Count the number of occurences using Counter() in Python

Counter is an object of collections module, and it is a dict subclass for counting hashable objects, in Python 3.

To count the number of elements occurrences in a list

>>> from collections import Counter
>>> z = ['blue', 'red', 'blue', 'yellow', 'blue', 'red']
>>> Counter(z)
Counter({'blue': 3, 'red': 2, 'yellow': 1})

Count the number of alphabet occurrences in a text

>>> from collections import Counter
>>> Counter("This is a test")
Counter({' ': 3, 's': 3, 'i': 2, 't': 2, 'a': 1, 'e': 1, 'h': 1, 'T': 1})

To find the n most common words in a text

n is the number of most common words to find

Counter(the_text).most_common(3)

For more information, read The Python Standard Library