difference between find() and index in python

stackoverflow.com › questions › 22190064 › difference-between-find-and-index

str.find returns -1 when it does not find the substring.

>>> line = 'hi, this is ABC oh my god!!'
>>> line.find('?')
-1

While str.index raises ValueError:

>>> line.index('?')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: substring not found

Both the functions behave the same way if a sub-string is found.

Answer from falsetru on Stack Overflow

GeeksforGeeks

geeksforgeeks.org › python › difference-between-find-and-index-in-python

Difference Between find() and index() in Python - GeeksforGeeks

July 23, 2025 - 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.

reddit.com › r/learnpython › why use index over find?

r/learnpython on Reddit: Why use index over find?

March 4, 2025 -

Won't index just make your code not work if it doesn't contain something while find still returns something so you can know if whatever you're looking for isn't in the thing?

Top answer

1 of 3

146

str.find returns -1 when it does not find the substring.

>>> line = 'hi, this is ABC oh my god!!'
>>> line.find('?')
-1

While str.index raises ValueError:

>>> line.index('?')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: substring not found

Both the functions behave the same way if a sub-string is found.

2 of 3

Also find is only available for strings where as index is available for lists, tuples and strings

>>> somelist
['Ok', "let's", 'try', 'this', 'out']
>>> type(somelist)
<class 'list'>

>>> somelist.index("try")
2

>>> somelist.find("try")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'list' object has no attribute 'find'

>>> sometuple
('Ok', "let's", 'try', 'this', 'out')
>>> type(sometuple)
<class 'tuple'>

>>> sometuple.index("try")
2

>>> sometuple.find("try")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'tuple' object has no attribute 'find'

>>> somelist2
"Ok let's try this"
>>> type(somelist2)
<class 'str'>

>>> somelist2.index("try")
9
>>> somelist2.find("try")
9

>>> somelist2.find("t")
5
>>> somelist2.index("t")
5

Just Academy

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Difference Between Find And Index In Python by Roshan Chaturvedi | JustAcademy

April 9, 2024 - The key difference between the two is how they handle scenarios where the substring is not found. The `find()` method returns -1 if the substring is not found, whereas the `index()` method raises a ValueError exception.

CodeSpeedy

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Difference between find() and index() in Python - CodeSpeedy

July 15, 2020 - Just like find(), index() method determines the position at which a substring is first found in a string. In the same way index() takes 3 parameters: substring that is to be searched, index of start and index of the end(The substring is searched between the start and end indexes of the string) out of which indexes of start and end are optional.

Medium

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Understanding the Difference Between find() and index() in Python | by Allwin Raju | Medium

December 21, 2024 - Understanding the Difference Between find() and index() in Python When working with strings in Python, locating a substring is a common task. Python provides two built-in methods to achieve this …

Quora

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What is the difference between index and find in Python? - Quora

Answer (1 of 2): index() is the method used in list which returns the lowest index in list that obj appears. If not found it will raise an exception indicating that value does not find. [code]aList = [123, 56.88, 'Python', True] print(aList.index(56.88)) [/code]prints 1 [code]print(aList.index(...

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Educative

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What is the difference between String find() and index() method?

Python provides the following two built-in methods to find the first occurrence of a given substring in a string: ... Both methods have the same syntax. However, in the case where the required substring is not found in the target string, there is a significant difference in the output of both ...

Just Academy

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Difference Between Find And Index In Python

The key difference between the two is how they handle scenarios where the substring is not found. The `find()` method returns -1 if the substring is not found, whereas the `index()` method raises a ValueError exception.

Talkerscode

talkerscode.com › howto › difference-between-find-and-index-in-python.php

Difference Between Find And Index In Python

We then use the find() method to check if the substring is present in the string. The find() method will return -1 if the substring is not present in the string. We then use the index() method to check if the substring is present in the string.

Plain English

python.plainenglish.io › pythons-find-and-index-functions-a-comprehensive-guide-c7dba18cc59d

Python’s find() and index() Functions: A Comprehensive Guide | by Durgesh Samariya | Python in Plain English

September 20, 2023 - The find() function is used to locate the first occurrence of a substring within a given string. It returns the index of the first character of the first occurrence of the substring. If the substring is not found, it returns -1. ... New Python ...

Stack Overflow

stackoverflow.com › questions › 20410385 › python-why-do-the-find-and-index-methods-work-differently

Python - Why do the find and index methods work differently? - Stack Overflow

Top answer

1 of 1

This has always been annoying ;-) Contrary to one answer, there's nothing special about -1 with respect to strings; e.g.,

>>> "abc"[-1]
'c'
>>> [2, 3, 42][-1]
42

The problem with find() in practice is that -1 is in fact not special as an index. So code using find() is prone to surprises when the thing being searched for is not found - it was noted even before Python 1.0.0 was released that such code often went on to do a wrong thing.

No such surprises occur when index() is used instead - an exception can't be ignored silently. But setting up try/except for such a simple operation is not only annoying, it adds major overhead (extra time) for what "should be" a fast operation. Because of that, string.find() was added in Python 0.9.9 (before then, only string.index() could be used).

So we have both, and that persists even into Python 3. Pick your poison :-)

CSEstack

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Difference between index() and find() in Python

July 9, 2020 - Note: The index() method can also be used to search the element in the Python list. ... We will use the same string and sub-string for find() method. samp_str = "CSEstack programmer" print(samp_str.find('stack')) ... You will find the same output result. Is there any difference between index() and find()?

TheLinuxCode

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Difference Between find() and index() in Python (Practical Patterns, Pitfalls, and 2026-Style Error Handling) – TheLinuxCode

February 1, 2026 - If you remember only one thing, remember this: find() makes failure easy to ignore; index() makes failure hard to ignore. The most expensive bugs here aren’t about forgetting the difference between -1 and ValueError. The expensive bugs happen when someone checks the returned integer in a way that doesn’t match how integers behave in Python.

Iditect

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Difference Between find( ) and index( ) in Python

s = "hello" result = s.index("l") ... not found in string.") # This block will be executed ... Use find() if you want a simple way to check for the presence of a substring in a string and don't want to handle exceptions....

Sololearn

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What is the difference Between find( ) and index( ) in Python? | Sololearn: Learn to code for FREE!

Quoted from https://www.w3schools.com/JUMP_LINK__&&__python__&&__JUMP_LINK/ref_string_find.asp "The find() method is almost the same as the index() method, the only difference is that the index() method raises an exception if the value is not found."

TheLinuxCode

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Difference Between find() and index() in Python – TheLinuxCode

January 27, 2026 - This is not a replacement for find() or index(), but it’s a good option when you want a single split and a clear indicator of presence. Both methods are implemented in optimized C and run in linear time relative to the length of the string. In practice, the difference between them is negligible for typical inputs.

w3reference

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Python: Why Do find() and index() Methods Behave Differently? Key Differences Explained — w3reference.com

Fails-Fast Behavior: index() raises an error immediately, which is useful when the substring must exist (e.g., parsing structured data like "YYYY-MM-DD" where "-" is expected). You need to check for the presence of a substring and handle its absence gracefully (without exceptions). Scenario: Searching for a keyword in user input. user_input = "I love Python programming" keyword = "Python" if user_input.find(keyword) != -1: print(f"Keyword '{keyword}' found!") else: print(f"Keyword '{keyword}' not found.")

Programiz

programiz.com › python-programming › methods › string › index

Python String index()

The only difference is that find() method returns -1 if the substring is not found, whereas index() throws an exception. ... Substring 'is fun': 19 Traceback (most recent call last): File "<string>", line 6, in result = sentence.index('Java') ValueError: substring not found · Note: Index in ...

All In The Diffrence

allinthedifference.com › difference-between-find-and-index-in-python

Understanding the Key Differences Between Find() and Index() in Python: A Comprehensive Guide

June 25, 2024 - It’s clear that choosing between these two depends largely on your specific needs: if you’re working with larger strings or repetitive tasks where misses might occur, find()’s non-interruptive nature is a godsend; but when certainty of matches is high and speed matters, nothing beats index(). Now armed with this knowledge about their efficiency differences, you’re well-prepared for coding more effective Python projects!