Functions

On This Page

• 7.1  Function Basics
• 7.2  Parameters & Arguments
• 7.3  The return Statement
• 7.4  Default Parameters
• 7.5  Keyword Arguments
• 7.6  Lambda Functions
• 7.7  Recursion
• 7.8  Scope (Local vs Global)
• 7.9  Mini Project — Fee Calculator Toolkit
• 7.10  Practical Exercises
• 7.11  Module Quiz (MCQs)
• 7.12  Module Assignment
• 7.13  Interview Questions — Module 7
• 7.14  Student Notes Page

Module 7: Functions

7.1  Function Basics

A function is a reusable block of code that performs a specific task. Instead of writing the same code again and again, you define it once and simply 'call' it whenever needed.

def greet_student():
    print("Welcome to Samantus Web Training Institute!")

greet_student()   # calling the function
greet_student()   # can be called as many times as needed

7.2  Parameters & Arguments

Parameters are placeholders defined in the function itself; arguments are the actual values you pass in when calling the function.

def greet(name):          # "name" is the parameter
    print(f"Hello, {name}! Welcome to Samantus.")

greet("Priya")            # "Priya" is the argument
greet("Rahul")

7.3  The return Statement

The return statement sends a value back from the function to wherever it was called — unlike print(), which only displays and does not give back a usable value.

def calculate_gst(price):
    gst = price * 0.18
    return price + gst

final_price = calculate_gst(1000)
print("Final Price:", final_price)

7.4  Default Parameters

You can give a parameter a default value, which is used automatically if the caller doesn't provide one.

def enroll_student(name, course="Digital Marketing"):
    print(f"{name} enrolled in {course}")

enroll_student("Anita")                 # uses default course
enroll_student("Vikram", "SEO")         # overrides default

7.5  Keyword Arguments

Keyword arguments let you pass values by explicitly naming the parameter, so order doesn't matter.

def student_info(name, age, course):
    print(f"{name}, Age {age}, Course: {course}")

# Using keyword arguments - order does not matter here
student_info(age=24, course="Google Ads", name="Meena")

7.6  Lambda Functions

A lambda function is a small, anonymous, one-line function — useful for short operations where defining a full function feels unnecessary.

square = lambda x: x * x
print(square(5))

add = lambda a, b: a + b
print(add(10, 20))

# Common use: sorting a list of tuples by the second value
students = [("Raj", 85), ("Meena", 92), ("Amit", 78)]
students.sort(key=lambda s: s[1], reverse=True)
print(students)

7.7  Recursion

Recursion is when a function calls itself to solve a smaller version of the same problem, until it reaches a stopping point called the base case.

def factorial(n):
    if n == 0 or n == 1:      # base case - stops the recursion
        return 1
    return n * factorial(n - 1)   # recursive call

print(factorial(5))   # 5*4*3*2*1

7.8  Scope (Local vs Global)

Scope determines where a variable can be accessed. A local variable exists only inside the function where it's created; a global variable exists throughout the program.

institute_name = "Samantus"   # global variable

def show_info():
    course = "SEO"            # local variable
    print(institute_name, "-", course)   # can read global here

show_info()
# print(course)   # This would cause an ERROR - course is local only

7.9  Mini Project — Fee Calculator Toolkit

Build a small toolkit of functions that could be used in a real training institute's billing system.

def calculate_gst(amount, rate=0.18):
    return round(amount * rate, 2)

def apply_discount(amount, discount_percent=0):
    return round(amount - (amount * discount_percent / 100), 2)

def final_fee(base_fee, discount_percent=0):
    discounted = apply_discount(base_fee, discount_percent)
    gst = calculate_gst(discounted)
    return discounted + gst

print("Final Fee:", final_fee(15000, discount_percent=10))

7.10  Practical Exercises

Basic (5 Questions)

1. Write a function that prints your name and course.

2. Write a function that takes a number and returns its square.

3. Write a function with a default parameter for 'city' set to 'Delhi'.

4. Write a function to add two numbers and return the result.

5. Write a lambda function to double a number.

Intermediate (5 Questions)

1. Write a function to check if a number is prime and return True/False.

2. Write a function using keyword arguments to build a student profile.

3. Write a recursive function to calculate the sum of numbers from 1 to n.

4. Write a function that returns the maximum of 3 numbers without using max().

5. Demonstrate local vs global scope with your own example (not from the notes).

Advanced (5 Questions)

1. Write a recursive function to calculate the Fibonacci number at position n.

2. Build a function-based 'Simple Interest Calculator' with principal, rate, and time as parameters (rate has a default value).

3. Use lambda with sorted() to sort a list of dictionaries by a specific key.

4. Write a function that takes any number of arguments using *args and returns their sum.

5. Build a small toolkit of 3 functions for a 'Marks Analyzer' (average, highest, grade) and combine them in one function.

7.11  Module Quiz (MCQs)

7.12  Module Assignment

Assignment: Build a Student Fee Management Toolkit

• Write a function calculate_total(base_fee, discount, gst_rate=0.18) that returns the final payable fee.
• Write a separate function is_eligible_for_discount(course_count) that returns True if a student enrolls in 2+ courses.
• Write a recursive function to calculate total fee for n installments (equal monthly amounts).
• Combine all three functions into one script and test with sample data.

Expected Output: A working, modular fee-management script where each function performs one clear job and can be reused independently.

7.13  Interview Questions — Module 7

• Q: What is the difference between a parameter and an argument?
  A: A parameter is the variable name listed in the function definition, while an argument is the actual value passed in when the function is called.
• Q: What is the difference between print() and return in a function?
  A: print() only displays output on screen, while return sends a value back to the caller so it can be stored or used further in the program.
• Q: What is recursion, and what risk does it carry?
  A: Recursion is a function calling itself to solve smaller sub-problems; without a proper base case, it can cause a RecursionError from infinite self-calls.
• Q: What is variable scope?
  A: Scope defines where a variable can be accessed — local variables exist only inside their function, while global variables are accessible throughout the program.

7.14  Student Notes Page

Use this space to write down key points, doubts, and your own examples from today's session.