How to use for loop in Python

A for loop in Python is used to iterate over a sequence (like a list, tuple, string, or range) or other iterable objects. It is a way to repeat a block of code for every item in the sequence.

Syntax of a for loop

for item in iterable:
    # Code block to execute for each item

• item: A variable that iterates over the iterable (such as a list or range) and takes on the value of each element one at a time.
• iterable: An object containing multiple values (for example, a list, string, or range).
• The code block in the loop runs once for each item in the iterable.

Example 1: Iterating through a list

fruits = ["apple", "banana", "cherry"]

for fruit in fruits:
    print(fruit)

Output:

apple
banana
cherry

• Here, the loop variable fruit takes on each value in the list fruits one by one, and the print() function outputs it.

Example 2: Using range() with a for loop

The range() function generates a sequence of numbers.

for i in range(5):
    print(i)

Output:

0
1
2
3
4

• range(5) generates numbers from 0 to 4 (5 is excluded).
• The loop variable i takes these values one by one.

Example 3: Iterating through the string

text = "Jobbinge"

for char in text:
    print(char)

J
o
b
b
i
n
g
e

• The string "Jobbinge" is treated as a sequence of characters.
• The for loop processes each character one by one.
• The loop variable char takes each character of the string in order and prints it.

Example 4: Using else with a for loop

The else block in a for loop runs after the loop completes normally (without a break).

numbers = [1, 2, 3]

for num in numbers:
    print(num)
else:
    print("Loop completed.")

Output:

1
2
3
Loop completed.

Example 5: Breaking out of a loop

You can use the break statement to exit a loop prematurely.

for i in range(10):
    if i == 5:
        break
    print(i)

Output:

0
1
2
3
4

• The loop stops when i is 5.

Example 6: Skipping iterations with continue

The continue statement skips the rest of the code in the loop for the current iteration.

for i in range(5):
    if i == 2:
        continue
    print(i)

Output:

0
1
3
4

• When i is 2, the continue statement skips the print().

Common Use Cases of for loops

1. Iterating over lists, dictionaries, and tuples:

items = {"a": 1, "b": 2, "c": 3}
for key, value in items.items():
    print(f"{key}: {value}")

2. Generating a list using a loop and comprehension:

squares = [x**2 for x in range(5)]
print(squares)

3. Performing operations on each element:

numbers = [1, 2, 3, 4]
for num in numbers:
    print(num * 2)

Key Points:

• A for loop is a powerful way to process items in sequences or iterables.
• You can control the loop with break, continue, and else.
• Iterables can include not just lists, but strings, tuples, dictionaries, sets, and even custom objects.