# Python NumPy For Your Grandma | Section 3.2 | newaxis

# Course Contents

- Introduction
- NumPy Arrays

2.1 What’s A NumPy Array

2.2 Creating NumPy Arrays

2.3 Indexing And Modifying 1-D Arrays

2.4 Indexing And Modifying Multidimensional Arrays

2.5 Basic Math - Intermediate Array Stuff

3.1 Broadcasting

**3.2 newaxis**

3.3 reshape

3.4 boolean indexing

3.5 nan

3.6 infinity

3.7 random - Common Operations

4.1 where

4.2 Math Funcs

4.3 all and any

4.4 concatenate

4.5 Stacking

4.6 Sorting

4.7 unique - Challenges

This video covers the newaxis keyword for inserting a new axis into a numpy array to increase its dimensionality. newaxis is usually used to make arrays compatible for broadcasting.

## Code

```
import numpy as np
# make 1d arrays
A = np.array([3, 11, 4, 5])
B = np.array([5, 0, 3])
# Deduct each element of B from each element of A
A[np.newaxis, :] - B[:, np.newaxis]
# Same as above, using None
A[None, :] - B[:, None]
```

## Transcript

Sometimes you may want to increase the dimensionality of an array by giving it a new axis. For example, suppose you have the following 1d arrays.

If you wanted to deduct each element of B from each element of A, you’d need to make the arrays compatible for subtraction. If A was a 1x4 array and B was a 3x1 array, A minus B would broadcast to your desired result. Surprise: you can use np.newaxis to promote the dimensionality of A and B for tasks like these. To use it, just put np.newaxis in the square bracket notation where ever you want to add a new axis.

For example, “A square bracket new axis comma colon” inserts a new axis in front of A’s existing axis, turning A into a 1x4 array and “B colon comma new axis” inserts a new axis behind B’s existing axis, turning B into a 3x1 array.

Note that newaxis is just an alias for the keyword None, so you’ll often see people using the None keyword here.