Difference Between find() and index() in Python Last Updated : 21 Nov, 2024 Comments Improve Suggest changes Like Article Like Report Both methods are used to locate the position of a substring within a string but the major difference between find() and index() methods in Python is how they handle cases when the substring is not found. The find() method returns -1 in such cases, while index() method raises a ValueError.Example of find() Python s = "hello world" # Finds the position of the substring "world" print(s.find("world")) # Returns -1 when substring is not found print(s.find("python")) # Finds the position of "o" starting from index 5 print(s.find("o", 5)) Output6 -1 7 Explanation:s.find("world") returns 6 because the substring "world" starts at index 6.s.find("python") returns -1 as substring "python" is not present in string.s.find("o", 5) starts the search from index 5 and finds the first occurrence of "o" at index 7.Example of index() Python s = "hello world" # Finds position of the substring "world" print(s.index("world")) # Raises a ValueError when substring is not found print(s.index("python")) # Finds position of "o" starting from index 5 print(s.index("o", 5)) 6 ERROR! Traceback (most recent call last): File "<main.py>", line 7, in <module> ValueError: substring not foundExplanation:s.index("world") returns 6 because substring "world" starts at index 6.When s.index("python") is executed then it raises a ValueError as the substring "python" is not in string.s.index("o", 5) starts searching from index 5 and finds the first occurrence of "o" at index 7.When to use find() and index()? Use find() when we need to check if a substring exists and do not want to handle exceptions.Use index() when we are sure that the substring exists or we want an exception to be raised if it doesn't exist. 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