(self, y)
create a shelf. y is y-position of first block
create a shelf. y is y-position of first block
create a shelf . y is y - position of first block
def __init__(self, y):
        "create a shelf. y is y-position of first block"
        self.y = y
        self.x = -150
def __init__ ( self , y ) : self . y = y self . x = - 150