Python Sample Programs
Learn by Example

print("Hello, World!")

print("Hello", "World", "from", "Python")

name = "Alice"
age = 25
height = 5.8
is_student = True

print(f"Name: {name}, Type: {type(name)}")
print(f"Age: {age}, Type: {type(age)}")
print(f"Height: {height}, Type: {type(height)}")
print(f"Student: {is_student}, Type: {type(is_student)}")

name = input("What's your name? ")
age = input("How old are you? ")

age = int(age)

print(f"Hello {name}! You are {age} years old.")
print(f"Next year you'll be {age + 1}.")

a = 10
b = 3

print(f"a = {a}, b = {b}")
print(f"a + b = {a + b}")
print(f"a - b = {a - b}")
print(f"a * b = {a * b}")
print(f"a / b = {a / b}")
print(f"a // b = {a // b} (floor division)")
print(f"a % b = {a % b} (remainder)")
print(f"a ** b = {a ** b} (exponent)")

fruits = ["apple", "banana", "cherry", "date"]
print("Original:", fruits)

print("First:", fruits[0])
print("Last:", fruits[-1])

fruits.append("elderberry")
fruits.insert(1, "blueberry")
print("After adding:", fruits)

fruits.remove("banana")
last = fruits.pop()
print("After removing:", fruits)
print("Popped:", last)

print("First three:", fruits[:3])
print("Reversed:", fruits[::-1])

for fruit in fruits:
    print(fruit, end=" ")

person = {
    "name": "Alice",
    "age": 30,
    "city": "New York",
    "skills": ["Python", "Data Science"]
}

print("Name:", person["name"])
print("Age:", person.get("age"))
print("City:", person.get("country", "Unknown"))

person["country"] = "USA"
person["age"] = 31
print("Updated:", person)

for key, value in person.items():
    print(f"{key}: {value}")

if "skills" in person:
    print("Skills:", person["skills"])

point = (3, 4)
rgb = (255, 128, 0)
person = ("Alice", 30, "NYC")

print("Point:", point)
print("x:", point[0], "y:", point[1])

x, y = point
name, age, city = person
print(f"x={x}, y={y}")
print(f"{name} is {age} years old from {city}")

grid = {}
grid[(0, 0)] = "origin"
grid[(1, 2)] = "point"
print("Grid:", grid)

set_a = {1, 2, 3, 4, 5}
set_b = {4, 5, 6, 7, 8}

print("Set A:", set_a)
print("Set B:", set_b)

print("Union:", set_a | set_b)
print("Intersection:", set_a & set_b)
print("Difference (A - B):", set_a - set_b)
print("Symmetric Difference:", set_a ^ set_b)

set_a.add(6)
set_a.discard(1)
print("Modified A:", set_a)

numbers = [1, 2, 2, 3, 3, 3, 4, 5, 5]
unique = list(set(numbers))
print("Original:", numbers)
print("Unique:", unique)

num = int(input("Enter a number: "))

if num > 0:
    print("The number is positive")
elif num < 0:
    print("The number is negative")
else:
    print("The number is zero")

score = int(input("Enter score (0-100): "))

if score >= 90:
    grade = "A"
elif score >= 80:
    grade = "B"
elif score >= 70:
    grade = "C"
elif score >= 60:
    grade = "D"
else:
    grade = "F"

print(f"Grade: {grade}")

fruits = ["apple", "banana", "cherry"]
for fruit in fruits:
    print(f"I like {fruit}")

for i, fruit in enumerate(fruits):
    print(f"{i}: {fruit}")

for i in range(5):
    print(i, end=" ")
print()

for i in range(2, 10, 2):
    print(i, end=" ")
print()

for i in range(3):
    for j in range(2):
        print(f"({i},{j})", end=" ")
    print()

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

total = 0
num = int(input("Enter number (0 to stop): "))
while num != 0:
    total += num
    num = int(input("Enter number (0 to stop): "))
print(f"Sum: {total}")

print("Counting...")
n = 0
while True:
    n += 1
    if n > 5:
        break
    print(n, end=" ")

n = 5
for i in range(1, n + 1):
    print("*" * i)

print()

for i in range(n, 0, -1):
    print("*" * i)

print()

for i in range(1, n + 1):
    spaces = " " * (n - i)
    stars = "*" * (2 * i - 1)
    print(spaces + stars)

for i in range(1, 6):
    for j in range(1, i + 1):
        print(j, end=" ")
    print()

def greet(name):
    return f"Hello, {name}!"

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

def is_even(n):
    return n % 2 == 0

print(greet("Alice"))
print("5 + 3 =", add(5, 3))
print("Is 10 even?", is_even(10))
print("Is 7 even?", is_even(7))

def power(base, exponent=2):
    return base ** exponent

print("3^2 =", power(3))
print("2^5 =", power(2, 5))

def min_max(numbers):
    return min(numbers), max(numbers)

min_val, max_val = min_max([3, 1, 4, 1, 5, 9])
print("Min:", min_val, "Max:", max_val)

def factorial(n):
    if n <= 1:
        return 1
    return n * factorial(n - 1)

print("5! =", factorial(5))
print("10! =", factorial(10))

def fibonacci(n):
    if n <= 1:
        return n
    return fibonacci(n - 1) + fibonacci(n - 2)

for i in range(10):
    print(fibonacci(i), end=" ")

print()

def sum_list(lst):
    if not lst:
        return 0
    return lst[0] + sum_list(lst[1:])

print("Sum [1,2,3,4] =", sum_list([1, 2, 3, 4]))

square = lambda x: x ** 2
print("Square of 5:", square(5))

numbers = [1, 2, 3, 4, 5]
squared = list(map(lambda x: x ** 2, numbers))
print("Squared:", squared)

evens = list(filter(lambda x: x % 2 == 0, numbers))
print("Evens:", evens)

words = ["apple", "banana", "cherry", "date"]
sorted_words = sorted(words, key=lambda w: len(w))
print("Sorted by length:", sorted_words)

from functools import reduce
product = reduce(lambda a, b: a * b, numbers)
print("Product:", product)

class Car:
    def __init__(self, make, model, year):
        self.make = make
        self.model = model
        self.year = year
        self.mileage = 0

    def drive(self, miles):
        self.mileage += miles
        return f"Driven {miles} miles. Total: {self.mileage}"

    def display(self):
        return f"{self.year} {self.make} {self.model}, Mileage: {self.mileage}"

car1 = Car("Toyota", "Camry", 2020)
car2 = Car("Honda", "Civic", 2022)

print(car1.display())
print(car2.display())
print(car1.drive(150))
print(car1.display())

class Animal:
    def __init__(self, name):
        self.name = name

    def speak(self):
        return "Some sound"

class Dog(Animal):
    def speak(self):
        return "Woof!"

class Cat(Animal):
    def speak(self):
        return "Meow!"

class Bird(Animal):
    def __init__(self, name, can_fly):
        super().__init__(name)
        self.can_fly = can_fly

    def speak(self):
        return "Chirp!"

animals = [Dog("Buddy"), Cat("Whiskers"), Bird("Tweety", True)]

for animal in animals:
    print(f"{animal.name} says: {animal.speak()}")
    if isinstance(animal, Bird):
        print(f"Can fly: {animal.can_fly}")

class BankAccount:
    def __init__(self, owner, balance=0):
        self.owner = owner
        self._balance = balance

    @property
    def balance(self):
        return self._balance

    @balance.setter
    def balance(self, value):
        if value < 0:
            raise ValueError("Balance cannot be negative")
        self._balance = value

    def deposit(self, amount):
        if amount <= 0:
            raise ValueError("Amount must be positive")
        self._balance += amount

    def withdraw(self, amount):
        if amount > self._balance:
            raise ValueError("Insufficient funds")
        self._balance -= amount

account = BankAccount("Alice", 1000)
print(f"Balance: ${account.balance}")
account.deposit(500)
print(f"After deposit: ${account.balance}")
account.withdraw(200)
print(f"After withdrawal: ${account.balance}")

text = "  Hello, World!  "

print("Strip:", text.strip())

print("Lower:", text.lower())
print("Upper:", text.upper())
print("Title:", text.title())

words = text.strip().split(", ")
print("Split:", words)
joined = "|".join(words)
print("Join:", joined)

replaced = text.replace("World", "Python")
print("Replace:", replaced)

print("Find 'World':", text.find("World"))
print("Count 'l':", text.count("l"))

print("Starts with 'Hello':", text.strip().startswith("Hello"))
print("Ends with '!':", text.strip().endswith("!"))

def is_palindrome(text):
    text = text.lower().replace(" ", "")
    return text == text[::-1]

words = ["racecar", "A man a plan a canal Panama", "hello", "never odd or even"]

for word in words:
    result = is_palindrome(word)
    print(f"'{word}' → {result}")

from collections import Counter

text = "Python is amazing. Python is fun. Python is the best language."

words = text.lower().split()
word_counts = Counter(words)

for word, count in word_counts.most_common():
    print(f"{word}: {count}")

counts = {}
for word in words:
    counts[word] = counts.get(word, 0) + 1

print("Manual count:", counts)

import math

def is_prime(n):
    if n < 2:
        return False
    for i in range(2, int(math.sqrt(n)) + 1):
        if n % i == 0:
            return False
    return True

test_numbers = [1, 2, 3, 4, 17, 18, 97, 100]
for n in test_numbers:
    print(f"{n}: {is_prime(n)}")

primes = [n for n in range(50) if is_prime(n)]
print("Primes up to 50:", primes)

def fibonacci_iter(n):
    if n <= 0:
        return []
    elif n == 1:
        return [0]
    elif n == 2:
        return [0, 1]
    
    seq = [0, 1]
    for i in range(2, n):
        seq.append(seq[-1] + seq[-2])
    return seq

def fibonacci_gen(n):
    a, b = 0, 1
    for _ in range(n):
        yield a
        a, b = b, a + b

print("Fibonacci (iterative):", fibonacci_iter(10))
print("Fibonacci (generator):", list(fibonacci_gen(10)))

fibo = fibonacci_iter(50)
print("50th Fibonacci:", fibo[-1])

from statistics import mean, median, mode, stdev

data = [10, 12, 14, 16, 18, 18, 20, 22, 24, 26, 28, 30, 30, 30]

print("Data:", data)
print("Count:", len(data))
print("Mean:", mean(data))
print("Median:", median(data))
print("Mode:", mode(data))
print("Standard Deviation:", stdev(data))
print("Min:", min(data))
print("Max:", max(data))
print("Sum:", sum(data))

print("Manual mean:", sum(data) / len(data))

import math

a, b = 48, 18

print("GCD (math):", math.gcd(a, b))
print("LCM (math):", abs(a * b) // math.gcd(a, b))

def gcd_euclidean(a, b):
    while b:
        a, b = b, a % b
    return a

def lcm(a, b):
    return abs(a * b) // gcd_euclidean(a, b)

print("GCD (Euclidean):", gcd_euclidean(a, b))
print("LCM:", lcm(a, b))

numbers = [24, 36, 48, 60]
result = numbers[0]
for n in numbers[1:]:
    result = math.gcd(result, n)
print("GCD of", numbers, "=", result)

with open("sample.txt", "w", encoding="utf-8") as f:
    f.write("Hello, file!\n")
    f.write("This is line two.\n")
    f.write("Python makes file handling easy.\n")

with open("sample.txt", "r", encoding="utf-8") as f:
    content = f.read()
    print("File content:")
    print(content)

with open("sample.txt", "r", encoding="utf-8") as f:
    print("Lines:")
    for line in f:
        print(f"  {line.strip()}")

with open("sample.txt", "a", encoding="utf-8") as f:
    f.write("This line is appended.\n")

import csv

data = [
    ["Name", "Age", "City"],
    ["Alice", 25, "NYC"],
    ["Bob", 30, "LA"],
    ["Charlie", 35, "Chicago"]
]

with open("people.csv", "w", newline="", encoding="utf-8") as f:
    writer = csv.writer(f)
    writer.writerows(data)

with open("people.csv", "r", encoding="utf-8") as f:
    reader = csv.reader(f)
    for row in reader:
        print(row)

with open("people.csv", "r", encoding="utf-8") as f:
    reader = csv.DictReader(f)
    for row in reader:
        print(f"{row['Name']} is {row['Age']} years old from {row['City']}")

import functools, time

def timer(func):
    @functools.wraps(func)
    def wrapper(*args, **kwargs):
        start = time.perf_counter()
        result = func(*args, **kwargs)
        elapsed = time.perf_counter() - start
        print(f"{func.__name__} took {elapsed:.4f} seconds")
        return result
    return wrapper

def log(func):
    @functools.wraps(func)
    def wrapper(*args, **kwargs):
        print(f"Calling {func.__name__} with args={args}, kwargs={kwargs}")
        result = func(*args, **kwargs)
        print(f"{func.__name__} returned {result}")
        return result
    return wrapper

@timer
def slow_function():
    time.sleep(0.5)
    return "Done"

@log
@timer
def add(a, b):
    return a + b

print(slow_function())
print(add(3, 4))

def squares(n):
    for i in range(n):
        yield i ** 2

for sq in squares(5):
    print(sq, end=" ")
print()

list_comp = [x**2 for x in range(5)]
gen_exp = (x**2 for x in range(5))

print("List comprehension:", list_comp)
print("Generator expression:", list(gen_exp))

def read_large_file(filename):
    with open(filename, "r", encoding="utf-8") as f:
        for line in f:
            yield line.strip()

for line in read_large_file("sample.txt"):
    print("Line:", line)

squares = [x**2 for x in range(10)]
print("Squares:", squares)

evens = [x for x in range(20) if x % 2 == 0]
print("Evens:", evens)

matrix = [[i * j for j in range(1, 4)] for i in range(1, 4)]
for row in matrix:
    print(row)

nested = [[1, 2], [3, 4, 5], [6, 7]]
flattened = [item for sublist in nested for item in sublist]
print("Flattened:", flattened)

pairs = [(1, "one"), (2, "two"), (3, "three")]
dict_comp = {k: v for k, v in pairs}
print("Dictionary:", dict_comp)

set_comp = {x**2 for x in [1, 2, 2, 3, 3, 3]}
print("Set:", set_comp)

def safe_divide(a, b):
    try:
        result = a / b
    except ZeroDivisionError:
        return "Cannot divide by zero"
    except TypeError:
        return "Invalid types provided"
    except Exception as e:
        return f"Unexpected error: {e}"
    else:
        return result
    finally:
        print("Division attempted")

print(safe_divide(10, 2))
print(safe_divide(10, 0))
print(safe_divide(10, "2"))

class ValidationError(Exception):
    pass

def validate_age(age):
    if age < 0:
        raise ValidationError("Age cannot be negative")
    if age > 150:
        raise ValidationError("Age seems unrealistic")
    return "Valid age"

try:
    print(validate_age(25))
    print(validate_age(-5))
except ValidationError as e:
    print("Error:", e)