What are loops in programming?

Loops are control structures that allow you to execute a block of code multiple times until a certain condition is met or until the elements in a sequence are exhausted.

In Python, there are three main types of loops:

• while
• for
• Loops using generators and iterators (although this is more of a concept based on for)

while loop

Executes a block of code as long as the condition is true.

# Example of a while loop
count = 0
while count < 5:
    print(f"Iteration {count}")
    count += 1

for loop

Iterates over elements of a sequence (list, tuple, string, dictionary, etc.) or an iterable object.

# Example of a for loop
fruits = ["apple", "banana", "cherry"]
for fruit in fruits:
    print(fruit)

for can be used with the range() function to perform a specific number of iterations.

# Example of a for loop with range()
for i in range(3):
    print(f"Just number: {i}")

Keywords for controlling loops:

• break: Completely terminates the loop.
• continue: Skips the remaining part of the current iteration and proceeds to the next.

# Example of break
for i in range(10):
    if i == 5:
        break  # Exit the loop
    print(i)

# Example of continue
for i in range(10):
    if i % 2 == 0:
        continue # Proceed to the next iteration
    print(i)

else clause in loops:

In Python, for and while loops can have an optional else block. This block executes only if the loop terminates naturally (i.e., not interrupted by break).

# Example of else with for
for i in range(3):
    print(f"Inside loop: {i}")
else:
    print("Loop finished without break")

# Example of else with while
count = 0
while count < 3:
    print(f"Counter: {count}")
    count += 1
else:
    print("Condition became false")

Loops and iterators/generators:

The for loop in Python actually works using the iterator protocol. Any object implementing __iter__() and __next__() methods can be used in a for loop. Generators are a convenient way to create iterators.

# Example of a simple generator
def my_generator():
    yield 1
    yield 2
    yield 3

for value in my_generator():
    print(value)

Comparison of for and while:

Feature	for	while
Purpose	Iterate over a sequence/iterator	Execute as long as the condition is true
Termination	Exhaustion of elements / break	Condition becomes false / break
Usage	When the number of iterations is known or when iterating over a collection	When the number of iterations is unknown in advance

The choice of loop type depends on the specific task.