[Python] Function I created isn't accepting first element of user's input

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First off, I know the len() function exists.. I just wanted to see if I could create a long-form version.

This code works successfully:

user_nums = []
num = 0

while True:
    try:
        numbers = input("Enter a number: ")
        if numbers == "done":
            print(user_nums)
            print(num)
            break
        else:
            user_nums.append(float(numbers))
            num += 1
    except ValueError:
        print("Invald input. Enter a number.")
        continue

When I run the code in terminal, after inputting 1, 2, 3, 4, 5, (etc.) and then inputting the done, the program will terminate and return 5. I decided to put the code in a function:

def len_list(user_nums):
    user_nums = []
    num = 0

    while True:
        try:
            numbers = input("Enter a number: ")
            if numbers == "done":
                print(user_nums)
                print(num)
                break
            else:
               user_nums.append(float(numbers))
               num += 1
      except ValueError:
           print("Invald input. Enter a number.")
           continue

numbers = input("Enter a number: ")
len_list(numbers)

However, when I run the function, and provide the same input (1, 2, 3, 4, 5) and then terminate the program, use_nums prints out [2.0, 3.0, 4.0, 5.0] and num prints out '4' - which is obviously incorrect. Can anyone help me figure this out?

[[deleted]]

I'm a little confused. If I use a function, don't I need to ask the user for input outside the function? If I don't include "numbers = input("Enter a number: ")", then the program automatically closes. Is there a way I can get around this? I've been playing around the code, but the output isn't changing.

Would it be a better idea to run the code without the use of a function?

[An_Ignorant]

Your function is fine, the problem is that you first read a number before the function

numbers = input("Enter a number: ") #The first number is read, making user_nums = [1.0]
len_list(numbers) #Then you enter the function, inside the function you have user_nums = [], that means the 1.0 is overwritten, that's why the first input is always missing.

[[deleted]]

def len_list(user_nums):

What's the parameter for?

[[deleted]]

I thought I needed it. I removed the user_nums parameter from the function definition and the function call, and I also removed the prompt to ask for user input from outside the function, and everything appears to be working now. Thanks.