified list you may be able to use the json module on each of the arguments. I'm not sure about the security literal_eval offers so I'm not going to offer it :-) — Reut Sharabani
– Reut Sharabani, Commented Sep 12, 2015 at 23:58
There is an extended code example of using ast.literal_eval to pass lists, dicts and tuples to Python on the command line at stackoverflow.com/questions/7605631/…, see answer by the-wolf. — user4322779
– user4322779, Commented Sep 13, 2015 at 2:13

hilberts_drinking_problem · Accepted Answer · 2015-09-13 00:16:38Z

1

import ast
import sys

for arg in sys.argv:
    try:
        print sum(ast.literal_eval(arg))
    except:
        pass

In command line:

   >>= python passListAsCommand.py "[1,2,3]"
    6

Be careful not to pass anything malicious to literal_eval.

answered Sep 13, 2015 at 0:16

hilberts_drinking_problem

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Community · Accepted Answer · 2017-05-23 11:51:50Z

1

[ might be a shell meta-character. You could drop [] as @Reut Sharabani suggested:

$ python example.py 1,2,3 4,5,6

It is easy to parse such format:

#!/usr/bin/env python3
import sys

def arg2int_list(arg):
    """Convert command-line argument into a list of integers.

    >>> arg2int_list("1,2,3")
    [1, 2, 3]
    """
    return list(map(int, arg.split(',')))

print(*map(arg2int_list, sys.argv[1:]))
# -> [1, 2, 3] [4, 5, 6]

edited May 23, 2017 at 11:51

CommunityBot

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answered Sep 13, 2015 at 18:27

jfs

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Comments

trishnag · Accepted Answer · 2015-09-13 16:37:47Z

0

import sys
def command_list():
    l = []
    if len(sys.argv) > 1:
        for i in sys.argv[1:]:
            l.append(i)
    return l
print(command_list())

In the command line

$ python3 test105.py 1,2,3 4,5,6
['1,2,3', '4,5,6']

answered Sep 13, 2015 at 16:37

trishnag

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1 Comment

Anshul Goyal Over a year ago

I don't think that is what the OP is trying to do, '1,2,3' is still a string (and not a list)

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