Access List Items in Python

How to Access List Items

In Python, lists are data structures that allow you to store multiple items in a single variable. This lesson will cover various methods to access list items, including positive and negative indexing, ranges of indexes, and checking for the existence of items.

1. Access List Items

List items are indexed, meaning you can access them by referring to their index number. Python uses zero-based indexing, which means the first item has an index of 0.

Example:

To print the second item of a list:

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thislist = ["apple", "banana", "cherry"]
print(thislist[1])  # Output: banana

2. Negative Indexing

Negative indexing allows you to access list items from the end of the list. In this case, -1 refers to the last item, -2 refers to the second last item, and so on.

Example:

To print the last item of the list:

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thislist = ["apple", "banana", "cherry"]
print(thislist[-1])  # Output: cherry

3. Range of Indexes

You can specify a range of indexes to access multiple items from a list. When you specify a range, the return value will be a new list containing the specified items.

Example:

To return the third, fourth, and fifth items:

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thislist = ["apple", "banana", "cherry", "orange", "kiwi", "melon", "mango"]
print(thislist[2:5])  # Output: ['cherry', 'orange', 'kiwi']

Note: The search starts at index 2 (included) and ends at index 5 (not included).

Leaving Out the Start Value

If you leave out the start value, the range will start from the beginning of the list.

Example:

To return items from the beginning to, but not including, "kiwi":

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thislist = ["apple", "banana", "cherry", "orange", "kiwi", "melon", "mango"]
print(thislist[:4])  # Output: ['apple', 'banana', 'cherry', 'orange']

Leaving Out the End Value

If you leave out the end value, the range will go on to the end of the list.

Example:

To return items from "cherry" to the end:

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thislist = ["apple", "banana", "cherry", "orange", "kiwi", "melon", "mango"]
print(thislist[2:])  # Output: ['cherry', 'orange', 'kiwi', 'melon', 'mango']

4. Range of Negative Indexes

You can also specify negative indexes to start the search from the end of the list.

Example:

To return items from "orange" (-4) to, but not including "mango" (-1):

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thislist = ["apple", "banana", "cherry", "orange", "kiwi", "melon", "mango"]
print(thislist[-4:-1])  # Output: ['orange', 'kiwi', 'melon']

5. Checking if an Item Exists

To determine if a specific item is present in a list, you can use the in keyword. This will return True if the item exists and False otherwise.

Example:

To check if "apple" is present in the list:

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thislist = ["apple", "banana", "cherry"]
if "apple" in thislist:
    print("Yes, 'apple' is in the fruits list")  # Output: Yes, 'apple' is in the fruits list