Collection Module

The Python collection module is defined as a container that is used to store collections of data, for example, list, dict, set, and tuple, etc. It was introduced to improve the functionalities of the built-in collection containers.

Python collection module was first introduced in its 2.4 release.

There are different types of collection modules which are as follows:

namedtuple()

The python namedtuple() function returns a tuple-like object with names for each position in the tuple. It was used to eliminate the problem of remembering the index of each field of a tuple object in ordinary tuples.

Examples

snippet
pranshu = ('Pranshu', 24, 'M')
print(pranshu)

Output:

Output
('Pranshu', 24, 'M')

OrderedDict()

The Python OrderedDict() is similar to a dictionary object where keys maintain the order of insertion. If we try to insert key again, the previous value will be overwritten for that key.

Example

snippet
import collections
d1=collections.OrderedDict()
d1['A']=10
d1['C']=12
d1['B']=11
d1['D']=13

for k,v in d1.items():
    print (k,v)

Output:

Output
A 10 C 12 B 11 D 13

defaultdict()

The Python defaultdict() is defined as a dictionary-like object. It is a subclass of the built-in dict class. It provides all methods provided by dictionary but takes the first argument as a default data type.

Example

snippet
from collections import defaultdict  
number = defaultdict(int)  
number['one'] = 1  
number['two'] = 2  
print(number['three'])

Output:

Output
0

Counter()

The Python Counter is a subclass of dictionary object which helps to count hashable objects.

Example

snippet
from collections import Counter  
c = Counter()
list = [1,2,3,4,5,7,8,5,9,6,10]  
Counter(list)
Counter({1:5,2:4})  
list = [1,2,4,7,5,1,6,7,6,9,1]  
c = Counter(list)  
print(c[1])

Output:

Output
3

deque()

The Python deque() is a double-ended queue which allows us to add and remove elements from both the ends.

Example

snippet
from collections import deque
list = ["x","y","z"]
deq = deque(list)
print(deq)

Output:

Output
deque(['x', 'y', 'z'])
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