As we read earlier about Python if else elif . Now we will study about Indexing and Slicing in Python. In python programming language, Now we will read the concepts further, all of them will use python indexing and slicing. so lets start.

What is Indexing in python ?

Indexing means referring to an element of an iterable by using its position within the iterable.

To retrieve an element of the list, we can use the index operator [ ] :

list_1 = [ 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h' ]

Python Indexing : Indexing from the start

[ 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h' ] 
   ↓    ↓    ↓    ↓    ↓    ↓    ↓    ↓ 
   0    1    2    3    4    5    6    7

Example :

list_1 = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h']
x = list_1[3]
print(x)

# or

list_1 = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h']
print(list_1[3])

Output :

d
d

Python Negative Indexing : Negative Indexing starts from the end

[ 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h' ]
   ↓    ↓    ↓    ↓    ↓    ↓    ↓    ↓ 
  -8   -7   -6   -5   -4   -3   -2   -1

Example :

list_1 = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h']
x = list_1[-4]
print(x)

# or

list_1 = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h']
print(list_1[-4])

Output :

e
e

What is Slicing in Python ?

Slicing is a technique by which we can get a sub – string using indexing is known as Slicing.

Python Slicing syntax :

Variable [ Start : End : Step ]

In the above syntax, the “Start” is the index of the first element and “End” is the index of the element to stop at without including it in the slice.

Example :

list_1 = [ 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h' ]
print(List_1[1:6])

Output :

[ 'b', 'c', 'd', 'e', 'f' ]

You can leave either slice boundary blank means start (or go to) the end of the list.

Example : 1

list_1 = [ 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h' ] 
print(list_1[3:])

Output : 1

[ 'd', 'e', 'f', 'g', 'h' ]

Example : 2

list_1 = [ 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h' ]
print(list_1[:5])

Output : 2

[ 'a', 'b', 'c', 'd', 'e' ]

To using a negative indexing, you will set the Start/Stop bounds relative to their position from the end of the list.

Example :

list_1 = [ 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h' ]
print(list_1[-6:-1])

Output :

['c', 'd', 'e', 'f', 'g']

A “for” loop works exactly the same way; the first example below has no output, but the second example does :

Example : 1

for i in range(-1, -6):
    print(i)

Output : 1

Example : 2

for i in range(-6, -1):
    print(i)

Output : 2

-6 
-5 
-4 
-3 
-2

Stepping in Python

In python, the slicing can take an third argument, which is sets the interval at which elements are included in the slicing is known as stepping.

Example : 1

list_1 = [ 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h' ] 
print(list_1[::3])

Output : 1

['a', 'd', 'g']

Example : 2

list_1 = [ 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h' ] 
print(list_1[1::3])

Output : 2

['b', 'e', 'h']

The negative step values reverse the direction of the original list.

Example :

list_2 = [ 'h', 'e', 'l', 'l', 'o' ] 
print(list_2[: : -1])

Output :

['o', 'l', 'l', 'e', 'h']

How to check the datatype in Python?

General syntax to check the data type :

Type(x)

For Integer

Example :

x = 24 
print(type(x))

Output :

<class 'int'>

For Float

Example :

x = 24.5 
print(type(x))

Output :

<class 'float'>

For Complex

Example :

x = 24j 
print(type(x))

Output :

<class 'complex'>

For String

Example :

x = 'Hello' 
print(type(x))

Output :

<class 'str'>

For List

Example :

x = [1,2,3] 
print(type(x))

Output :

<class 'list'>

For Tuple

Example :

x = (1,2,3) 
print(type(x))

Output :

<class 'tuple'>

For Dictionary

Example :

x = {'a':1, 'b':2, 'c':3} 
print(type(x))

Output :

<class 'dict'>

For Set

Example :

x = {1,2,3} 
print(type(x))

Output :

<class 'set'>

How to check the length in python ?

Length function is used to calculate total element of any collection or sequence or iterable data types.

General syntax :

len(iterable)

Length function always return Integer datatype.

Example :

x = 'Hello' 
print(len(x))

Output :

5

String is a immutable data type.

⇒ Immutable : We can’t modify content / values of immutable data type because original string is immutable. we can’t modify the original string.