How can I count the occurrences of a list item

Question

Given an item, how to count its occurrences in a list in Python?

Answer 1

For Counting the occurrences there are many ways

1) Using count() 

For Example:
Categories = [12,34,45,56,67,12,12,34,45,56,56,45,56]
Categories.count(12)

Output

3

2) Counting all occurrences witjh count() method and using it either with or without dictionary

[[x,Categories.count(x)] for x in set(Categories)]  

Output:

[[34, 2], [67, 1], [12, 3], [45, 3], [56, 4]]

dict((x,Categories.count(x)) for x in set(Categories))

Output:

{34: 2, 67: 1, 12: 3, 45: 3, 56: 4}

The Output will be the same but the way it is been displayed is different.

3) Using Counter form collections library
from collections import Counter
Counter(Categories)

Output:

Counter({12: 3, 34: 2, 45: 3, 56: 4, 67: 1})

Hope this helps.