Day 9: Creating Custom Lists

Overview

Learn how to create a Python program that allows users to build custom lists with different data types. This exercise covers user input handling, loops, and type operations.

Learning Objectives

  • Handle user input for list creation
  • Implement type validation
  • Work with dynamic lists
  • Practice error handling

Implementation Details

1. User Input for List Length

The program starts by getting the desired list length from the user:

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limit = int(input("Enter length of list: "))

2. List Initialization

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i = 0
L = []

3. Element Collection Loop

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while i < limit:
    ty = input("Enter data type (S for String / N for Number): ").upper()
    
    if ty == "S":
        element = input("Enter the string element: ")
        L.append(element)
        i += 1
    elif ty == "N":
        try:
            element = int(input("Enter the number element: "))
            L.append(element)
            i += 1
        except ValueError:
            print("Invalid input! Please enter a number.")
    else:
        print("Invalid type! Please enter 'S' or 'N'.")

4. Result Display

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print("Final List:", L)

Example Usage

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Enter length of list: 3
Enter data type (S for String / N for Number): S
Enter the string element: Hello
Enter data type (S for String / N for Number): N
Enter the number element: 42
Enter data type (S for String / N for Number): S
Enter the string element: World
Final List: ['Hello', 42, 'World']

Key Concepts

  • Type conversion using int()
  • Exception handling with try/except
  • List manipulation with append()
  • String methods like upper()

Practice Exercises

  1. Modify the program to accept floating-point numbers
  2. Add validation for string inputs (e.g., minimum length)
  3. Implement a feature to remove elements from the list
  4. Add support for more data types (e.g., boolean, complex numbers)