Collection in Python

Collections is a built-in module in Python, and it is a type of container that contains different modules like Counter, deque, UserDict, UserList etc. Some built-in containers are List, Tuple, Dictionary.

Syntax

import collections from Module_name

Counter

Counter is a function in the collections module. It is a subclass of the dictionary object and counts the number of elements, returning them in the form of an unordered dictionary. Here, the key specifies the element of the sequence, and the value represents the number of occurrences of that element in the sequence.

Syntax

from collections import Counter
dict_var = Counter(sequence)
#---------or--------------
import collections
var_dict = collections.Counter(sequence)

Example

import collections
sequence = ['a', 'b', 'a', 'b', 'a', 'b', 'a', 'b']
var_dict = collections.Counter(sequence)
print(var_dict)

Output

Counter({'a': 4, 'b': 4})

Example with from

from collections import Counter
sequence = ['a', 'b', 'a', 'b', 'a', 'b', 'a', 'b']
var_dict = Counter(sequence)
print(var_dict)

Output

Counter({'a': 4, 'b': 4})

Accessing the keys and values of dictionary

We can access the keys and values of the unordered dictionary.

from collections import Counter
sequence = ['a', 'b', 'a', 'b', 'a', 'b', 'a', 'b']
var_dict = Counter(sequence)
print("Keys:", var_dict.keys())
print("values:", var_dict['a'])

Output

Keys: dict_keys(['a', 'b'])
values: 4

elements() function

elements() function returns a list of all the elements in the Counter object.

from collections import Counter
sequence = ['a', 'b', 'a', 'b', 'a', 'b', 'a', 'b']
var_dict = Counter(sequence)
print("Elements are:", list(var_dict.elements()))

Output

Elements are: ['a', 'a', 'a', 'a', 'b', 'b', 'b', 'b']