Filtering with Boolean Index

Getting some elements out of an existing array and creating a new array out of them is called filtering.

In NumPy, you filter an array using a boolean index list  An element is contained in the filtered array only if the value at an index is True. 

Use bitwise operator &, |, ~ for and, or, and not, respectively.

Using where for ndarray Comprehension

Using a list comprehension with if statement can be useful for filtering. While there is no ndarray comprehension, a similar task can be done using this method:

where(condition, x, y)
returns elements chosen from x or y depending on condition.

Making a Structured Array

Unlike list, NumPy can only work with 1 data type. We can force NumPy to work with multiple data types by assigning a dtype. The resulting array is called a structured array. 

Sorting ndarray

To sort ndarray, you can use:

np.sort(arr)
returns a sorted copy of an array.