In the formula, the numerator is the dot product of two vectors, and the denominator is the product of the norms of the two vectors.

Here is a simple way to write your formula:

import math

def dot_product(u, v):
  (x1, y1) = u
  (x2, y2) = v
  return x1 * x2 + y1 * y2

def norm(u):
  (x, y) = u
  return math.sqrt(x * x + y * y)

def get_angle(u, v):
  return math.acos( dot_product(u,v) / (norm(u) * norm(v)) )

def make_vector(p, q):
  (x1, y1) = p
  (x2, y2) = q
  return (x2 - x1, y2 - y1)

#first direction vector

#punt 1, PQ
#   [x,y]
P = (1,1)
Q = (5,3)

#punt 2, RS
R = (2,3)
S = (4,1)

angle = get_angle(make_vector(p,q), make_vector(r,s))

print(angle)

Because for complex numbers abs(number) will return magnitude of Complex Numbers.

Magnitude value will counted as : √x2+y2 = √(3² + 4²) = √(9 + 16) = √(25) = 5.0

So abs with complex number will return magnitude of complex numbers.

for further reference you can use https://www.geeksforgeeks.org/abs-in-python/.