I have no idea how to fix this error.

Maybe there's an open parenthesis or quotation mark somewhere before this line?

What is wrong with this code?

Class Ribbon: # I got an error on this line!
def __init__(self, xpos, ypos, m, g):self.x=xposself.y=yposself.mass=mself.gravity=g..def update(self, xpos, ypos):..def display(self, xpos, ypos):..

Here is your problem:

Class Ribbon (object): def __init__(self, xpos, ypos, m, g):self.x=xposself.y=yposself.mass=mself.gravity=g

also remember that other def must be indented properly as well