Numpy is a package for scientific computing in Python.

## Vector arithmetic

Declaration

a = np.array([1,2,3,4]) [1 2 3 4]

Addition / Subtraction

a = np.array([1,2,3,4]) b = np.array([4,3,2,1]) a + b array([5, 5, 5, 5]) a - b array([-3, -1, 1, 3])

Scalar Multiplication

a = np.array([1,2,3,4]) a * 3 array([ 3, 6, 9, 12])

To see why it is charming to use numpy’s array for this operation You have to consider the alternative:

c = [1,2,3,4] d = [x * 3 for x in c]

Dot Product

a = np.array([1,2,3,4]) b = np.array([4,3,2,1]) a.dot(b) 20 # 1*3 + 2*3 + 3*2 + 4*1

Stay tuned for more algebraic stuff with numpy!