I keep getting an error saying that longPoints is being accessed before its assignment, and I can't seem to figure out what the problem is

Question

def main():
    delT = 0.25
    longest = 0
    shortest = 1000
    plt.ylim(-10, 10)
    plt.xlim(-10, 10)
    map = scipy.io.loadmat(\'cluster1.mat\')
    for i in