How to pass an entire list as command line argument in Python?

Question

I was trying to pass two lists containing integers as arguments to a python code. But sys.argv[i] gets the parameters as a list of string.

Input would

Answer 1

No, there is no way pass a list in a command line argument. Command line arguments are always string. But there is a better way to convert it to list. You can do it like that:

import ast

A = ast.literal_eval(strA)
B = ast.literal_eval(strB)

Answer 2

Why not:

python foo.py 1,2,3,4 5,6,7,8  

Much cleaner than trying to eval python and doesn't require your user to know python format.

import sys

list1 = sys.argv[1].split(',')
list2 = [int(c) for c in sys.argv[2].split(',')]  # if you want ints

Answer 3

Command line arguments are always passed as strings. You will need to parse them into your required data type yourself.

>>> input = "[2,3,4,5]"
>>> map(float, input.strip('[]').split(','))
[2.0, 3.0, 4.0, 5.0]
>>> A = map(float, input.strip('[]').split(','))
>>> print(A, type(A))
([2.0, 3.0, 4.0, 5.0], <type 'list'>)

There are libraries like argparse and click that let you define your own argument type conversion but argparse treats "[2,3,4]" the same as [ 2 , 3 , 4 ] so I doubt it will be useful.

edit Jan 2019 This answer seems to get a bit of action still so I'll add another option taken directly from the argparse docs.

You can use action=append to allow repeated arguments to be collected into a single list.

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', action='append')
>>> parser.parse_args('--foo 1 --foo 2'.split())
Namespace(foo=['1', '2'])

In this case you would pass --foo ? once for each list item. Using OPs example: python filename.py --foo 2 --foo 3 --foo 4 --foo 5 would result in foo=[2,3,4,5]

Answer 4

I tested this on my end, and my input looks like this:

python foo.py "[1,2,3,4]" "[5,6,7,8,9]"

I'm doing the following to convert the two params of interest:

import ast
import sys

list1 = ast.literal_eval(sys.argv[1])
list2 = ast.literal_eval(sys.argv[2])

Answer 5

You can also do the following:

say, you have foo.py :

import json
import sys
data = json.loads(sys.argv[1])
print data, type(data)

Then if you run the above as : python foo.py "[1,2,3]"

Output:

[1, 2, 3] <type 'list'>

Answer 6

You have to escape:

python some.py \[2,3,4,5\] \[1,2,3,4\]

some.py

import sys

print sys.argv[1]
print sys.argv[2]

this gives me:

[2,3,4,5]
[1,2,3,4]

UPDATE:

import sys
import ast

d = ast.literal_eval(sys.argv[1])
b = ast.literal_eval(sys.argv[2])

for a in d:
    print a

for e in b:
    print e

first will give:

2
3
4
5

and second will give

1
2
3
4