Python Lists: Index Method

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The index() method in Python is used with lists (and also works on tuples and strings) to find the position of the first occurrence of a given element.

✅ Why We Use index()

We use the index() method when we want to find the position (index number) of an item in a list. This is helpful when:

• You need to know where an item is located in a list.
• You want to modify or remove an item by its position.
• You need to match data from two lists using positions.

🔤 Syntax

list_name.index(element, start, end)

• element: The item to search for.
• start (optional): Start searching from this index.
• end (optional): Stop searching at this index (exclusive).

🧒 Beginner Example

fruits = ["apple", "banana", "cherry", "banana"]
print(fruits.index("banana"))  # Output: 1

It returns 1 because the first occurrence of "banana" is at index 1.

⛔ If the item is not found

print(fruits.index("orange"))  # Error!

This will raise a ValueError because "orange" is not in the list.

📌 Using start and end

print(fruits.index("banana", 2))  # Output: 3

This starts searching from index 2 and finds the second "banana" at index 3.

🌍 Real-World Example

Suppose you are building a to-do list app and you want to know where a task is located:

tasks = ["Buy groceries", "Do laundry", "Pay bills", "Call mom"]
task_to_find = "Pay bills"

position = tasks.index(task_to_find)
print(f"'{task_to_find}' is at position {position}")

🟢 Output:

'Pay bills' is at position 2

This could help you highlight the task in the app or remove it after completion.

• List Index Method: Find the Index of an Element in a List

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