Python find intersection of two vectors using matplotlib and numpy

vector_intersection.md

from numpy import dot,array,empty_like
from matplotlib.path import Path

def make_path(x1,y1,x2,y2):
    return Path([[x1,y1],[x1,y2],[x2,y2],[x2,y1]])

def perp( a ) :
    b = empty_like(a)
    b[0] = -a[1]
    b[1] = a[0]
    return b

# line segment a given by endpoints a1, a2
# line segment b given by endpoints b1, b2
# return 
def seg_intersect(a1,a2, b1,b2) :
    da = a2-a1
    db = b2-b1
    dp = a1-b1
    dap = perp(da)
    denom = dot( dap, db)
    num = dot( dap, dp )
   
    x3 = ((num / denom.astype(float))*db + b1)[0]
    y3 = ((num / denom.astype(float))*db + b1)[1]
    p1 = make_path(a1[0],a1[1],a2[0],a2[1])
    p2 = make_path(b1[0],b1[1],b2[0],b2[1])
    if p1.contains_point([x3,y3]) and p2.contains_point([x3,y3]):
        return x3,y3
    else:
        return False

p1 = array( [2.0, 1.0] )
p2 = array( [7.0, 3.0] )

p3 = array( [2.0, 5.0] )
p4 = array( [5.0, 2.0] )

print seg_intersect( p1,p2, p3,p4)