Collections in Python 3 : Easy To Understand

In this post, we will discuss the built-in collections in python.

Let us first understand what do we mean by collections?

👉 Collections are nothing but containers used to store data. So basically, when we want to store any data collectively it can be achieved using collections.

Collections in Python

There are 4 types of built-in collections in python.

1. List
2. Tuple
3. Set
4. Dictionary

Let’s understand them in more detail.

List

In python, a list is a collection that is ordered and changeable. They are written with square [] brackets.

Example:

a = [1,2,3,4,5]
print(a)

Tuple

In python, a tuple is a collection that is ordered and unchangeable. They are written with round () brackets.

Example:

b = (1,2,3,4,5)
print(b)

Set

In python, a set is a collection that is unordered and unindexed. They are written with curly {} brackets.

The set will never contain a duplicate element.

Example:

c = {1,2,3,4,5}
print(c)

Dictionary

In python, a dictionary is a collection that is unordered, indexed, and changeable. They are written with curly {} brackets as a key-value pair.

Example:

d = {'a':1,'b':2,'c':3,'d':4,'e':5}
print(d)

Collection Module

The collections module provides alternatives to the above mentioned built-in container data types.

namedtuple()

The namedtuple() function returns a tuple-like object with named fields. These field attributes are accessible by index as well as by lookup.

import collections
employee = collections.namedtuple('employee', [name, department, salary])

#Creating new object
emp1 = employee("Dipendra", IT, 50000)

#Getting attribute value by index
emp1[0]  #this will give Dipendra

#Getting attribute value by lookup
emp1.salary  #this will give 50000

OrderedDict()

The OrderedDict() function is similar to a normal dictionary object in Python. However, it remembers the order of the keys in which they were first inserted.

import collections
d1 = collections.OrderedDict()
d1['A'] = 1
d1['C'] = 3
d1['B'] = 2
d1['D'] = 4

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

While reading and printing the collection the item would be returned in the order they were inserted.

A 1
C 3
B 2
D 4

deque()

A deque object support appends and pops from either end of a list

r = collections.deque([1,2,3,4,5])

Know more about collection modules in python.

Summary

Here is a quick summary of collections in python you have learned above.

I hope you got a basic understanding of using collections in python.

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You may check out our ASP.NET Core tutorial and various other posts on C# as well.

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