Question

Write a program that inputs a string and prints the string backward. Convert all uppercase characters to lowercase and all lowercase characters to uppercase.

Short answer

Write a Python program to reverse the string and swap the case using string slicing and swapcase().

Step-by-step solution

Understand the Problem

The task requires creating a program that takes a user-inputted string, reverses the string, and switches the case of each character within the string.

Plan the Solution

To solve this, we need to follow these steps: (1) Accept input from the user, (2) Reverse the string, (3) Swap the case of each character, (4) Print the result.

Write the Code

Here's how you can implement the solution in Python: ```python # Step 1: Accept the string from the user input_string = input('Enter a string: ') # Step 2: Reverse the string reversed_string = input_string[::-1] # Step 3: Swap case of each character swapped_string = reversed_string.swapcase() # Step 4: Print the result print(swapped_string) ```

Test the Program

Run the program with various example inputs: - If the input is 'Hello World', the output should be 'DLROw OLLEh'. - For 'Python3.8', the output should be '8.3NOHTYp'. Check that the program effectively reverses the string and swaps the case of all characters.

Key concepts

Case Conversion

In programming, case conversion involves changing the letters in a string from uppercase to lowercase and vice versa. In Python, this can be done easily using the `swapcase()` function.
If you have a string like 'Hello World', applying `swapcase()` would transform it to 'hELLO wORLD'. This function checks each character in the string:

• If the character is uppercase, it converts it to lowercase.
• If the character is lowercase, it changes it to uppercase.
• Non-alphabetic characters remain unchanged.

Case conversion is particularly useful in scenarios where you need to change text formats, ensure consistency in text input, or as in our exercise, when combined with other manipulations like string reversal.

String Reversal

String reversal is a simple yet powerful method of manipulating strings, where the characters in a string are ordered in reverse. In Python, you can achieve this quickly using slicing.
The syntax for reversing a string `s` is `s[::-1]`, which generates a new string with characters in the reverse order from the original. Let's consider a string 'Python'. If we reverse it, we get 'nohtyP'.

• The `start` parameter of slicing is left empty, indicating the beginning of the string.
• The `stop` parameter is also empty, suggesting the end of the string.
• The `step` parameter is set to `-1`, which dictates traversing the string backward one character at a time.

This technique is often combined with other string manipulations, such as case conversion, to create complex transformations of input strings.

User Input Handling

Handling user input is a foundational concept in programming, especially when creating interactive applications. In Python, you use the `input()` function to receive input from a user.
This function reads a line from the input and returns it as a string. For instance, `user_input = input('Enter your text: ')` prompts the user with 'Enter your text: ' and stores their input in `user_input`.

• The prompt message is optional but helps guide the user.
• The input is always received as a string, so for numerical data, further conversion is needed.
• Handling exceptions and errors is a best practice to ensure the application remains robust, such as expecting a specific format or type.

Effective user input handling allows the program to behave predictably and securely, engaging the user in a meaningful way.

Python Programming Basics

Python is a versatile language known for its simplicity and readability. It offers numerous built-in functions and features that streamline the process of coding.
Some key programming basics in Python include:

• Variables: Used to store data values, declared simply with assignment like `x = 5`.
• Data Types: Python supports various data types such as integers, strings, and lists, which are defined upon assigning a value to them.
• Functions: Blocks of reusable code defined with `def` keyword, for instance, `def my_function():`.
• Loops and Conditionals: Control flow tools like `if`, `for`, and `while` for iterating and making decisions in code.
• Libraries: Extensive libraries and frameworks available via the `import` statement empower development.

Understanding these basics enables one to solve problems effectively and build a variety of applications, from simple scripts to complex web services.