Python/ Calculate angle between 2 lines given their coords.

""" Calculate the angle between two lines that join at (x1, y1) """

from math import atan2, pi

def calculate_angle(x1,y1,x2,y2,x3,y3,x4,y4):
    # Calculate the angles created.
    delta_x = float(x2 - x1)
    delta_y = float(y2 - y1)
    answer = atan2(delta_y, delta_x)*180.0/pi

    delta_x = float(x4 - x3)
    delta_y = float(y4 - y3)
    answer1 = atan2(delta_y, delta_x)*180.0/pi

    # Get the answer
    if answer > answer1:
        return answer-answer1
    else:
        return answer1-answer


# Input stuff
print "Input coordinates for the first line"
print "------------------------------------"
x1 = float(raw_input('Enter x1 coord >'))
y1 = float(raw_input('Enter y1 coord >'))
x2 = float(raw_input('Enter x2 coord >'))
y2 = float(raw_input('Enter y2 coord >'))
print ""
print "Input coordinates for the second line"
print "Lets assume the node for the two lines is at (x1,y1)"
print "------------------------------------"
x3, y3 = x1 ,y1
print "x3 =",x1
print "y3 =",y1
x4 = float(raw_input('Enter x4 coord >'))
y4 = float(raw_input('Enter y4 coord >'))

result = calculate_angle(x1,y1,x2,y2,x3,y3,x4,y4)
print "The angle between the two joined lines is",result