How to Utilize Values in a List
To utilize values within a list, you use an index
that starts from 0.
The index of the first element is 0
, the second element is 1
, and it increases sequentially after that.
The index of the last element is -1
, the second-to-last is -2
, decreasing sequentially.
fruits = ["Apple", "Banana", "Grape", "Cherry"] # First element first_fruit = fruits[0] # "Apple" print("first_fruit:", first_fruit) # Second element second_fruit = fruits[1] # "Banana" print("second_fruit:", second_fruit) # Last element last_fruit = fruits[-1] # "Cherry" print("last_fruit:", last_fruit)
Slicing to Retrieve a Portion of a List
To retrieve a portion of a list, we use slicing
.
Slicing is a method that uses list indices to extract the desired portion.
To slice a list, you specify the start and end index separated by a colon :
inside the square brackets []
.
For example, you can slice the fruits
list with fruits[0:2]
.
The start index is included, but the end index is not.
For example, fruits[0:2]
extracts from the first element to the second element.
The third element, fruits[2]
, is not included in the result of the slice.
fruits = ["Apple", "Banana", "Grape", "Cherry"] # From the first element to the second element first_two_fruits = fruits[0:2] # fruits[2] is not included print("first_two_fruits:", first_two_fruits) # ['Apple', 'Banana']
Nested Lists
A nested list
refers to a list that includes other lists as its elements.
This allows you to represent complex data structures like multidimensional arrays or matrices.
# Create a 2D list nested_list = [[1, 2, 3], [4, 5, 6], [7, 8, 9]] # First element of the nested list print(nested_list[0]) # Output: [1, 2, 3] # Specific element of a nested list print(nested_list[0][1]) # Output: 2 (2nd element of the 1st list)
What is the correct index to fill in the blank?
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