Notes on Loops in Python

Introduction to Loops

• Loops are used to repeat tasks multiple times.
• Example: Sending a message to a user and retrying if it fails.

For Loop Structure

• Basic Syntax: for number in range(3): # Code to repeat
• range(n) generates numbers from 0 to n-1.
• Indentation is crucial in Python to define blocks of code.

Using range() Function

• range() takes up to three arguments:
  1. start: Starting number (default is 0).
  2. stop: End number (exclusive).
  3. step: Increment (default is 1).
• Example: for number in range(1, 4): print(number)
  • Output: 1, 2, 3
• Multiplying Strings:
  • String multiplied by a number repeats the string.

Breaking Out of Loops

• Use the break statement to exit a loop.
• Example: if successful: break

Handling Failed Attempts

• Use an else statement with a loop to handle cases where the loop did not break.
• Example: else: print('Attempted 3 times and failed')

Nested Loops

• A loop inside another loop (outer loop and inner loop).
• Example: for x in range(5): for y in range(3): print(f'({x}, {y})')
• Output: Coordinates (0,0), (0,1), ..., (4,2).

Understanding range() Function

• Returns a range object which is iterable.
• Can be used in a for loop or with other iterable types (like strings and lists).

Exercise: Display Even Numbers

1. Write a program to display even numbers from 1 to 10.
2. Use range(1, 10).
3. Check if a number is even using modulus operator:

4. Count the even numbers with a separate variable.

Conclusion

• Summary of key points on loops and the range() function.
• Encourage further learning with additional resources.