PQ_and_RS_are_Parallel.py

'''Write a Python Program to test whether two lines PQ and RS are parallel. The four points are P(x1,y1), 
Q(x2,y2), R(x3,y3), S(x4,y4).'''

print("Input x1,y1,x2,y2,x3,y3,x4,y4: ")
x1,y1,x2,y2,x3,y3,x4,y4 = map(float, input().split())
print("PQ and RS are parallel." if abs((x2 - x1)*(y4 - y3) - (x4 - x3)*(y2 - y1)) < 1e-10 else "PQ and RS are not parallel")