I am having a hard time understanding why this is...

Hi Christopher,

There's a few things going on here, but it sounds like you're just asking for clarity on the shredder() function. I've added some comments to all of the code that might also help.

# create a list of names and populate it with 4 items
turtles = ["Michelangelo", "Leonardo", "Raphael", "Donatello"]

# a function that takes a list and replaces the first item if the list
# has more than one item already
def shredder(names):
        if len(names) >= 1:
                names[0] = "Bebop"

# run the shredder function on the turtles list
shredder(turtles)

# loop through the turtles list, printing each item
for turtle in turtles:
        print("* " + turtle)

The shredder() function has a parameter names. When we call this function we provide an argument during the function call, this is then referred to by the paramter name within the function. In this code we pass turtles as the argument, and the first statement is a conditional statement that checks its length. The turtles list has a length of 4, so it meets the if len(names) >= 1 condition. This if branch then executes names[0] = "Bebop" replacing the list item at index 0 with "Bebop".

Cheers,

Eric