Pass a list to function with variable number of args in python [duplicate]

Question

I have to write a simple function that takes variable number of arguments and prints the sum, something simple like(ignoring error checks):

def add(*params):
    sum = 0
    for num in params:
        sum += num
    print(sum)

I have to call the script and give it arguments that will then be used in the function. I get these arguments like this:

import sys
sys.argv[1:]

But that's an array and sending it to add would just mean passing 1 argument that is a list. I'm new to Python so maybe all of this sounds stupid, but is there any way to pass these arguments to the function properly?

you now about builtin sum() I assume? add() is already a function too for adding two values, so it's a bad name choice here — Chris_Rands
– Chris_Rands, Commented Nov 12, 2018 at 13:43
@Chris_Rands I have to write the function myself for a small assignment. And yeah I named them in my language just wrote the english version here, didn't know add was already a thing but the editor highlights these stuff so I know not to use keywords. — Angelo
– Angelo, Commented Nov 12, 2018 at 13:47

timgeb · Accepted Answer · 2018-11-12 13:45:07Z

9

Yes, just unpack the list using the same *args syntax you used when defining the function.

my_list = [1,2,3]
result = add(*my_list)

Also, be aware that args[1:] contains strings. Convert these strings to numbers first with

numbers = [float(x) for x in args[1:]]

or

numbers = map(float, args[1:]) # lazy in Python 3

before calling add with *numbers.

Short version without your add function:

result = sum(map(float, args[1:]))

answered Nov 12, 2018 at 13:45

timgeb

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rjmurt · Accepted Answer · 2018-11-12 13:46:42Z

1

You should use the argument unpacking syntax:

def add(*params):
    sum = 0
    for num in params:
        sum += num
    print(sum)

add(*[1,2,3])
add(*sys.argv[1:])

Here's another Stack Overflow question covering the topic

answered Nov 12, 2018 at 13:46

rjmurt

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