Overview
This lecture explains the limitations of Python's input function when accepting lists from users and demonstrates how to use loops to correctly input multiple items and store them as a list.
Problem with the Input Method
- The input() function always returns user input as a string, not as separate data elements.
- When entering multiple numbers (e.g., "67 48 90"), input() stores them as a single string, not as a list of integers.
- If stored directly, the string "67 48 90" is treated as individual characters in a list, not as numbers.
Input a List Using Loops
- To store multiple numbers as a list, first ask the user how many elements to enter using:
n = int(input("Enter the number of elements")).
- Initialize an empty list with:
numbers = [].
- Use a for loop to repeat the input process:
for i in range(n):.
- For each iteration, receive an integer input with:
x = int(input()).
- Append each integer to the list using:
numbers.append(x).
- The final list contains separate integer items as intended.
Key Terms & Definitions
- input() — Function to receive input from the user, always returns a string.
- Typecasting — Converting data from one type to another (e.g., string to integer with int()).
- List — An ordered collection of items in Python.
- append() — List method to add an item to the end of a list.
- for Loop — A control flow statement used to repeat a block of code multiple times.
Action Items / Next Steps
- Practice writing a Python program that inputs a list of user numbers using a loop.
- Review previous presentation notes on receiving and typecasting user input.