Methods vs functions in NumPy

Many things are implemented in NumPy as both functions and methods. For example, there is a np.sum function, that adds up all the elements:

import numpy as np

arr = np.array([1, 2, 0, 1])
np.sum(arr)

4

There is also a sum method of the numpy array object:

type(arr)

numpy.ndarray

arr.sum()

4

Nearly all the method versions do the same thing as the function versions. Examples are mean, min, max, sum, reshape. Choosing the method or the function will usually depend on which one is easier to read.