Find Last Occurrence of Substring in Python

In Python, working with strings is a common task in data processing and text analysis. The common operation is finding the last occurrence of a specific substring. It is useful in situations like extracting the domain names or locating the repeated elements in logs.

Python provides several methods to accomplish this; the most commonly used are ?

• Python rfind() Method
• Python rindex() Method

Using python rfind() Method

The Python rfind() method is used to find the last occurrence of the substring in the given string; if not found, it returns -1.

Syntax

string.rfind(value, start, end)

Example

Let's look at the following example, where we will consider the basic usage of the rfind().

str1 = "Welcome to tutorialspoint"
index = str1.rfind("t")
print("The last index of t in the given string is", index)

Output

The output of the above given example is:

The last index of t in the given string is 24

Uisng python rindex() Method

The Python rindex() method is used to find the last occurrence of a substring in a given string.

This method is similar to the rfind() method, but the difference is that the rfind() method returns -1, if the substring is not found, but the rindex() method raises an exception (Value Error).

Syntax

str.rindex(value, start, end)

Example 1

Consider the following example, where we are going to use the rindex() to find the last occurrence.

str1 = "Welcome to tutorialspoint"
index = str1.rindex('t')
print("The last index of t in the given string is",index)

Output

The output of the above example is as follows ?

The last index of t in the given string is 24

Example 2

In the following example, we are going to use rindex() and find the last occurrence of the substring that is not present in the original string and observe the output.

str1 = "Welcome to tutorialspoint"
index = str1.rindex('d')
print("The last index of t in the given string is",index)

Output

If we run the above program, it will generate the following output ?

Traceback (most recent call last):
  File "/home/cg/root/67f5acf8d76df/main.py", line 2, in <module>
index = str1.rindex('d')
            ^^^^^^^^^^^^^^^^
ValueError: substring not found