Python String index() Method

Python index() method is same as the find() method except it returns error on failure. This method returns index of first occurred substring and an error if there is no match found.

Signature

Parameters

sub : substring
start : start index a range
end : last index of the range

Return Type

If found it returns an index of the substring, otherwise an error ValueError.

Let's see some examples to understand the index() method.

Python String index() Method Example 1

# Python index() function example
# Variable declaration
str = "Welcome to the Javatpoint."
# Calling function
str2 = str.index("at")
# Displaying result
print(str2)

Output:

Python String index() Method Example 2

An error is thrown if the substring is not found.

# Python index() function example
# Variable declaration
str = "Welcome to the Javatpoint."
# Calling function
str2 = str.index("ate")
# Displaying result
print(str2)

Output:

ValueError: substring not found

Python String index() Method Example 3

We can also pass start and end index as parameters to make process more customized.

# Python index() function example
# Variable declaration
str = "Welcome to the Javatpoint."
# Calling function
str2 = str.index("p",19,21)
# Displaying result
print("p is present at :",str2,"index")

Output: