problem with random_item function challenge.

Hi, I am trying to solve this challenge, and regardless how many methods I use, it still doesn't work. The first problem I meet is NameError. I know I get that error because I haven't defined 'x' argument yet. so I try several ways to define it like use str() or list() or [] but still got the error message.

So here is the challenge

You've seen how random.choice() works. It gets a random member from an iterable (like a list or a string).

I want you to try and reproduce it yourself.

First, import the random library.

Then create a function named random_item that takes a single argument, an iterable. Then use random.randint() to get a random number between 0 and the length of the iterable, minus one. Return the iterable member that's at your random number's index.

I am very appreciated if you can tell what I did wrong and how I can fix it.

Thank you

# EXAMPLE
# random_item("Treehouse")
# The randomly selected number is 4.
# The return value would be "h"
import random
def random_item(x):
    x = []
    random_number = random.randint(0,len(x)-1)
    index = x[random_number]
    return index