class AgeLimitError(Exception):
    def __init__(self, age):
        super().__init__(f"Age {age} is below allowed limit")

def validate_age(age):
    if age < 18:
        raise AgeLimitError(age)

validate_age(15)

nested = [[1, 2], [3, 4], [5]]
flat = [item for sublist in nested for item in sublist]

def add(a, b, c=0):
    return a + b + c

print(add(2, 3))        # 5
print(add(2, 3, 4))     # 9

5
9

import csv

records = [
    {"name": "Alice", "age": 25, "city": "Rome"},
    {"name": "Bob", "age": 30, "city": "Madrid"}
]

with open("records.csv", "w", newline="") as file:
    writer = csv.DictWriter(file, fieldnames=records[0].keys())
    writer.writeheader()
    writer.writerows(records)

import os

current_dir = os.getcwd()
print(current_dir)

C:\Users\Ashwin\kact\pynotes\notebooks\basics

x = 100

def outer():
    def inner():
        global x
        x = 400

    inner()

outer()
print(x)  

400

status = "inactive"

def activate():
    global status
    status = "active"

def show_status():
    print(status)

activate()
show_status()  # Output: active

active

mode = "light"

def toggle_mode():
    global mode
    if mode == "light":
        mode = "dark"
    else:
        mode = "light"

toggle_mode()
print(mode)  # Output: dark

dark

x = 100

def show():
    print(x)