rindex() : Find the rightmost matching of the search string and return the position in Python

Find the rightmost matching of search string and return the position

main_string.rindex(search_string, start, end)

search_string

Required, String to be searched and position is returned if found.

start

Optional, Starting position of search , by default it is from 0 or starting position of string

end

Optional , ending position of search, by default it is end of the string.

This is case sensitive search

my_str='Welcome to plus2net.com Python section'
output=my_str.rindex('co') 
print(output) # output is 20

Using optional parameters start and end.

my_str='Welcome to plus2net.com Python section'
output=my_str.rindex('co',10,22)
print(output) # output is 20

If search string is not found then value error is generated.

my_str='Welcome to plus2net.com Python section'
output=my_str.rindex('co',10,21)
print(output)

Output

ValueError                        Traceback (most recent call last)
 in ()
      1 my_str='Welcome to plus2net.com Python section'
----> 2 output=my_str.rindex('co',10,21)
      3 print(output)

ValueError: substring not found

rindex() method raise an exception if searched string is not found but rfind() returns -1 if searched string is not found. That is the main difference between rindex() and rfind()

Example: Locating Last Occurrence of a Word

The `rindex()` method can be used to find the last occurrence of a word within a string, which is useful for parsing or analyzing text.

my_str = "Find the last apple in the apple orchard"
position = my_str.rindex("apple")
print("Last 'apple' found at index:", position)

Last 'apple' found at index: 27

Use Case: Extracting Text After the Last Delimiter

If we want to extract text after the last occurrence of a delimiter (e.g., a period or slash), `rindex()` can be extremely helpful.

file_path = "user/documents/reports/summary.pdf"
last_slash = file_path.rindex("/")
file_name = file_path[last_slash + 1:]
print("File name:", file_name)

File name: summary.pdf

Advanced Example: Using `rindex()` with Start and End Parameters

We can specify search limits using the start and end parameters to find occurrences within a defined range.

my_str = "error1: info; error2: critical; error3: debug"
position = my_str.rindex("error", 0, 20)
print("Last 'error' found in range:", position)

Last 'error' found in range: 14

Example: Handling `ValueError` Exception

The `rindex()` method raises a `ValueError` if the substring is not found. We can handle this using a try-except block.

try:
    position = "Hello World".rindex("Python")
    print("Position:", position)
except ValueError:
    print("Substring not found")

Output

Substring not found

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