"""

11_exceptions.py

Purpose: try/except/else/finally, raising exceptions, custom exceptions, best practices.

"""

def h(t): print("\n***", t, "***\n")

h("Try / Except basics")

try:

x = 1 / 0

except ZeroDivisionError as e:

print("Caught ZeroDivisionError:", e)

except Exception as e:

print("Generic exception:", e)

else:

print("No exception occurred")

finally:

print("This always runs")

h("Raising exceptions")

def check_age(age):

if age < 0:

raise ValueError("Age cannot be negative")

return True

try:

check_age(-5)

except ValueError as e:

print("Raised ValueError:", e)

h("Custom exceptions")

class MyAppError(Exception):

pass

def do_something(flag):

if not flag:

raise MyAppError("Flag was False")

try:

do_something(False)

except MyAppError as e:

print("Handled custom exception:", e)

h("Best practices")

# - Catch specific exceptions, not bare except.

# - Use finally for cleanup (closing files or releasing resources).

# - Add helpful messages when raising exceptions.

h("Mini Exercises")

# 1) Implement a safe division function safe_div(a,b) that returns None on error but logs the type of error.

# 2) Create a custom exception InvalidInput and use it when parsing numbers from a string fails.