Working with Python - Slicing the List

Introduction

In this blog post we are trying to discuss about Python List concept and how to Slicing the List.

Hope it will be interesting.


Characteristic of List

Here are some common characteristic of List

·         Values are ordered

·         Mutable

·         A list can hold any number of values

·         Value can have any data type

·         A list can add, remove, and alter the values

 

 

How to Create List

# Creating a Empty List

list=[]

#Creating List with ValueError

list=['Joydeep','Mayuree','Surrya']

print(list)

à['Joydeep', 'Mayuree', 'Surrya']

 

Assign a List Value to Variable

list=['Joydeep','Mayuree','Surrya']

name1=list[0]

name2=list[1]

print(name1)

print(name2)

àJoydeep

àMayuree

 

Slicing the List

Before moving the Slicing Section we have to understand the Indexing of List.

We have a list of Character

 

list=['J','O','Y','D','E','E','P']

 


 

We have two type of Indexing with List.

First one is Forward Indexing and second one is Backward Indexing.

The forward indexing starts from 0 and backward indexing starts from -1

 

Stepping Forward

Take a simple example:

From the above List, we are going to print from position 0 to 3 forward.

 

list=['J','O','Y','D','E','E','P']

print(list[0:3])

à['J', 'O', 'Y']

 

You are going to think why it is not going to print ‘J’,’O’,’Y’,’D’.

The formula is From [Start Position] to [Last Position – 1]

 

Now try this

list=['J','O','Y','D','E','E','P']

print(list[:3])

à['J', 'O', 'Y']

 

Here in this example, we are not providing any Start Point, so it by default 0

 

Now we have to understand the Jumping within the List

list=['J','O','Y','D','E','E','P']

print(list[:7:2])

à['J', 'Y', 'E', 'P']

 

The formula is LIST[Start Position], [Last Position] – 1, [Step])

 

Stepping Backward

 

The formula is From [Start Position] to [Last Position + 1]

 

list=['J','O','Y','D','E','E','P']

print(list[-1:-3:-1])

à ['P', 'E']

 

Let’s understand this example.

The First position is -1. So it prints ‘P’

The Last position is -3. But according to formula (-3 + 1) = -2. So it’s going to print ‘E’

 

One thing we have to remember, if the Step is Positive or Not Define, it’s a forward movement List and the Step is Negative, it’s a backward movement List.

 

 

Hope you like it.

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