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Python String find() Method

How to use Python's find() method to locate substrings and return their starting index, with optional start/end parameters for substring searches.

The String find() method searches for the first occurrence of the given string and returns its index. If specified string is not found, it returns -1.

The optional arguments start and end can be used to limit the search to a particular substring of the string.

Syntax

my_string.find(sub, start, end)

find() Parameters

Python String find() method parameters:

Parameter Condition Description
sub Required Any string you want to search for
start Optional An index specifying where to start the search. Default value is 0.
end Optional An index specifying where to stop the search. Default is the end of the string.

find() Return Value

Python String find() method returns an integer value:

  • If the substring exists inside the string, it returns the index of the first occurrence of the substring.
  • If a substring does not exist inside the string, it returns -1.

Examples

Example 1: Find if a given String is contained in a String

If the given string is contained in the string, then find() method returns the index of the first occurrence:

my_str = 'Tom is a Developer on tutorialreference.com Development Team'
result = my_str.find('Dev')
print(result) # Output: 9

output

9

If the given string is not found in the string, then find() method returns -1.

my_str = 'Tom is a Developer on tutorialreference.com Development Team'
result = my_str.find('Ryan')
print(result) # Output: -1

output

-1

Example 2: Find if a given String is contained in a String with start and end indexes

If you want to limit the search to a substring of the given string, you can specify the start parameter and/or the end parameter.

my_str = 'Tom is a Developer on tutorialreference.com Development Team'
sub = "Dev"

result = my_str.find(sub)       
print(result) # Output: 9

result = my_str.find(sub, 4)
print(result) # Output: 9

result = my_str.find(sub, 4, 6) 
print(result) # Output: -1

output

9
9
-1

Example 3: Check if a given String exists in a String

The find() method can be used to check if a given string is contained in a string: just check the returned integer.

my_str = "Python is powerful."
sub = "Python"
if my_str.find(sub) != -1:
    print(f"The substring '{sub}' exists in the text.")
else:
    print("The substring does not exist in the text.")

output

The substring 'Python' exists in the text.

However, it is not meant to be used in this way! To check if sub is a substring or not, use the in operator.

find() method vs index() method

The find() method is identical to the index() method.

The only difference is that the index() method raises a ValueError exception, if the substring is not found.

An example to compare find() and index():

my_str = 'Tom is a Developer at ABC'
result = my_str.find('Manager')
print(result) # Output: -1

my_str = 'Tom is a Developer at ABC'
result = my_str.index('Manager') # Triggers ValueError: substring not found

output

-1
Traceback (most recent call last):
  File "main.py", line 6, in <module>
    result = my_str.index('Manager')
ValueError: substring not found
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