Python List index() - Find Index of Item
index() method in Python is a helpful tool when you want to find the position of a specific item in a list. It works by searching through the list from the beginning and returning the index (position) of the first occurrence of the element you're looking for. Example:
a = ["cat", "dog", "tiger"]
print(a.index("dog"))
Output
1
Explanation: index("dog") method finds the first occurrence of "dog" in the list a. Since "dog" is at index 1, it returns 1.
Syntax of List index() method
list.index(element, start, end)
Parameters:
- element (required): The item to search for.
- start (optional): Index to start the search from (default is 0).
- end (optional): Index to end the search (exclusive, default is end of list).
Returns:
- The first index of element in the list within the specified range.
- Raises ValueError if the element is not found.
Examples of List index()
Example 1: In this example, we are searching for the index of the number 40 within a specific range of the list from index 4 to 7 .
a = [10, 20, 30, 40, 50, 40, 60, 40, 70]
res = a.index(40, 4, 8)
print(res)
Output
5
Example 2: In this example, we try to find the index of 'yellow' in the list and handle the error with a try-except block if it's not found.
a = ['red', 'green', 'blue']
try:
index = a.index('yellow')
print(a)
except ValueError:
print("Not Present")
Output
Not Present
Example 3: In this example, we are finding the index of the tuple ("Bob", 22) in a list of tuples and index() will return the position of its first occurrence.
a = [("Alice", 21), ("Bob", 22), ("Charlie", 20), ("Bob", 24)]
res = a.index(("Bob", 22))
print(res)
Output
1
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