Task_13_for_loops.md

Task 13 - For loops

A for loop repeats a block of code for every item in a sequence. That sequence can be numbers from range, the letters in a string, the elements of a list, and so on.

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Demo 1 - Counting with range

range(start, stop, step) generates numbers up to but not including stop.

# Count from 1 up to (but not including) 4
for number in range(1, 4):          # 1 2 3
    print(number, number * ".")     # 1 .   2 ..   3 ...

You can add a third argument to set the step size.

# Count from 1 to 9 in steps of 2
for number in range(1, 10, 2):      # 1 3 5 7 9
    print(number)

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Demo 2 - Stopping early with break and using else

break ends the loop immediately. An optional else block runs only if the loop finishes without hitting break.

successful = False

for attempt in range(3):
    print("Attempt", attempt + 1)
    if successful:
        print("Succeeded")
        break
else:                               # runs because break was never reached
    print("All attempts failed")

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Demo 3 - Looping over other iterables

Any object that can return its items one at a time is an iterable.

# Each character in a string
for char in "Python":
    print(char)

# Each element in a list
for fruit in ["apple", "banana", "pear"]:
    print(f"I like {fruit}")

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Your exercise

1. Create a file called Task_13.py.

2. Write a loop that prints the numbers 1 through 5, each followed by that many asterisks, like 3 ***.

3. Use a second loop with the range 10 - 0 to print even numbers downward in steps of two: 10 8 6 4 2.

4. Prompt the user to enter a secret word. Give them up to 3 tries.

   • If they guess correctly, print "Access granted" and end the loop with break.
   • If they fail all three attempts, print "Access denied" after the loop using the else clause.

5. Make a list named hobbies with at least three items. Loop through it and print "I enjoy <hobby>" for each one.

Run the script, experiment with different inputs, and watch how range, break, and else control the flow of your loops.