Python Container Datatypes

In the collections there are some container datatypes, which are alternatives to python’s general purpose built-in containers like dict, list, set etc.

Some of the containers are −

Sr.No. Container & Description
1 namedtuple()
Used to create tuple subclass with the name field
2 deque
Queue using list type data
3 Counter
Subclass of dict to count the hash-table objects
4 ChainMap
Used to create single view of multiple mappings
5 OrderedDict
Subclass of dict, where data are added in ordered manner
6 UserList
Wrapper for list to easier access.

To use this module, we should import it using −

import collections

Deque Object

The Deque is basically a generalization of stack and queue structure, where it is initialized from left to right. It uses the list object to create a deque.

Some Deque related methods are −

Sr.No. Methods & Description
1 append(x)
Add element x at the right side of the deque
2 appendleft(x)
Add element x at the left side of the deque
3 clear()
Clear the deque
4 count(x)
Count number of occurrences of x in the deque
5 index(x[, start[,stop]])
Return the position of x. If the start and stop are defined, it will find in that range
6 insert(i, x)
Insert x into the deque at position i
7 pop()
Remove and return element from the right side
8 popleft()
Remove and return element from the left side
9 reverse()
Reverse the contents of the deque
10 rotate(n = 1)
Rotate deque n times to the right

Example Code

 Live Demo

import collections as col
my_deque = col.deque('124dfre')
print(my_deque)
print("Popped Item: " + str(my_deque.pop()))
print("Popped Item From Left: " + str(my_deque.popleft()))
print(my_deque)

Output

deque(['1', '2', '4', 'd', 'f', 'r', 'e'])
Popped Item: e
Popped Item From Left: 1
deque(['2', '4', 'd', 'f', 'r'])

Counter Object

The counter is a subclass of a dict type object. It can be used to count the key values. The counters allow only integer value.

Some Counters related methods are −

Sr.No. Methods & Description
1 elements()
Return the elements, that much times the counter value holds.
2 most_common([n])
This method returns a list of most commonly used n elements from the counter. If n is not specified, it will return all.
3 subtract(iterable or mapping)
Subtract the counter value from two counter object, where keys are matched.
4 update(iterable or mapping)
It adds the values without replacing the values, where keys are matched.

Example Code

 Live Demo

import collections as col
text_list = ['ABC','PQR','ABC','ABC','PQR','Mno','xyz','PQR','ABC','xyz']
my_counter = col.Counter()
for element in text_list:
my_counter[element] += 1
print(my_counter)
print(my_counter.most_common(2))

Output

Counter({'ABC': 4, 'PQR': 3, 'xyz': 2, 'Mno': 1})
[('ABC', 4), ('PQR', 3)]

ChainMap Object

The ChainMap is used to encapsulates the dictionaries into single unit.

Some ChainMap members are −

Sr.No. Methods & Description
1 maps
It is used to return keys with its corresponding values.
2 new_child(m = None)
This method is used to insert a new dictionary at the first position of the chain.

Example Code

import collections as col
con_code1 = {'India' : 'IN', 'China' : 'CN'}
con_code2 = {'France' : 'FR', 'United Kingdom' : 'GB'}
code = {'Japan' : 'JP'}
chain = col.ChainMap(con_code1, con_code2)
print("Initial Chain: " + str(chain.maps))
chain = chain.new_child(code) #Insert New Child
print("Final Chain: " + str(chain.maps))

Output

Initial Chain: [{'India': 'IN', 'China': 'CN'}, {'France': 'FR', 'United Kingdom': 'GB'}]
Final Chain: [{'Japan': 'JP'}, {'India': 'IN', 'China': 'CN'}, {'France': 'FR', 'United Kingdom': 'GB'}]
Updated on: 2019-07-30T22:30:23+05:30

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