The for loop in Python is used to iterate over a sequence (like a list, tuple, string, or range) and execute a block of code for each item in the sequence. It’s a great tool when you know how many times you need to loop.

Syntax of a For Loop

for variable in sequence:
    # Code block to execute

• variable: Represents the current item in the sequence. The loop will assign each value from the sequence to this variable in each iteration.
• sequence: This is the collection you want to loop over (e.g., a list, string, or range).

How a For Loop Works

1. The for loop starts by taking the first item from the sequence.
2. It runs the code inside the loop using that item.
3. Then, it moves to the next item in the sequence and repeats the process.
4. When the sequence is exhausted, the loop ends.

Example 1: For Loop with a List

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

Output:

apple
banana
cherry

Explanation:

• The loop iterates over each item in the fruits list and prints it.

Example 2: For Loop with a String

word = "hello"
for letter in word:
    print(letter)

Output:

h
e
l
l
o

Explanation:

• The loop goes through each character in the string "hello" and prints it.

Example 3: For Loop with a Range

The range() function generates a sequence of numbers, which is often used with for loops.

for i in range(1, 6):
    print(i)

Output:

1
2
3
4
5

Explanation:

• The range(1, 6) generates numbers from 1 to 5 (note that 6 is excluded).

Example 4: For Loop with a Step

You can also specify a step size when using range().

for i in range(0, 10, 2):
    print(i)

Output:

0
2
4
6
8

Explanation:

• The range(0, 10, 2) generates numbers starting from 0 up to 9 with a step of 2.

Example 5: Nested For Loops

You can also have one for loop inside another. This is called a nested for loop.

for i in range(1, 4):
    for j in range(1, 4):
        print(i, j)

Output:

1 1
1 2
1 3
2 1
2 2
2 3
3 1
3 2
3 3

Explanation:

• The outer loop iterates over numbers 1 to 3.
• For each iteration of the outer loop, the inner loop also iterates over numbers 1 to 3.

Example 6: Using a For Loop with a Break Statement

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

for i in range(1, 6):
    if i == 3:
        break
    print(i)

Output:

1
2

Explanation:

• The loop stops when i equals 3, so it only prints 1 and 2.

Example 7: Using a For Loop with Continue

You can use the continue statement to skip the current iteration and move to the next.

for i in range(1, 6):
    if i == 3:
        continue
    print(i)

Output:

1
2
4
5

Explanation:

• When i equals 3, the continue statement skips that iteration, so 3 is not printed.

Key Points to Remember

1. The for loop is ideal when you know the number of iterations or are iterating over a sequence.
2. You can iterate over lists, strings, ranges, dictionaries, and other sequences.
3. Use break to exit a loop early and continue to skip to the next iteration.
4. range() is commonly used to generate numbers for looping.