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:

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:

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:

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

Common Use Cases of `for` loops

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.