SubString In Python

We know that a string is a sequence of characters, but today we will learn how to get a part of any string, known as substring.

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String Slicing

String slicing can be done using the [] (square brackets) notation, just as you get index.

The string[index] will return a single character of your string at the index.Since the indexing starts at 0, the string[0] will give you the very first character and the string[-1] will give the very last character.And the rest of the characters can be found using their position

my_string = ‘Get a complete Python tutorial at FITA’   print(my_string[0])   print(my_string[len(my_string)//2])   print(my_string[-1])

And the above code will output..

G o A

You can get the training even if you are not in GOA. The string[first_index:] will give you all the characters starting from the index given.

print(my_string[6:]) print(my_string[6::])

This will give give you all the characters except for the first 6,both the lines will give you the same output as

complete Python tutorial At FITA

The string[:end_index] will give all the characters until the given index.

my_string =’Get a complete Python tutorial At FITA’   print(my_string[:6])

This will give you the first 6 characters of the my_string.

Get a

The string[::step] will give all the characters with a step or skip of the the value For example

my_string =’Get a complete Python tutorial At FITA’   print(my_string[::11])

This will give you characters starting from 0 till the end but with a skip of 11 characters in between.Here is the output..

Get

Note that this is not the first 3 characters, let me give another example

print(my_string[::25])

Output

Go

Now let’s fill all the gaps with a start ,end, step. The my_string[start:end:step] will give you the characters from starting position to the end position with a skip of step characters.

my_string =’Get a complete Python tutorial At FITA’   print(my_string[4:35:12]) print(my_string[9::4]) print(my_string[:24:10]) print(my_string[9:18:4])

Here is the output for the above

aya pet ol A Gln pet

A negative index will mean that you start from the end i.e., from right to left.

print(my_string[-2]) # T

will give the last second character.

print(my_string[-6:]) # t FITA

will give last 6 characters

print(my_string[6:-6]) # complete Python tutorial

Will give all characters except the first 6 and last 6 characters.

find() method

The find() is a built-in method in python which will return the starting index of the substring in the string, else return -1 if it’s not present. For instance,

s = ‘Get a complete Python tutorial At FITA’   print(s.find(‘FITA’))

Will give you 34.

Check for a substring

You can also use the in or not in keywords to check if a substring is present in the string, which will give a boolean result.

my_string = ‘Get a complete Python tutorial At FITA’   print(‘ATUFA’ not in my_string) print(‘complete’ in my_string)

Which outputs..

True True

Also you can count the number of occurrences of the substring , when you have checked if it is present, else it will return 0.

my_string = ‘Get a complete Python tutorial At FITA’   print(my_string.count(‘FIT’)) print(my_string.count(‘a’))

Output

1 4

Splitting Strings

You can split a string at a particular substring and simultaneously create a list of all the remaining substrings excluding split substring using the .split() method. Here’s an example of the split method.

my_string = ‘Get a complete Python tutorial At FITA’   print(my_string.split(‘ ‘)) print(my_string.split(‘P’))

In the first print statement I am splitting at space, and in the second one at P. Here’s the output

[‘Get’, ‘a’, ‘complete’, ‘Python’, ‘tutorial’, ‘At’, ‘FITA’] [‘Get a complete ‘, ‘ython tutorial At FITA’]