Loops are one of the first concepts that make code powerful. Instead of repeating lines manually, you write a repeat rule and let Python handle the iteration.
The for loop
Use a for loop when you already know the sequence you want to iterate over, such as a list, tuple, string, or range.
fruits = ["apple", "banana", "cherry"]
for fruit in fruits:
print(fruit)
For index-style iteration, range() is the usual choice:
for i in range(5):
print(i)The while loop
Use while when repetition depends on a condition that may change during execution.
count = 1
while count <= 5:
print(count)
count += 1
A while loop can become infinite if the condition never changes. Always ensure state updates are explicit.
Loop control tools
break: stop the loop immediately.continue: skip the current iteration and move to the next.pass: placeholder used where syntax requires a statement.
Practical advice for beginners
- Print intermediate values while learning loop behavior.
- Start with short sequences before handling large datasets.
- Use descriptive variable names so loop intent is obvious.
Most loop mistakes are not syntax issues. They are logic issues around condition design and state updates.