Cross product of two vectors in Python

are you asking about the formula for the cross product? Or how to do indexing and lists in python?

The basic idea is that you access the elements of a and b as a[0], a[1], a[2], etc. (for x, y, z) and that you create a new list with [element_0, element_1, ...]. We can also wrap it in a function.

On the vector side, the cross product is the antisymmetric product of the elements, which also has a nice geometrical interpretation.

Anyway, it would be better to give you hints and let you figure it out, but that's not really the SO way, so...

def cross(a, b):
    c = [a[1]*b[2] - a[2]*b[1],
         a[2]*b[0] - a[0]*b[2],
         a[0]*b[1] - a[1]*b[0]]

    return c

import numpy as np
a = np.array([1,0,0])  
b = np.array([0,1,0])  
#print the result    
print(np.cross(a,b))

If you want to implement the cross product yourself you may see http://en.wikipedia.org/wiki/Vector_cross_product or a math/physics book. Shortly (a1, a2, a3) X (b1, b2, b3) = (a2*b3-a3*b2, a3*b1-a1*b3, a1*b2-a2*b1)

I defined a successror funtion z,This is to help write the formulas of the cross product In a slightly consise way.here is the code

    from numpy import zeros
    def z(a):
      if a == 0 or a == 1:
       return a+1
      elif a == 2:
       return 0
    n = 3
    i = 0
    v = zeros(n, float)
    v1 = zeros(n, float)
    v2 = zeros(n, float)
    v1[0] = float(input("enter x component of v1 "))
    v1[1] = float(input("enter y component of v1 "))
    v1[2] = float(input("enter z component of v1 "))
    v2[0] = float(input("enter x component of v2 "))
    v2[1] = float(input("enter y component of v2 "))
    v2[2] = float(input("enter z component of v2 "))


    def cp(x, y):
     global i
     while i < n:
      v[i] = x[z(i)]*y[z(z(i))]-x[z(z(i))]*y[z(i)]
      i = i + 1
     return v


    ans = cp(v1, v2)
    print(ans)