Question

Write a program that initializes a list with ten random integers and then prints four lines of output, containing \- Every clement at an cven index. \- Every even element. \- All elements in reverse order. \- Only the first and last element.

Short answer

The list will be initialized and displayed based on specified criteria like even indices and even elements, reversed order, and first/last elements.

Step-by-step solution

Import Required Libraries

Import the random library, which will be used to generate random integers. This is an important first step because generating random numbers requires this module.

Initialize the List with Random Integers

Create a list of ten random integers. Use a loop to populate the list and the random.randint() function to generate numbers in a specific range.

Print Elements at Even Indices

Iterate through the list using an index, checking if the index is even, and then print the element at that index.

Print Every Even Element

Iterate through the list, check if each element is even (using the modulo operator), and print the element if this condition is met.

Print Elements in Reverse Order

Utilize Python's list slicing to reverse the list and print the elements in this reversed order.

Print First and Last Elements

Access the first element at index 0 and the last element using negative indexing (-1) and print them to the console.

Key concepts

Random Integers

When programming in Python, generating random integers can be incredibly useful for various applications like simulations or random sampling. A random integer is a number chosen from a set within a specific range. To generate these random numbers, Python provides the `random` library.

To use this library:

• First, import it using `import random`.
• Use the `random.randint(a, b)` function, where `a` is the start of the range and `b` is the end. This function returns a random integer between `a` and `b`, inclusive.
• For example, `random.randint(1, 100)` will generate a number between 1 and 100.

By understanding how to generate random integers, you can add variability and unpredictability to your programs, making them more flexible and powerful.

List Indexing

Lists in Python are ordered collections of items, and each item has an index (or position). Understanding list indexing is crucial for accessing elements efficiently.

Here are some key points:

• Indexing starts at 0. For example, in the list `[10, 20, 30]`, the element `10` is at index 0, `20` is at index 1, and so on.
• Using negative indices, you can access elements from the end of the list, with `-1` being the last element.
• To access even indexed elements in a list of 10, you would check indices 0, 2, 4, 6, and 8.

Understanding how to work with indices allows you to extract and manipulate specific elements within your lists easily.

Even Numbers

An even number is any integer that is exactly divisible by 2, meaning when divided by 2, it leaves no remainder. In Python, checking if a number is even can be done using the modulo operator `%`.

Here's how you can determine if a number is even:

• Use the expression `number % 2 == 0`. If this evaluates to `True`, the number is even.
• For example, `8 % 2 == 0` is `True` because 8 is divisible by 2 evenly.

Implementing this logic, you can easily filter and print the even numbers from a list, aiding in tasks like data filtering or pattern recognition.

Python List Slicing

List slicing in Python is a powerful feature that allows you to access a range of elements in a list. This method is often used for creating copies or sublists without altering the original list.

Here's how slicing works:

• The syntax for slicing is `list[start:stop:step]`.
• The `start` index is inclusive and `stop` is exclusive. If `start` is omitted, it defaults to the beginning of the list, and if `stop` is omitted, it defaults to the end of the list.
• The `step` is optional and determines the stride; specifying `-1` will reverse the list.

For example, to print a list in reverse, you would use `list[::-1]`, which means to iterate from the end to the beginning.
Mastering list slicing lets you organize and access data more efficiently.