Master Python's String.find() Method: Syntax, Examples & Alternatives

What is Python String.find()?

The String.find() method in Python returns the index of the first occurrence of a specified substring within a string. If the substring isn’t found, it gracefully returns -1 instead of raising an exception, making it a convenient choice for substring searches.

In this guide, you’ll learn how to use find() effectively, explore its parameters, compare it with related methods, and even count how many times a substring appears.

• Understanding String.find()
• Syntax and parameters
• Using default arguments
• Specifying a start index
• Defining a start and end range
• Finding positions of substrings
• Comparing with rfind()
• Comparing with index()
• Counting substring occurrences

Syntax of Python string find()

The method’s signature is straightforward:

string.find(substring, start, end)

Parameters

• substring – The text you’re searching for.
• start (optional) – Index where the search begins; defaults to 0.
• end (optional) – Index where the search ends; defaults to the string’s length.

Using find() with Default Values

When no start or end is provided, find() scans the entire string from the beginning. It returns the index of the first match or -1 if none is found.

Example:

mystring = "Meet Guru99 Tutorials Site.Best site for Python Tutorials!"
print("The position of Tutorials is at:", mystring.find("Tutorials"))

Output:

The position of Tutorials is at: 12

Specifying a Start Index

Providing a start argument limits the search to begin at that position, extending to the string’s end.

Example:

mystring = "Meet Guru99 Tutorials Site.Best site for Python Tutorials!"
print("The position of Tutorials is at:", mystring.find("Tutorials", 20))

Output:

The position of Tutorials is at 48

Defining a Start and End Range

By supplying both start and end, you can confine the search to a specific slice of the string.

Example:

mystring = "Meet Guru99 Tutorials Site.Best site for Python Tutorials!"
print("The position of Tutorials is at:", mystring.find("Tutorials", 5, 30))

Output:

The position of Tutorials is at 12

Finding Positions and Handling Missing Substrings

Here’s how find() behaves when the substring is present and when it’s absent.

Example:

mystring = "Meet Guru99 Tutorials Site.Best site for Python Tutorials!"
print("The position of Best site is at:", mystring.find("Best site", 5, 40))
print("The position of Guru99 is at:", mystring.find("Guru99", 20))

Output:

The position of Best site is at: 27
The position of Guru99 is at: -1

Comparing with rfind()

rfind() is similar to find() but returns the highest index where the substring occurs. If the substring isn’t present, both methods return -1.

Example:

mystring = "Meet Guru99 Tutorials Site.Best site for Python Tutorials!"
print("The position of Tutorials using find() : ", mystring.find("Tutorials"))
print("The position of Tutorials using rfind() : ", mystring.rfind("Tutorials"))

Output:

The position of Tutorials using find() :  12
The position of Tutorials using rfind() :  48

Comparing with index()

The index() method behaves like find() but raises a ValueError when the substring is missing.

Example:

mystring = "Meet Guru99 Tutorials Site.Best site for Python Tutorials!"
print("The position of Tutorials using find() : ", mystring.find("Tutorials"))
print("The position of Tutorials using index() : ", mystring.index("Tutorials"))

Output:

The position of Tutorials using find() :  12
The position of Tutorials using index() :  12

When the substring isn’t found:

mystring = "Meet Guru99 Tutorials Site.Best site for Python Tutorials!"
print("The position of Tutorials using find() : ", mystring.find("test"))
print("The position of Tutorials using index() : ", mystring.index("test"))

Output:

The position of Tutorials using find() :  -1
Traceback (most recent call last):
  File "task1.py", line 3, in <module>
    print("The position of Tutorials using index() : ", mystring.index("test"))
ValueError: substring not found

Counting Substring Occurrences

To tally how many times a substring appears, iterate through the string and repeatedly call find() with an updated start index.

Example:

my_string = "test string test, test string testing, test string test string"
startIndex = 0
count = 0
for _ in range(len(my_string)):
    k = my_string.find('test', startIndex)
    if k != -1:
        startIndex = k + 1
        count += 1
print("The total count of substring test is:", count)

Output:

The total count of substring test is:  6

Key Takeaways

• find() returns the first matching index or -1 if absent.
• Parameters: substring, optional start (default 0), optional end (default string length).
• Use start to begin the search at a specific position.
• Use start and end to limit the search to a substring slice.
• rfind() returns the last matching index.
• index() is stricter, raising an error when the substring is missing.
• Looping with find() can count total occurrences.