Accessing List Items in Python

In Python, a list is a sequence. Each object in the list can be accessed by its index. The index starts at 0. The index, or the last item in the list, is “length – 1”. To access a value in a list, you use square brackets to slice it and use the index or index to get the value at that index.

The slice operator gets one or more items from a list. Put the index in square brackets to retrieve the item at that position.

obj = list1[i]

Example 1

Take a look at the following example –

list1 = ["Rohan", "Physics", 21, 69.75]
list2 = [1, 2, 3, 4, 5]

print ("Item at 0th index in list1: ", list1[0])
print ("Item at index 2 in list2: ", list2[2])

It will produce the following output –

Item at 0th index in list1: Rohan
Item at index 2 in list2: 3

Python allows negative indices in any sequence type. The “-1” index represents the last item in the list.

Example 2

Let’s look at another example: −

list1 = ["a", "b", "c", "d"]
list2 = [25.50, True, -55, 1+2j]

print ("Item at index 0 in list1: ", list1[-1])
print ("Item at index 2 in list2: ", list2[-3])

It will produce the following output. −

Item at index 0 in list1: d
Item at index 2 in list2: True

The slice operator extracts a sublist from the original list.

Sublist = list1[i:j]

Parameters

• i − The index of the first item in the sublist

• j − The index of the item immediately following the last item in the sublist

This will return a slice from item i to item (j-1) in list1.

Example 3

In slicing, both “i” and “j” are optional. If not used, “i” defaults to 0, and “j” to the last item in the list. Negative indices are supported in slicing. See the following example −

list1 = ["a", "b", "c", "d"]
list2 = [25.50, True, -55, 1+2j]

print ("Items from index 1 to 2 in list1: ", list1[1:3])
print ("Items from index 0 to 1 in list2: ", list2[0:2])

This will produce the following output −

Items from index 1 to 2 in list1: ['b', 'c']
Items from index 0 to 1 in list2: [25.5, True]

Example 4

list1 = ["a", "b", "c", "d"]
list2 = [25.50, True, -55, 1+2j]
list4 = ["Rohan", "Physics", 21, 69.75]
list3 = [1, 2, 3, 4, 5]

print ("Items from index 1 to last in list1: ", list1[1:])
print ("Items from index 0 to 1 in list2: ", list2[:2])
print ("Items from index 2 to last in list3", list3[2:-1])
print ("Items from index 0 to index last in list4", list4[:])

It will produce the following output –

Items from index 1 to last in list1: ['b', 'c', 'd']
Items from index 0 to 1 in list2: [25.5, True]
Items from index 2 to last in list3 [3, 4]
Items from index 0 to index last in list4 ['Rohan', 'Physics', 21, 69.75]