Numpy arithmetic

Question

I have the following code :

import numpy as np
x=np.array([[3, 5, 1]])
print(x.shape) #get (1,3)
np.multiply(x.shape, 8) #get [ 8, 24]

print(*x.shape) # get 1 3
np.array((np.multiply(*x.shape), 8)) #get [3, 8]

Please explain why/how np.multiply(*x.shape, 8) get [3, 8] ?

What are you trying to accomplish here? x,shape is just a tuple. Why multiply it? — hpaulj
– hpaulj, Commented Dec 1, 2018 at 17:36

sacuL · Accepted Answer · 2018-12-01 17:31:21Z

1

What is happening is that by doing

np.multiply(*x.shape)

You are unpacking the tuple (1,3) using the * operator, and passing each element as an argument to np.multiply. So that results in 1*3 which is 3.

Then, you are just wrapping the result of that up into an array with 8, so you end up with an array that is [3, 8]

answered Dec 1, 2018 at 17:31

sacuL

51.6k9 gold badges88 silver badges115 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

user8408080 · Accepted Answer · 2018-12-01 17:34:45Z

0

The * unpacks iterables. So if x.shape is (1,3) and you call np.multiply(*x.shape) you will actually call np.multiply(1,3) which gives 3. The 8 is just hardcoded, so nothing special there.

Also, because you wrote it: the 8 is not an argument of np.multiply here.

answered Dec 1, 2018 at 17:34

user8408080

2,4781 gold badge12 silver badges20 bronze badges

Collectives™ on Stack Overflow

Numpy arithmetic

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related