rashmi agar
66 posts
Mar 17, 2025
10:02 PM
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Python offers several built-in methods for string manipulation, and one of the lesser-known but powerful rindex python
. This method is particularly useful when you need to find the last occurrence of a substring in a given string. In this article, we will explore how rindex() works, its syntax, and how it differs from similar methods like rfind().
What is rindex()?
The rindex() method in Python is used to find the highest (rightmost) index of a specified substring in a given string. If the substring is found, it returns the index of its first character. However, if the substring does not exist within the string, it raises a ValueError.
Syntax
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string.rindex(substring, start, end)
substring: The string to search for.
start (optional): The starting index from which to begin the search.
end (optional): The ending index where the search stops.
Example Usage
Finding the Last Occurrence of a Substring
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text = "Python is fun, and Python is powerful."
index = text.rindex("Python")
print("Last occurrence of 'Python' is at index:", index)
Output:
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Last occurrence of 'Python' is at index: 18
Since the word "Python" appears twice in the string, rindex() returns the index of the last occurrence (18).
Handling ValueError Exception
If the substring is not found, Python raises a ValueError, which can be handled using a try-except block:
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try:
index = text.rindex("Java") # 'Java' is not in the text
print("Last occurrence is at:", index)
except ValueError:
print("Substring not found!")
Output:
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Substring not found!
Difference Between rindex() and rfind()
Both rindex() and rfind() locate the last occurrence of a substring. However, the key difference is:
rindex() raises an exception (ValueError) if the substring is not found.
rfind() returns -1 if the substring is not found, making it safer in some cases.
Example:
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print(text.rindex("Java")) # Raises ValueError
print(text.rfind("Java")) # Returns -1
Conclusion
The rindex() method is a powerful tool for locating substrings from the right side of a string. However, its exception-raising behavior makes it slightly less flexible than rfind(). Understanding when to use rindex() can help improve string handling efficiency in Python applications.
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