Python – Part #2 (Data Collections)

DATA COLLECTION

There are four built-in collections of data types in Python, each one with different qualities for particular purposes.

LISTS:

– Lists are used to store multiple items in a single variable and are created using square brackets [ ].

– List items can be ordered, they are changeable, allow duplicate values, and can contain any data type.

– List items are indexed, the first item has index [0], the second item has index [1], and so on.

– ” : ” colon is used inside the index as a range.

– To check the type of list we are using we write print (type(list_name))

Example #1:

numbers = [“1”, “2”, “3”]

print(numbers[0])

Output:

        >> 1

Example #2:

list1 = [“letter”, 1.4, True, False, “name”, 17]

print(list1[1:4])

Output:

        >> [1.4, True, False]

TUPLES:

Tuples are used to store multiple items in a single variable, however, they are a collection that is ordered and unchangeable.

As opposed to the list syntax, the tuples are written with round brackets ( ).

They can contain multiple data types as well.

Example #1:

numbers = (“1”, “2”, “3”)

print(numbers[2])

Output:

        >> 3

Example #2:

numbers = (“1”, “2”, “3”)

print(type(numbers))

        >> <class ‘tuple’>

SETS:

A set is a collection of data types that is unordered, unchangeable, unindexed, and duplication is not allowed.

A set uses curly brackets { }.

Example #1:

numbers = {“1”, “2”, “3”}

print(numbers[2])

Output:

        >> TypeError: ‘set’ object is not subscriptable     #Error due to unindexation.

Example #2:

numbers = {“1”, “2”, “3”}

print(numbers)

Output:

        >> {‘3’, ‘2’, ‘1’}

DICTIONARIES:

They are ordered, changeable, and do not accept duplicates.

Dictionaries are used to store data values in key : value pairs, and are written with curly brackets.

A visual example of key: value pairs:

Example #1: