For Loop

Understanding For Loops

A for loop in Python iterates over a sequence (like a list, tuple, string, or range) and executes a block of code once for each item in that sequence.

Syntax:

for variable in sequence:
    # statements

During each iteration, the variable stores the current element from the sequence.

Difference Between While and For Loops

The for loop condenses initialization, condition checking, and incrementing into a single line, making it cleaner and less error-prone.

Iterating Over Collections

Python's for loop works seamlessly with any iterable.

Example: Looping Through a List

data = [2, "Navin", 4.5, 8, "Telusko", "Muskan"]

for value in data:
    print(value)

Output

2  
Navin  
4.5  
8  
Telusko  
Muskan

Example: Looping Through a String

for ch in "PYTHON":
    print(ch)

Output:

P
Y
T
H
O
N

Example: Iterating Through a List Literal

for i in [2, 6, 'Muskan']:
    print(i)

Output:

2
6
Muskan

Using range() with For Loop

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

Example: Default range (0 to 9)

for i in range(10):
    print(i)

Output:

0
1
2
3
4
5
6
7
8
9

Example: Range with Start, Stop, and Step

for i in range(11, 21, 1):
    print(i)

Output:

11
12
13
14
15
16
17
18
19
20

Example: Reverse range

You can reverse the range using a negative step value:

for i in range(20, 10, -1):
    print(i)

Output:

20
19
18
17
16
15
14
13
12
11

Example: No Output Case

for i in range(20, 11):
    print(i)

Since the default step is +1, and the start is greater than the stop value, no output will be produced.

Using Conditions Inside For Loops

You can add conditions inside the for loop to control which items are processed.

Example 1: Skip Numbers Divisible by 5

for i in range(1, 21):
    if i % 5 == 0:
        pass
    else:
        print(i)

Output:

1
2
3
4
6
7
8
9
11
12
13
14
16
17
18
19

Example 2: Print Only Numbers Not Divisible by 5

for i in range(1, 21):
    if i % 5 != 0:
        print(i)

Output:

1
2
3
4
6
7
8
9
11
12
13
14
16
17
18
19

When to Use a Foor Loop?

Examples:

• Processing a fixed number of records
• Looping through dictionary keys and values
• Generating even numbers from 2 to 20
• Looping through large datasets safely without infinite loop risks

Summary

• A for loop iterates directly over sequences like lists, strings, tuples, sets, or ranges.
• It automatically handles indexing, increments, and stopping—simpler than a while loop.
• Works best when the number of iterations is known or when working with collections.
• The range() is commonly used to generate numeric sequences for iteration.
• Conditions inside loops allow selective processing of elements.
• It avoids infinite loops because iteration ends automatically when the sequence ends.