While Loop, break, continue, Functions, Modularization & Modules In Python

The day Python stopped being a notebook and became a real multi-file project — run from the terminal.

Part 1 — while Loop

A for loop runs a fixed number of times. A while loop runs as long as a condition is True. You control when it stops.

while condition:
    # statement
    counter update (i++)    ← CRITICAL — without this, infinite loop!

Example 1 — Count 0 to 11

count = 0

while count <= 11:
    print(count)
    count += 1        

# Output:
# 0  1  2  3  4  5  6  7  8  9  10  11

Three things every while loop needs:

Initialize the counter before the loop (count = 0)

Condition that will eventually become False (count <= 11)

Update the counter inside the loop (count += 1)

Miss the third one — your loop runs forever. That’s called an infinite loop.

Example 2 — Multiplication Table with while

num = int(input("Enter any number: "))   # input() — Day 3
i = 1

while i <= 10:
    print(f"{num} x {i} = {num * i}")    # f-string — Day 3
    i += 1

# Input: 10
# 10 x 1 = 10
# 10 x 2 = 20
# 10 x 3 = 30
# ...
# 10 x 10 = 100

for vs while — When to Use Which?

## break and continue

break and continue

These two keywords give you control inside a loop.

break    →  exits the loop immediately (prematurely)
continue →  skips current iteration and goes to the next one

Example 3 — break exits immediately

for i in range(0, 10):
    print(i)
    break             # exits after first iteration

# Output: 0

The loop would normally run 10 times. break stops it after the very first step.

Example 4 — continue skips one iteration

for i in range(0, 10):
    if i == 5:
        continue      # skip 5, go to next iteration
    print(i)

# Output: 0  1  2  3  4  6  7  8  9
#         ↑ notice 5 is missing

Example 5 — Find First Even Number ≤ 50 in a List

numbers = [3, 7, 52, 45, 67, 8, 34, 2]

for num in numbers:
    if num % 2 == 0 and num <= 50:   
        print(num)
        break                         # stop as soon as we find it

# Output: 8

Walks through the list one by one. The moment it finds a number that is both even and ≤ 50 — it prints it and stops immediately.

Example 6 — Print Only Even Numbers from a List (using continue)

numbers = [3, 7, 52, 45, 67, 8, 34, 2]

for num in numbers:
    if num % 2 != 0:      # if odd
        continue          # skip odd numbers
    if num <= 50:
        print(num)
        break

# Output: 8

`continue` skips any odd number. `break` stops after finding the first qualifying even number.

Modularization → Making multiple modules

Benefits:

Reusability — write once, use across different programs

Maintainability — smaller, independent pieces are easier to fix

Scalability — easy to add new modules without breaking others

Organization — keeps code clean and manageable

Functions

A function is a named, reusable block of code that performs a specific task.

def functionName(parameters):
    statement
    return value

def — keyword to define a function

functionName — what you call it

parameters — inputs it receives

return — what it gives back

# defining the function
def addition(a, b):
    return a + b

# calling the function
x = addition(2, 8)
print(x)             # 10

### The Folder Structure

project/
├── main.py          ← runs everything
├── example.py       ← contains addition()
├── day8.ipynb       ← Jupyter notebook
└── mod/
    └── example2.py  ← contains suntract() and multiple()

example.py — The First Module

def addition(a, b):
    return a + b

mod/example2.py — The Second Module (inside a folder)

def suntract(a, b):
    return a - b

def multiple(a, b):
    return a * b

main.py — The Entry Point

from example import addition            # import from example.py
from mod.example2 import *             # import everything from mod/example2.py

x = addition(10, 5)                    # uses addition() from example.py
y = suntract(4, 2)                     # uses suntract() from mod/example2.py
z = multiple(2, 3)                     # uses multiple() from mod/example2.py

print(f"x={x}, y ={y}, z = {z}")

# Output: x=15, y =2, z = 6

Running from Anaconda Prompt

This is the moment the project became real.

# Navigate to the folder where your main.py file is saved
# Then run the script using the Anaconda Prompt command below:

python main.py

x=15, y =2, z = 6

Three Ways to Import

# Method 1: Basic import — use full path to call
import example
a = example.addition(4, 5)      

# Method 2: Full module path — verbose, not ideal
import mod.example2
z = mod.example2.addition(4, 8)  # → works but long

# Method 3: Selective import — clean and specific ✅
from mod.example2 import suntract, multiple
x = suntract(9, 1)              
y = multiple(5, 3)              

# Method 4: Import everything — use with care
from mod.example2 import *