Learning python - For and While Loops

For loops

A for loop lets you repeat code without writing the same line many times. It is useful when you want to perform the same action for every item in a list.

Without a for loop (the long way)

print("Buy milk")
print("Buy bread")
print("Buy apples")
print("Buy coffee")
print("Buy pasta")

With a for loop (shorter and cleaner)

shopping = ["milk", "bread", "apples", "coffee", "pasta"]

for item in shopping:
    print("Buy " + item)

Explanation:
for item in shopping means: "Go through each item in the list called shopping, and for each one, run the code inside the loop."

Using `break` in a for loop

break stops the loop early.

tasks = ["email", "report", "meeting", "break", "presentation"]

for task in tasks:
    if task == "break":
        print("Taking a break now.")
        break
    print("Working on:", task)

Explanation:
The loop stops as soon as it reaches break. This is useful when you only want to loop until something happens.

Using `range()` in a for loop

range() lets you loop a set number of times.

for number in range(5):
    print("Loop number:", number)

Explanation:
range(5) creates numbers 0, 1, 2, 3, 4. It is useful when you want a loop to run a specific number of times.

While loops

A while loop runs while a condition is true. It stops when the condition becomes false.

Simple while loop example

count = 1

while count <= 3:
    print("Count is:", count)
    count += 1

Explanation:
The loop repeats until count becomes greater than 3.

While loop with a for loop inside

attempts = 0

while attempts < 2:
    print("Attempt:", attempts + 1)

    for letter in ["A", "B", "C"]:
        print("Checking option:", letter)

    attempts += 1

Explanation:
The while loop runs twice. Inside it, the for loop runs through the list ["A", "B", "C"] each time. This is helpful when you need repeated cycles, and each cycle has several steps.

Vivienne Reay