How to get more than one input from a single input() function in Python?

Question

I've learnt that using * before a custom function argument, I can pass more than one or uncertain amount of data as the argument. For adding numbers function or something like that I can pass unlimited amount of data when I call the function. But I want to get these numbers from user. As I don't know how many numbers I'm gonna get, I can't declare variable for each of them previously. Now, how can I get many numbers as input and add them together with a custom function? My idea is quite similar to a calculator in real life.

Here is my code. I want to get the numbers as input instead of putting them manually while writing code. I will be grateful if anyone gives me the code about what I was trying to do.

def add_number(*args):
    total = 0
    for number in args:
        total += number
    print(total)


add_number(2, 3, 6, 9)

Answer 1

You say you need to use a single input. In this case we can split our input using the .split(separator) method of the string, which returns a list of parts of the given string. separator argument is optional: if the user enters the numbers separated by whitespace characters, you don't need to pass this argument, otherwise you need to pass a separator.

numbers = input("Enter the numbers... ").split()  # if numbers are separated by any of whitespace characters ("1 2 3 4")

numbers = input("Enter the numbers... ").split(", ")  # if numbers are separated by a comma and a space ("1, 2, 3, 4")

Note: I'll suppose your numbers are separated by a whitespace character in the next part of answer.

If we would like to print the numbers list, we will get this output:

>>> numbers = input("Enter the numbers... ").split()
Enter the numbers... 1 2 3 4
>>> print(numbers)
['1', '2', '3', '4']

As we can see all the items of our list are strings (because of the quotation marks: '1', not 1). If we'll try to concatenate them together we'll get something like this: '1234'. But if you want to concatenate them together as numbers, not strings, we'll need to convert them to int (for integers) or float (for non-integer numbers) type. If we have one number, it can be done easily: int(number). But we have got a list of numbers and we need to convert every element to int.

We can use the map(func, iterable) function. It will apply the func to every item of iterable and return a map object - an iterator (NOT a list!):

numbers = map(int, numbers)

Note: if we would like to represent it as a list, we can simply do:

numbers = list(map(int, numbers))

though it is not necessary here.

And now we can throw all the numbers to your add_number(*args) function using the asterisk (*) - pack them:

add_number(*numbers)

Note: you can also use sum function to add all the numbers from iterable - in this case, you don't need to pack the args, because it gets a single iterable of numbers:

sum_ = sum(numbers)

And then let's print our result:

print(sum_)

Important Note: sum(iterable) returns the sum of the numbers and prints nothing, while your add_number(*args) function returns None and prints the number (it is not the same thing!). Here is a good, detailed explanation.

Here is the whole code what we've written:

def add_number(*args):
    total = 0
    for number in args:
        total += number
    print(total)

numbers = input("Enter the numbers... ").split()  # if numbers are separated by any of whitespace characters ("1 2 3 4")
numbers = map(int, numbers)
add_number(*numbers)

And here is a one-liner that does the same thing - it uses sum function instead of the add_number and hence doesn't require anything else in the code:

print(sum(map(int, input("Enter the numbers... ").split())))