Loops for Beginners (with python code)

 

Understanding Loops in Python

Loops are a fundamental concept in programming that allow us to repeat a block of code multiple times. They are useful for tasks that involve repetitive actions.

1. Main Points About Loops

• For Loop: Used to iterate over a sequence (such as a list, tuple, dictionary, set, or string) and execute a block of code for each item in the sequence.
• While Loop: Repeats a block of code as long as a specified condition is true.
• Break Statement: Exits the loop prematurely if a certain condition is met.
• Continue Statement: Skips the current iteration and moves to the next iteration of the loop.

2. Creating a Math Table Using a Simple For Loop

Let's create a simple math table using a for loop in Python. This example will print the multiplication table for the number 5.

Python Code

    
    # Multiplication table for number 5
    num = 5
    for i in range(1, 11):
        print(num * i)
    
    

Output

    
    5
    10
    15
    20
    25
    30
    35
    40
    45
    50
    
    

Explanation

The code uses a for loop to iterate through numbers 1 to 10. For each iteration, it multiplies the number 5 by the current iteration number (i) and prints the result.

Box Diagram

    
    +-------------------------+
    | num = 5                 |
    +-------------------------+
    | for i in range(1, 11):  |
    |     +-------------------+
    |     | print(num * i)    |
    +-------------------------+
    
    

3. Creating Math Tables from 1 to 10 Using Nested Loops

Now let's create math tables from 1 to 10 using nested loops. This example will generate a 10x10 table of multiplication results.

Python Code

    
    # Multiplication tables from 1 to 10
    for i in range(1, 11):
        for j in range(1, 11):
            print(i * j, end=' ')
        print()
    
    

Output

    
    1 2 3 4 5 6 7 8 9 10 
    2 4 6 8 10 12 14 16 18 20 
    3 6 9 12 15 18 21 24 27 30 
    4 8 12 16 20 24 28 32 36 40 
    5 10 15 20 25 30 35 40 45 50 
    6 12 18 24 30 36 42 48 54 60 
    7 14 21 28 35 42 49 56 63 70 
    8 16 24 32 40 48 56 64 72 80 
    9 18 27 36 45 54 63 72 81 90 
    10 20 30 40 50 60 70 80 90 100 
    
    

Explanation

The code uses two nested for loops. The outer loop iterates through numbers 1 to 10 (i), and the inner loop iterates through numbers 1 to 10 (j). For each combination of i and j, it multiplies the two numbers and prints the result. The end=' ' parameter in the print function ensures that the results are printed on the same line, and the inner loop prints a newline character after each inner loop completes.

Box Diagram

    
    +------------------------------+
    | for i in range(1, 11):       |
    |     +------------------------+
    |     | for j in range(1, 11): |
    |     |     +------------------+
    |     |     | print(i * j, end=' ') |
    |     +------------------------+
    |     | print()               |
    +------------------------------+
    
    

4. Looping Through Lists and Dictionaries

Loops are also useful for iterating through lists and dictionaries. Here are examples of how to loop through these data structures.

Looping Through a List

Let's loop through a list of numbers and print each number.

Python Code

    
    numbers = [1, 2, 3, 4, 5]
    for num in numbers:
        print(num)
    
    

Output

    
    1
    2
    3
    4
    5
    
    

Box Diagram

    
    +---------------------+
    | numbers = [1, 2, 3, 4, 5] |
    +---------------------+
    | for num in numbers: |
    |     +---------------+
    |     | print(num)    |
    +---------------------+
    
    

Looping Through a Dictionary

Let's loop through a dictionary and print each key-value pair.

Python Code

    
    student_scores = {"Alice": 85, "Bob": 92, "Charlie": 78}
    for student, score in student_scores.items():
        print(student, score)
    
    

Output

    
    Alice 85
    Bob 92
    Charlie 78
    
    

Box Diagram

    
    +--------------------------------------+
    | student_scores = {"Alice": 85, "Bob": 92, "Charlie": 78} |
    +--------------------------------------+
    | for student, score in student_scores.items(): |
    |     +----------------------------------------+
    |     | print(student, score)                  |
    +--------------------------------------+

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