Find Function in Python

Last Updated on June 30, 2023 by Mayank Dham

The find() function in Python is a built-in method that allows you to search for a substring within a larger string and retrieve its starting index. It provides a convenient way to locate specific patterns or sequences of characters within a string, enabling you to perform various operations like extracting data, validating inputs, or manipulating text.

In this article, we will explore the functionality and usage of the find() function in Python. We will delve into the syntax, parameters, and techniques to effectively employ this function in your code. By understanding how to use the find() function, you will gain a valuable tool for string manipulation and pattern matching, making your code more versatile and efficient.

What is the Find Function in Python?

The find() function in Python is a built-in method that allows you to search for a specific substring within a larger string. It returns the index of the first occurrence of the substring if found, or -1 if the substring is not present. This function provides a convenient way to locate patterns or sequences of characters within a string, enabling you to perform various operations such as extracting data, validating inputs, or manipulating text.

Syntax of the Find Function

index = string.find(substring, start, end)

Here, the string is the string that you want to search in, the substring is the string that you want to search for, the start is the starting index of the search, and the end is the ending index of the search.

If the start and end are not specified, the find function will search the entire string. If the start is specified, the search will start from that index. If the end is specified, the search will end at that index.

Parameters of Find Function in Python

The find function in python takes three parameters:

• substring: This is the required parameter, and it is the substring that you want to search for in the string. It could be a string or a single character.
• start: This is an optional parameter, and it is the starting index of the search. The starting index of the search indicates where the search for the substring within the string should begin. Its usage is not mandatory, and if not specified, the search will begin at index 0 by default.
• end: This is also an optional parameter, and it is the ending index of the search. It specifies where to end the search for the substring in the string. The default value of this parameter is the length of the string.

Return Value of Find Function in Python

If the substring is present in the string, the find function returns the index of the first character of the substring and if the substring is not present in the string, it returns -1.

Here is an example that demonstrates the return value of the find() function:

string = "Hello, PrepBytes!"
substring = "PrepBytes"
index = string.find(substring)
print(index)

Output:

7

Explanation – This example demonstrates the usage of the find() function to look for the sub-string "PrepBytes" in the string "Hello, PrepBytes!". The find function returns the index 7 since the sub-string is located at that index within the string. If the sub-string is changed to "World", which is not present in the string, the find() function will return -1 to indicate that the sub-string was not found.

Examples of Find Function in Python

Let’s look at some examples of how to use the find function in Python:

Example – 1
Below is code implementation and explanation:

string = "Hello, PrepBytes!"
substring = "prepBytes"
index = string.find(substring)
print(index)

Output:

-1

Explanation: This particular example involves searching for the index of the sub-string "prepBytes" in the string "Hello, PrepBytes!". Unfortunately, the sub-string is not present in the string, resulting in the find function returning -1 to signify that the sub-string could not be found.

Example – 2
Below is code implementation and explanation:

string = "Hello, PrepBytes!"
substring = "y"
index = string.find(substring, 5, 13)
print(index)

Output:

12

Explanation: This example focuses on searching for the sub-string "y" in the string "Hello, PrepBytes!" but exclusively between the indices 5 and 13. The find function is used to locate the first occurrence of the sub-string within that specific range, which happens to be at index 12. Therefore, the find function returns the value 12 as the index of the first occurrence of the sub-string within the specified range.

Example – 3
Below is code implementation and explanation:

string = "Hello, prepBytes!"
substring = "e"
index = string.find(substring, 2)
print(index)

Output:

9

Explanation: In this example, we are searching for the substring "e" in the string "Hello, PrepBytes!" starting from index 2. The find function returns the index of the first occurrence of the substring after that index, which is 9.

Example – 4
Below is code implementation and explanation:

string = "Hello, C! Hello, C++! Hello, Python! Hello, Java!"
substring = "Hello"
start = 0
while True:
    index = string.find(substring, start)
    if index == -1:
        break
    print(index)
    start = index + 1

Output:

0
10
22
37

Explanation: In this example, we are searching for the substring "Hello" within the string "Hello, C! Hello, C++! Hello, Python! Hello, Java!" and print the index of each occurrence. We are using a while loop to keep searching for the substring until it is no longer found. The start variable is used.

Conclusion
In conclusion, the find() function in Python provides a powerful and versatile tool for searching and locating substrings within strings. It allows you to efficiently search for specific patterns or sequences of characters and retrieve their starting positions within a string. By understanding the syntax, parameters, and techniques of the find() function, you can effectively manipulate strings, extract data, and validate inputs in your Python code.
Throughout this article, we have explored the basic usage of the find() function, including specifying the substring to search for and defining the search scope with the optional start and end parameters. We have also discussed various examples and use cases where the find() function can be applied, such as extracting specific parts of a string, checking for the presence of certain patterns, or determining the location of elements.

FAQs Related to Find function in Python

Q1: Does the find() function consider case sensitivity?
A1: Yes, by default, the find() function is case sensitive. This means that the search is sensitive to uppercase and lowercase characters. To perform a case-insensitive search, you can convert both the string and the substring to a consistent case using the lower() or upper() methods.

Q2: What happens if the substring is not found by the find() function?
A2: If the substring is not found within the string, the find() function returns -1. This can be useful for checking the existence of a substring before further operations or branching in your code.

Q3: Can I use negative values for the start and end parameters?
A3: Yes, you can use negative values for the start and end parameters to search from the end of the string. For example, string.find("substring", -5, -1) will search for the substring within the last five characters of the string.

Q4: Are there alternatives to the find() function?
A4: Yes, Python provides other methods for string searching and manipulation, such as index(), startswith(), endswith(), regular expressions (re module), and more. The choice of method depends on your specific requirements and the complexity of the search pattern.