Input a List Using Loops in Python

Key Topics Covered

• Problem with the Input Method
• Input a List Using Loops

Problem with the Input Method

• Issue: input() always returns user input as a string.
• Example:
  • When asking for a list of numbers: numbers = input("Enter a list of numbers")
  • User enters: "67 48 90"
  • Problem: Treated as a single string, not separate list items.

Visual Example

• Expected: [67, 48, 90] (with indices 0, 1, 2)
• Actual: ['6', '7', ' ', '4', '8', ' ', '9', '0'] (8-character string list)

Input a List Using Loops

Steps and Commands

1. Receive the Number of Elements

   n = int(input("Enter the number of elements"))
   • Input is typecast to an integer.

2. Create an Empty List

   numbers = []

3. Use a For Loop to Receive Individual Items

   for i in range(n): x = int(input()) numbers.append(x)
   • **Details: **
     • range(n): Loop runs n times.
     • int(input()): Typecast input to integer and store in x.
     • numbers.append(x): Add x to the numbers list.

Example Walkthrough

1. Prompt and Receive Number of Elements

   • User enters: 3
   • n now points to 3 (integer).

2. Create Empty List

   • Command: numbers = []

3. For Loop Execution

   • Loop runs 3 times (0 to 2).
   • **First Iteration: **
     • User input: 67
     • x points to 67
     • numbers.append(x) adds 67 to numbers list. List now: [67].
   • Second Iteration:
     • User input: 48
     • x points to 48
     • numbers.append(x) adds 48 to numbers. List now: [67, 48].
   • Third Iteration:
     • User input: 90
     • x points to 90
     • numbers.append(x) adds 90 to numbers. List now: [67, 48, 90].

4. Check the Final List

   print(numbers)
   • Output: [67, 48, 90]

Conclusion

• Successfully input a list of numbers using loops.
• Able to handle each element separately and store in a list as integers.