24_basic_functions.py

#======================================================================================
#                               Functions
#--------------------------------------------------------------------------------------
# A function is a reusable block of code that performs a specific task
# Why use functions ?
#   Code reusability
#   Better organization
#   Easier debugging
#   Reduces repetition
#======================================================================================
import math
#--------------------------------------------------------------------------------------
# Built-in Function (Just Calling)
#--------------------------------------------------------------------------------------
print(len('python'))

#--------------------------------------------------------------------------------------
# Function From Libraries (Import Then Call)
#--------------------------------------------------------------------------------------
number = 4.2
print(math.ceil(number))


#--------------------------------------------------------------------------------------
# User Defined Function
#--------------------------------------------------------------------------------------
# Defining a Function
def greet():
    print(f'Hello World')

# Calling a Function
greet()

#--------------------------------------------------------------------------------------
# Function components
#--------------------------------------------------------------------------------------
#   def     --> keyword used to create a function
#   greet   --> function name
#   ()      --> parameter area
#   :       --> starts function body
#   Indented code   -->function body
#--------------------------------------------------------------------------------------

# Here we are using parameters and arguments in functions
# Check 25_parameters_&_arguments.py file for more about parameters and arguments 
#--------------------------------------------------------------------------------------
# return --> sends a value back from a function
#--------------------------------------------------------------------------------------
# syntax
# def function_name():
#   return value
#--------------------------------------------------------------------------------------
# Returning a sum
def add(a,b):
    return a + b
result = add(10,20)
print(result)

#--------------------------------------------------------------------------------------
# Key Point:- If a function has no return statement, python returns None by default
#--------------------------------------------------------------------------------------

def add1(x,y):
    print(x+y)

result = add1(5,5)
print(result)

#--------------------------------------------------------------------------------------
# Important Points
#--------------------------------------------------------------------------------------
# return ends the function immediately.
# A function can have multiple return statements:
# Code after return inside the same block will not execute.
#--------------------------------------------------------------------------------------

# return ends the function immediately.
def demo():
    return 'Hello'
    print('World')  # Never runs
result = demo()
print(result)


# A function can have multiple return statements:
# Code after return inside the same block will not execute.
def clean_name(name):
    if not name:
        return None
    else:
        return name.strip().lower()

result1 = clean_name('')
print(result1)

result2 = clean_name('  MaRIA   ')
print(result2)

# Returning multiple values
def clean_name(name):
    lo_cleaned = name.strip().lower()
    up_cleaned = name.strip().upper()
    return lo_cleaned, up_cleaned

lo_name, up_name = clean_name('  aLeX   ')
print(lo_name)
print(up_name)