Question

What will the following code display? numbers = [1, 2, 3, 4, 5] my_list = numbers[1:] print(my_list)

Short answer

Answer: The output of the given code will be [2, 3, 4, 5].

Step-by-step solution

Understanding the code and list slicing

The given code defines a list called 'numbers' with elements 1 through 5. Then, it creates another list 'my_list' by slicing the 'numbers' list. The slice notation is [1:], which means that 'my_list' should contain elements from the 'numbers' list starting at index 1 (2nd element) up to the end of the list.

Calculate the output of the slicing operation

'numbers' is sliced from index 1 to the end, so we take the elements in 'numbers' from the second element onwards: 2, 3, 4, 5. Thus, 'my_list' will contain [2, 3, 4, 5].

Predict the output of the print statement

The print statement will display the content of the 'my_list', which is the result of our list slicing operation. Therefore, the output of the given code will be: [2, 3, 4, 5]

Key concepts

List Indexing

List indexing is how we access elements in a list using their position within that list. In Python, list indices start at 0. This means the first element in a list is accessed using index 0, the second element with index 1, and so on. It might seem slightly confusing at first, but once you get the hang of it, you will find it very logical.
For example, given a list

• numbers = [1, 2, 3, 4, 5]

you can access its first element by writing `numbers[0]`, which will give you `1`. Similarly, `numbers[3]` will give you `4`, because indices start counting from zero. Understanding list indexing is crucial for working with data in Python, as it provides a straightforward way to manipulate and use data stored in lists.

Slicing Notation

Slicing notation is a convenient way to access a portion or "slice" of a list, allowing you to retrieve multiple elements. In Python, slicing is performed using the colon `:`. The basic syntax for slicing is:

• list[start:end]

Here, 'start' is the index where the slice begins, and 'end' is the index before which the slice stops. Importantly, the element at the 'end' index is not included in the slice.
A slice can also be defined to include every 'nth' element using a third 'step' parameter:

• list[start:end:step]

In our example, the slice `numbers[1:]` means "start at index 1 and go to the end of the list," resulting in `[2, 3, 4, 5]`. When the slice's start or end index is omitted, Python defaults to the start or end of the list, respectively. Practicing slicing can help you efficiently retrieve data without looping through lists, saving both time and computing resources.

List Operations

List operations in Python allow you to perform a wide range of tasks that manipulate list contents. With list operations, you can add, remove, or change elements, all by using simple commands.

• Adding Elements: Use `.append()` to add a single element at the end, or `.extend()` to add multiple elements. There is also `.insert(index, element)` to place an element at a specific position.
• Removing Elements: Use `.remove(element)` to delete a specific value, or `.pop(index)` to remove a value from a specific position. `.clear()` is used to remove all elements from the list.
• Changing Elements: Directly alter elements using list indexing. For instance, `numbers[2] = 10` changes the third element in the list to `10`.

These operations form the backbone of many algorithms and data transformations in Python. By mastering them, you can unlock a powerful toolkit for handling data efficiently and effectively in your programming projects.