Python Foundations

1. Overview

In Week 1, we usually learn printing, input, variables, datatypes, and simple calculations. In Week 2, we start making Python think. We use decisions, repetition, reusable blocks, and collections of data.

2. Week 2 learning path

This week is about moving from simple statements to structured programs.

3. Conditions: if, elif, else

Conditions allow Python to choose between different paths.

marks = 75

if marks >= 40:
    print("Pass")
else:
    print("Fail")

Multiple conditions with elif

marks = 85

if marks >= 90:
    print("Grade A+")
elif marks >= 80:
    print("Grade A")
elif marks >= 70:
    print("Grade B")
elif marks >= 60:
    print("Grade C")
elif marks >= 40:
    print("Pass")
else:
    print("Fail")

Indentation matters

Python uses indentation to understand which lines belong inside a condition.

age = 18

if age >= 18:
    print("You can vote")
    print("This line is inside the if block")

print("This line is outside the if block")

4. Logical operators

Conditions become more powerful when we combine them using logical operators.

age = 20
has_id = True

if age >= 18 and has_id:
    print("Entry allowed")
else:
    print("Entry not allowed")

Example: scholarship decision

marks = 92
attendance = 88

if marks >= 90 and attendance >= 85:
    print("Scholarship approved")
else:
    print("Scholarship not approved")

5. Loops: repeating work

Loops are used when we want to repeat something.

for loop with range

for i in range(5):
    print(i)

Output:

0
1
2
3
4

range start, stop, step

for i in range(1, 11):
    print(i)

for i in range(2, 21, 2):
    print(i)

Loop through a list

marks = [80, 75, 90, 60, 88]

for mark in marks:
    print(mark)

Loop with calculation

marks = [80, 75, 90, 60, 88]

total = 0

for mark in marks:
    total = total + mark

average = total / len(marks)

print("Total:", total)
print("Average:", average)

6. while loop

A while loop continues as long as a condition is true.

count = 1

while count <= 5:
    print(count)
    count = count + 1

Countdown example

count = 5

while count >= 1:
    print(count)
    count = count - 1

print("Start!")

Input validation example

password = ""

while password != "python123":
    password = input("Enter password: ")

print("Access granted")

7. break and continue

break stops a loop completely. continue skips the current round and moves to the next round.

break example

numbers = [10, 20, 30, 40, 50]

for number in numbers:
    if number == 30:
        break
    print(number)

Output:

10
20

continue example

numbers = [10, 20, 30, 40, 50]

for number in numbers:
    if number == 30:
        continue
    print(number)

Output:

10
20
40
50

8. Functions: reusable blocks of code

A function is a named block of code. It helps us avoid repeating the same logic.

def say_hello():
    print("Hello from Python")

say_hello()
say_hello()

Why functions are important

9. Parameters and arguments

Parameters allow a function to receive values.

def greet(name):
    print("Hello", name)

greet("Aarav")
greet("Siya")
greet("Mohan")

Function with two parameters

def add(a, b):
    print(a + b)

add(10, 20)
add(5, 7)

Marks example

def check_pass(marks):
    if marks >= 40:
        print("Pass")
    else:
        print("Fail")

check_pass(75)
check_pass(32)

10. return: sending a result back

print() displays a value. return gives a value back to the caller.

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

result = add(10, 20)
print(result)

Grade function

def find_grade(marks):
    if marks >= 90:
        return "A+"
    elif marks >= 80:
        return "A"
    elif marks >= 70:
        return "B"
    elif marks >= 60:
        return "C"
    elif marks >= 40:
        return "Pass"
    else:
        return "Fail"

grade = find_grade(86)
print("Grade:", grade)

Reusable average function

def find_average(numbers):
    total = 0

    for number in numbers:
        total = total + number

    return total / len(numbers)

marks = [80, 90, 70, 85]
average = find_average(marks)

print("Average:", average)

11. Collections: storing many values

A collection stores multiple values. Python has several important collection types.

12. Lists

A list stores multiple values in order. Lists are changeable.

marks = [80, 75, 90, 60]

print(marks)
print(marks[0])
print(marks[-1])

List methods

marks = [80, 75, 90]

marks.append(88)
print(marks)

marks.remove(75)
print(marks)

marks.sort()
print(marks)

marks.reverse()
print(marks)

Loop through list

names = ["Aarav", "Siya", "Mohan"]

for name in names:
    print("Hello", name)

List comprehension

List comprehension is a short way to create a list.

squares = []

for number in range(1, 6):
    squares.append(number * number)

print(squares)

The same work can be written like this:

squares = [number * number for number in range(1, 6)]

print(squares)

13. Tuples

A tuple is like a list, but it cannot be changed after creation.

point = (10, 20)

print(point[0])
print(point[1])

When to use tuples

• When data should not change.
• When representing fixed pairs like coordinates.
• When returning multiple values from a function.

def find_min_max(numbers):
    minimum = min(numbers)
    maximum = max(numbers)
    return minimum, maximum

result = find_min_max([10, 50, 20, 5])

print(result)
print("Minimum:", result[0])
print("Maximum:", result[1])

14. Dictionaries

A dictionary stores data as key-value pairs.

student = {
    "name": "Aarav",
    "age": 15,
    "marks": 86
}

print(student["name"])
print(student["marks"])

Add and update values

student = {
    "name": "Aarav",
    "marks": 86
}

student["city"] = "Varanasi"
student["marks"] = 90

print(student)

Loop through dictionary

student = {
    "name": "Aarav",
    "age": 15,
    "marks": 86
}

for key, value in student.items():
    print(key, "=", value)

List of dictionaries

This is very important. Real data often looks like a list of dictionaries.

students = [
    {"name": "Aarav", "marks": 86},
    {"name": "Siya", "marks": 92},
    {"name": "Mohan", "marks": 68}
]

for student in students:
    print(student["name"], student["marks"])

15. Sets

A set stores unique values. Repeated values are automatically removed.

cities = {"Varanasi", "Lucknow", "Varanasi", "Patna"}

print(cities)

Remove duplicates from a list

numbers = [10, 20, 10, 30, 20, 40]

unique_numbers = set(numbers)

print(unique_numbers)

Set operations

a = {"Python", "Java", "C"}
b = {"Python", "JavaScript", "C"}

print(a.union(b))
print(a.intersection(b))
print(a.difference(b))

16. Mini Project: Student Marks Analyzer

Now we combine conditions, loops, functions, and collections.

"""
Week 2 Mini Project
Student Marks Analyzer

Concepts used:
1. Conditions
2. Loops
3. Functions
4. Lists
5. Dictionaries
6. Reusable program structure
"""

def find_grade(marks):
    if marks >= 90:
        return "A+"
    elif marks >= 80:
        return "A"
    elif marks >= 70:
        return "B"
    elif marks >= 60:
        return "C"
    elif marks >= 40:
        return "Pass"
    else:
        return "Fail"


def find_average(marks_list):
    total = 0

    for marks in marks_list:
        total = total + marks

    return total / len(marks_list)


def print_student_report(student):
    name = student["name"]
    marks = student["marks"]

    total = sum(marks)
    average = find_average(marks)
    grade = find_grade(average)

    print("-" * 40)
    print("Name:", name)
    print("Marks:", marks)
    print("Total:", total)
    print("Average:", average)
    print("Grade:", grade)


students = [
    {"name": "Aarav", "marks": [80, 85, 90]},
    {"name": "Siya", "marks": [92, 88, 95]},
    {"name": "Mohan", "marks": [60, 68, 72]},
    {"name": "Riya", "marks": [35, 40, 38]},
    {"name": "Kabir", "marks": [75, 79, 82]}
]

print("=" * 40)
print("STUDENT MARKS ANALYZER")
print("=" * 40)

class_total = 0
highest_average = 0
topper_name = ""

for student in students:
    print_student_report(student)

    average = find_average(student["marks"])
    class_total = class_total + average

    if average > highest_average:
        highest_average = average
        topper_name = student["name"]

class_average = class_total / len(students)

print("=" * 40)
print("CLASS REPORT")
print("=" * 40)
print("Class average:", class_average)
print("Topper:", topper_name)
print("Highest average:", highest_average)

17. Full Week 2 Notebook

Copy this complete notebook into the Python editor and run it.

"""
Week 2: Python Foundations II
Programmer's Picnic by Champak Roy

Topics:
1. Conditions
2. Logical operators
3. for loops
4. while loops
5. break and continue
6. Functions
7. Parameters
8. return
9. Lists
10. Tuples
11. Dictionaries
12. Sets
13. Mini project
"""

print("=" * 60)
print("WEEK 2: PYTHON FOUNDATIONS II")
print("=" * 60)

# ------------------------------------------------------------
# 1. Conditions
# ------------------------------------------------------------

print("\n1. CONDITIONS")

marks = 85

if marks >= 90:
    print("Grade A+")
elif marks >= 80:
    print("Grade A")
elif marks >= 70:
    print("Grade B")
elif marks >= 60:
    print("Grade C")
elif marks >= 40:
    print("Pass")
else:
    print("Fail")

# ------------------------------------------------------------
# 2. Logical operators
# ------------------------------------------------------------

print("\n2. LOGICAL OPERATORS")

age = 20
has_id = True

if age >= 18 and has_id:
    print("Entry allowed")
else:
    print("Entry not allowed")

# ------------------------------------------------------------
# 3. for loop
# ------------------------------------------------------------

print("\n3. FOR LOOP")

for number in range(1, 6):
    print(number)

# ------------------------------------------------------------
# 4. Loop through list
# ------------------------------------------------------------

print("\n4. LOOP THROUGH LIST")

marks_list = [80, 75, 90, 60, 88]

total = 0

for mark in marks_list:
    total = total + mark

average = total / len(marks_list)

print("Marks:", marks_list)
print("Total:", total)
print("Average:", average)

# ------------------------------------------------------------
# 5. while loop
# ------------------------------------------------------------

print("\n5. WHILE LOOP")

count = 1

while count <= 5:
    print("Count:", count)
    count = count + 1

# ------------------------------------------------------------
# 6. break and continue
# ------------------------------------------------------------

print("\n6. BREAK AND CONTINUE")

numbers = [10, 20, 30, 40, 50]

print("Using break:")

for number in numbers:
    if number == 30:
        break
    print(number)

print("Using continue:")

for number in numbers:
    if number == 30:
        continue
    print(number)

# ------------------------------------------------------------
# 7. Functions
# ------------------------------------------------------------

print("\n7. FUNCTIONS")

def greet(name):
    print("Hello", name)

greet("Aarav")
greet("Siya")

# ------------------------------------------------------------
# 8. return
# ------------------------------------------------------------

print("\n8. RETURN")

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

result = add(10, 20)
print("Addition result:", result)

# ------------------------------------------------------------
# 9. Grade function
# ------------------------------------------------------------

print("\n9. GRADE FUNCTION")

def find_grade(marks):
    if marks >= 90:
        return "A+"
    elif marks >= 80:
        return "A"
    elif marks >= 70:
        return "B"
    elif marks >= 60:
        return "C"
    elif marks >= 40:
        return "Pass"
    else:
        return "Fail"

print("Grade for 86:", find_grade(86))
print("Grade for 35:", find_grade(35))

# ------------------------------------------------------------
# 10. Lists
# ------------------------------------------------------------

print("\n10. LISTS")

students = ["Aarav", "Siya", "Mohan"]

students.append("Riya")

for student in students:
    print(student)

# ------------------------------------------------------------
# 11. Tuples
# ------------------------------------------------------------

print("\n11. TUPLES")

point = (10, 20)

print("X:", point[0])
print("Y:", point[1])

# ------------------------------------------------------------
# 12. Dictionaries
# ------------------------------------------------------------

print("\n12. DICTIONARIES")

student = {
    "name": "Aarav",
    "age": 15,
    "marks": 86
}

for key, value in student.items():
    print(key, "=", value)

# ------------------------------------------------------------
# 13. Sets
# ------------------------------------------------------------

print("\n13. SETS")

cities = ["Varanasi", "Lucknow", "Varanasi", "Patna", "Lucknow"]

unique_cities = set(cities)

print("Original cities:", cities)
print("Unique cities:", unique_cities)

# ------------------------------------------------------------
# 14. Mini project
# ------------------------------------------------------------

print("\n14. MINI PROJECT: STUDENT MARKS ANALYZER")

def find_average(marks):
    total = 0

    for mark in marks:
        total = total + mark

    return total / len(marks)


def print_student_report(student):
    name = student["name"]
    marks = student["marks"]

    total = sum(marks)
    average = find_average(marks)
    grade = find_grade(average)

    print("-" * 40)
    print("Name:", name)
    print("Marks:", marks)
    print("Total:", total)
    print("Average:", average)
    print("Grade:", grade)


students_data = [
    {"name": "Aarav", "marks": [80, 85, 90]},
    {"name": "Siya", "marks": [92, 88, 95]},
    {"name": "Mohan", "marks": [60, 68, 72]},
    {"name": "Riya", "marks": [35, 40, 38]},
    {"name": "Kabir", "marks": [75, 79, 82]}
]

class_total = 0
highest_average = 0
topper_name = ""

for student in students_data:
    print_student_report(student)

    average = find_average(student["marks"])
    class_total = class_total + average

    if average > highest_average:
        highest_average = average
        topper_name = student["name"]

class_average = class_total / len(students_data)

print("=" * 40)
print("CLASS REPORT")
print("=" * 40)
print("Class average:", class_average)
print("Topper:", topper_name)
print("Highest average:", highest_average)

print("\n" + "=" * 60)
print("WEEK 2 NOTEBOOK COMPLETE")
print("=" * 60)

18. Python Editor

Run the Week 2 notebook here. Change marks, names, conditions, and functions. Observe how the output changes.

19. Practice tasks

# 1. Conditions

marks = int(input("Enter marks: "))

if marks >= 40:
    print("Pass")
else:
    print("Fail")


# 2. Grade calculator

marks = int(input("Enter marks: "))

if marks >= 90:
    print("A+")
elif marks >= 80:
    print("A")
elif marks >= 70:
    print("B")
elif marks >= 60:
    print("C")
elif marks >= 40:
    print("Pass")
else:
    print("Fail")


# 3. Multiplication table

for i in range(1, 11):
    print("7 x", i, "=", 7 * i)


# 4. while loop countdown

count = 10

while count >= 1:
    print(count)
    count = count - 1


# 5. Function

def square(number):
    return number * number

print(square(5))


# 6. List total and average

marks = [80, 90, 70, 85, 95]

total = 0

for mark in marks:
    total = total + mark

average = total / len(marks)

print("Total:", total)
print("Average:", average)


# 7. Dictionary

student = {
    "name": "Aarav",
    "age": 15,
    "city": "Varanasi",
    "marks": 86
}

for key, value in student.items():
    print(key, "=", value)


# 8. Set

cities = ["Varanasi", "Lucknow", "Varanasi", "Patna", "Lucknow"]

unique_cities = set(cities)

print(unique_cities)

20. Final challenge

Create a library book tracker using Week 2 concepts.

Your program should use:

• A list of dictionaries to store books.
• Each book should have title, author, price, and availability.
• A function to print all books.
• A function to find expensive books.
• A function to count available books.
• Conditions to check availability.
• Loops to process all books.

books = [
    {"title": "Python Basics", "author": "A", "price": 300, "available": True},
    {"title": "Data Science", "author": "B", "price": 650, "available": False},
    {"title": "Machine Learning", "author": "C", "price": 800, "available": True},
    {"title": "Web Development", "author": "D", "price": 450, "available": True}
]

# Write your functions below

books = [
    {"title": "Python Basics", "author": "A", "price": 300, "available": True},
    {"title": "Data Science", "author": "B", "price": 650, "available": False},
    {"title": "Machine Learning", "author": "C", "price": 800, "available": True},
    {"title": "Web Development", "author": "D", "price": 450, "available": True}
]

def print_all_books(books):
    for book in books:
        print("-" * 40)
        print("Title:", book["title"])
        print("Author:", book["author"])
        print("Price:", book["price"])

        if book["available"]:
            print("Status: Available")
        else:
            print("Status: Not available")


def print_expensive_books(books, limit):
    print("Books above", limit)

    for book in books:
        if book["price"] > limit:
            print(book["title"], "-", book["price"])


def count_available_books(books):
    count = 0

    for book in books:
        if book["available"]:
            count = count + 1

    return count


print_all_books(books)
print_expensive_books(books, 500)

available_count = count_available_books(books)

print("Available books:", available_count)

21. What you now know