Saturday 13 June 2020

Lists in Python

Understanding Lists

Lists are the most versatile data structure used in Python. Lists store the data elements

sequentially and can be accessed by indexing. Indexing in lists start with “0” as the first index.

What’s make the Lists so powerful is, lists support different types of data types.

Lists are mutable, which means they can be modified after their creation unlike string.

 

Creating Lists in Python

A list in python is created by placing all the elements inside the square brackets [] with

comma separated.

list = [1, 2, “item”, 2.0]

list[2] = “mutable”                                 // lists are mutable and zero based index

print(list)                         

nested_list = [1, 2, [4, 5], 6]             // list stores list inside it.

print(nested_list)                      

Output:

[1, 2, “mutable”, 2.0]

[1, 2, [4, 5], 6]

Negative  Indexing in Lists

Unlike other data structures in other programming languages, Lists support negative

indexing which means, you can access the elements of list with negative indices too.

list = [1, 2, 3, 4, 5, 6]

print(list[-1])

print(list(-3))

Output:

6

4

Slicing Lists 

Slicing of list allows you to access the range of elements in the list.

Syntax:

list[start index : end index : gap]

it gives the elements starting from index “start index”  to one before “end index” with gap between indices.

By default, gap =1

list[1, 2, 3, 4, 5, 6]

print(list[1 : 4])

print(list[ :])

print(list[1 : 4 : 2])              // here gap = 2, means jump to index + 2 from index

Output:

[2, 3, 4]

[1, 2, 3, 4, 5, 6]

[2, 4]

 

 

8 comments:

  1. I want to create a list which enforce data type into it, so that it doesn't accept other data type values by mistake like array in other strictly types languages

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    Replies
    1. No,in Python's list you cannot restrict to store values of single type of data type and list is one of the primary data type in python that stores any type of data even simultaneously.

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