How to count occurrences of elements in an array

You can count occurrences of elements in an array with the following code. If you want to learn Python, I highly recommend reading This Book.

How to count occurrences of element in array — How to count occurrences of elements in an array

Method 1

import numpy as np
a = np.array([1, 2, 3, 4, 1, 1, 2, 1, 4, 4, 1])
print(np.count_nonzero(a == 1))
print(np.count_nonzero(a == 2))
print(np.count_nonzero(a == 3))
print(np.count_nonzero(a == 4))

Method 2

import numpy as np
b = np.array([1, 2, 3, 4, 1, 1, 2, 1, 4, 4, 1])
(unique, counts) = np.unique(b, return_counts=True)
print(unique, counts)

[1 2 3 4] [5 2 1 3]

Method 3

import collections, numpy
a = numpy.array([1, 2, 3, 4, 1, 1, 2, 1, 4, 4, 1])
print(collections.Counter(a))

Counter({1: 5, 4: 3, 2: 2, 3: 1})

Method 4

import numpy as np
a = np.array([1, 2, 3, 4, 1, 1, 2, 1, 4, 4, 1])
print((a == 1).sum())
print((a == 2).sum())
print((a == 3).sum())
print((a == 4).sum())