Problem with my pong game code

[Than999]

Hi, I am following a tutorial online: freecodecamp.org on Youtube. I am learning how to program a simple pong game in Python. However, when I go and execute my code the "left paddle" associated with the "w" key on my keyboard doesn't respond. My code looks the same as the guy in the tutorial video, and I don't know why my code doesn't work. I believe it's my wn.listen() method, but I'm not sure. Any help or suggestions would be greatly appreciated.

import turtle

wn = turtle.Screen()
wn.title("Pong by @TokyoEdTech")
wn.bgcolor("black")
wn.setup(width=800, height=600)
wn.tracer(0)

# Paddle A

paddle_a = turtle.Turtle()
paddle_a.speed(0)
paddle_a.shape("square")
paddle_a.color("white")
paddle_a.shapesize(stretch_wid=5, stretch_len=1)
paddle_a.penup()
paddle_a.goto(-350, 0)

# Paddle B
paddle_a = turtle.Turtle()
paddle_a.speed(0)
paddle_a.shape("square")
paddle_a.color("white")
paddle_a.shapesize(stretch_wid=5, stretch_len=1)
paddle_a.penup()
paddle_a.goto(350, 0)

# Ball
ball = turtle.Turtle()
ball.speed(0)
ball.shape("square")
ball.color("white")
ball.penup()
ball.goto(0, 0)


# Function
def paddle_a_up():
    y = paddle_a.ycor()
    y += 20
    paddle_a.sety(y)


# Keyboard binding
wn.listen()
wn.onkeypress(paddle_a_up(), "w")  # this calls the function paddle_a_up()

# Main game loop
while True:
    wn.update()