Multiplying each element in the list by 2

Question

The question is Write a function called double_it() should iterate through the list and multiply each numeric element in the original list by 2 and reuturn integer representing the number of elements that were doubled.

Here is what I have..... the output is just repeating the list 2 times but not multiplying the values.

def main():
    original_list = [input("Enter a list of numbers: ")]
    double_it(original_list)

def double_it(new_list):
    for index in range(len(new_list)):
        new_list[index] *= 2
        print new_list

main()

Answer 1

Your problem looks like an error with handling the input. The raw_input function should generally be preferred over input.

I'll defer to this Stack Overflow question: https://stackoverflow.com/questions/4663306/how-can-i-get-a-list-as-input-from-the-user-in-python

As for the doubling part, there are a few ways to do this that might be worth knowing about, to fully explore python.

Iterative

>>> originalList = [1, 2, 3, 4, 5]
>>> newList = []
>>> for item in originalList:
...     newList.append(item*2)
... 
>>> print(newList)
[2, 4, 6, 8, 10]

List Comprehensions

>>> originalList = [1, 2, 3, 4, 5]
>>> newList = [item*2 for item in originalList]
>>> print(newList)
[2, 4, 6, 8, 10]

Maps

>>> def double(x): return 2*x
... 
>>> originalList = [1, 2, 3, 4, 5]
>>> newList = list(map(double, originalList))
>>> print(newList)
[2, 4, 6, 8, 10]

The python docs around this stuff are all quite good, and an excellent learning resource.

Answer 2

Your double_it() method works fine, just modify this line

original_list = [input("Enter a list of numbers: ")]

to

original_list = input("Enter a list of numbers: ")

Why? Because input() will evaluate the list you enter as a list , so you can work with it as a list, try printint the type :

a = input("Enter a list of numbers: ")
print type(a)

Enter a list of numbers: [1,2,3]
<type 'list'>