Loops in Python

Loops are used to repeat a block of code multiple times. Python provides two main types of loops: for loops and while loops.

The for Loop

A for loop is used for iterating over a sequence (that is either a list, a tuple, a dictionary, a set, or a string).

Iterating Over a List

fruits = ["apple", "banana", "cherry"]
for fruit in fruits:
    print(fruit)

The range() Function

To loop through a set of code a specified number of times, we can use the range() function.

# Iterates from 0 to 4
for i in range(5):
    print(i)

You can also specify a start value, an end value, and a step value:

# Iterates from 2 to 10 with a step of 2
for i in range(2, 11, 2):
    print(i) # Output: 2, 4, 6, 8, 10

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The while Loop

The while loop executes a set of statements as long as a condition is true.

count = 1
while count <= 5:
    print(count)
    count += 1

[!IMPORTANT] Always ensure the condition in a while loop eventually becomes false; otherwise, you will create an infinite loop.

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Loop Control Statements

Python provides statements to change the execution from its normal sequence.

The break Statement

The break statement is used to exit the loop prematurely.

for i in range(10):
    if i == 5:
        break
    print(i) # Prints 0 to 4

The continue Statement

The continue statement skips the current iteration and moves to the next one.

for i in range(5):
    if i == 2:
        continue
    print(i) # Prints 0, 1, 3, 4

The pass Statement

The pass statement is a null operation; it is used as a placeholder when a statement is required syntactically but no action is needed.

for i in range(5):
    pass # Do nothing

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The else Clause in Loops

Python allows an else block after a for or while loop. The else block is executed only if the loop completes normally (i.e., it was not terminated by a break).

for i in range(5):
    print(i)
else:
    print("Loop completed successfully!")