Course 1 week 2 exercise 5: name 'np' is not defined

I don’t understand what the error means. np should be well defined at the first begining.
Please help

NameError Traceback (most recent call last)
in
----> 1 w = np.array([[1.], [2]])
2 b = 1.5
3 X = np.array([[1., -2., -1.], [3., 0.5, -3.2]])
4 Y = np.array([[1, 1, 0]])
5 grads, cost = propagate(w, b, X, Y)

NameError: name ‘np’ is not defined

Please run the cell containing import numpy as np before solving exercise 5.

issue solved. Thanks.

This is one of the things covered on the DLS FAQ Thread, which is worth a look on general principles even though you have the answer to this specific question from Balaji.