A substring is the part of a string. Python string provides various methods to create a substring, check if it contains a substring, index of substring etc. In this tutorial, we will look into various operations related to substrings.
Let’s first look at two different ways to create a substring.
We can create a substring using string slicing. We can use split() function to create a list of substrings based on specified delimiter.
s = 'My Name is Pankaj'
# create substring using slice
name = s[11:]
print(name)
# list of substrings using split
l1 = s.split()
print(l1)
Output:
Pankaj
['My', 'Name', 'is', 'Pankaj']
We can use in operator or find() function to check if substring is present in the string or not.
s = 'My Name is Pankaj'
if 'Name' in s:
print('Substring found')
if s.find('Name') != -1:
print('Substring found')
Note that find() function returns the index position of the substring if it’s found, otherwise it returns -1.
We can use count() function to find the number of occurrences of a substring in the string.
s = 'My Name is Pankaj'
print('Substring count =', s.count('a'))
s = 'This Is The Best Theorem'
print('Substring count =', s.count('Th'))
Output:
Substring count = 3
Substring count = 3
There is no built-in function to get the list of all the indexes for the substring. However, we can easily define one using find() function.
def find_all_indexes(input_str, substring):
l2 = []
length = len(input_str)
index = 0
while index < length:
i = input_str.find(substring, index)
if i == -1:
return l2
l2.append(i)
index = i + 1
return l2
s = 'This Is The Best Theorem'
print(find_all_indexes(s, 'Th'))
Output: [0, 8, 17]
You can checkout complete python script and more Python examples from our GitHub Repository.
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program executed,but the list is not printed
- nitin
Thanks for the examples and explanations, are great.
- Jorge