how to map the number of times an element appears in a list python code example

Example 1: count occurrences of value in array python

>>> l = ["a","b","b"]
>>> l.count("a")

Example 2: count occurrence in array python

arr = np.array( [1, 2, 3, 2, 1, 2])
occ = np.count_nonzero(arr==0)
print(occ)
0
occ = np.count_nonzero(arr==1)
print(occ)
2