🐍 Python Basics

print("Hello, World!")
print("Welcome to Python!")

# This is a comment
# Output: Hello, World!
#         Welcome to Python!

# Numbers
age = 25              # int
price = 19.99         # float
complex_num = 3 + 4j  # complex

# Strings
name = "Alice"
message = 'Hello World'
multiline = """This is
a multiline string"""

# Boolean
is_active = True
has_discount = False

# None (null value)
result = None

# Check type
print(type(age))      # 
print(type(price))    # 
print(type(name))     # 

# Convert between types
x = "100"
y = int(x)        # String to int
z = float(x)      # String to float
w = str(50)       # Number to string

print(y + 50)     # 150
print(z + 0.5)    # 100.5
print(w + "0")    # "500"

a = 10
b = 3

print(a + b)   # 13  Addition
print(a - b)   # 7   Subtraction
print(a * b)   # 30  Multiplication
print(a / b)   # 3.333... Division (float)
print(a // b)  # 3   Floor division (int)
print(a % b)   # 1   Modulus (remainder)
print(a ** b)  # 1000 Exponentiation

x = 5
y = 10

print(x == y)  # False  Equal to
print(x != y)  # True   Not equal to
print(x < y)   # True   Less than
print(x > y)   # False  Greater than
print(x <= y)  # True   Less than or equal
print(x >= y)  # False  Greater than or equal

a = True
b = False

print(a and b)  # False  Both must be True
print(a or b)   # True   At least one True
print(not a)    # False  Negation

# String operations
text = "Hello, Python!"

# Indexing and slicing
print(text[0])       # 'H'
print(text[-1])      # '!'
print(text[0:5])     # 'Hello'
print(text[7:])      # 'Python!'

# String methods
print(text.upper())           # 'HELLO, PYTHON!'
print(text.lower())           # 'hello, python!'
print(text.replace("Python", "World"))  # 'Hello, World!'
print(text.split(","))        # ['Hello', ' Python!']
print(len(text))              # 14

# String formatting
name = "Alice"
age = 25
print(f"My name is {name} and I'm {age} years old")
print("My name is {} and I'm {} years old".format(name, age))

# Create lists
fruits = ["apple", "banana", "cherry"]
numbers = [1, 2, 3, 4, 5]
mixed = [1, "hello", 3.14, True]

# Accessing elements
print(fruits[0])      # 'apple'
print(fruits[-1])     # 'cherry'

# Slicing
print(numbers[1:4])   # [2, 3, 4]
print(numbers[:3])    # [1, 2, 3]
print(numbers[2:])    # [3, 4, 5]

# List methods
fruits.append("orange")      # Add to end
fruits.insert(1, "mango")    # Insert at index
fruits.remove("banana")      # Remove by value
fruits.pop()                 # Remove last item
fruits.sort()                # Sort in place
print(len(fruits))           # Length

# List operations
list1 = [1, 2, 3]
list2 = [4, 5, 6]
combined = list1 + list2     # [1, 2, 3, 4, 5, 6]
repeated = list1 * 2         # [1, 2, 3, 1, 2, 3]

# Check membership
print("apple" in fruits)     # True
print("grape" not in fruits) # True

# Create tuples
coordinates = (10, 20)
colors = ("red", "green", "blue")
single_item = (42,)  # Note the comma for single item

# Accessing elements
print(coordinates[0])  # 10
print(colors[-1])      # 'blue'

# Tuple unpacking
x, y = coordinates
print(x)  # 10
print(y)  # 20

# Tuple methods
numbers = (1, 2, 3, 2, 4, 2)
print(numbers.count(2))  # 3
print(numbers.index(3))  # 2

# Why use tuples?
# - Faster than lists
# - Protect data from modification
# - Can be used as dictionary keys

# Create dictionaries
person = {
    "name": "Alice",
    "age": 25,
    "city": "New York"
}

# Accessing values
print(person["name"])        # 'Alice'
print(person.get("age"))     # 25
print(person.get("email", "Not found"))  # 'Not found'

# Modifying dictionaries
person["age"] = 26           # Update value
person["email"] = "alice@example.com"  # Add new key
del person["city"]           # Remove key
person.pop("email")          # Remove and return value

# Dictionary methods
print(person.keys())         # dict_keys(['name', 'age'])
print(person.values())       # dict_values(['Alice', 26])
print(person.items())        # dict_items([('name', 'Alice'), ('age', 26)])

# Check membership
print("name" in person)      # True

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

# Create sets
fruits = {"apple", "banana", "cherry"}
numbers = set([1, 2, 3, 2, 1])  # {1, 2, 3} - duplicates removed

# Set operations
fruits.add("orange")         # Add element
fruits.remove("banana")      # Remove (raises error if not found)
fruits.discard("grape")      # Remove (no error if not found)

# Set mathematics
set1 = {1, 2, 3, 4}
set2 = {3, 4, 5, 6}

print(set1 | set2)           # {1, 2, 3, 4, 5, 6} Union
print(set1 & set2)           # {3, 4} Intersection
print(set1 - set2)           # {1, 2} Difference
print(set1 ^ set2)           # {1, 2, 5, 6} Symmetric difference

# Check membership
print(1 in set1)             # True

age = 18

if age < 13:
    print("Child")
elif age < 20:
    print("Teenager")
else:
    print("Adult")

# Ternary operator
status = "Adult" if age >= 18 else "Minor"

# Loop through list
fruits = ["apple", "banana", "cherry"]
for fruit in fruits:
    print(fruit)

# Loop with index
for i, fruit in enumerate(fruits):
    print(f"{i}: {fruit}")

# Loop through range
for i in range(5):        # 0 to 4
    print(i)

for i in range(2, 10, 2): # 2 to 9, step 2
    print(i)              # 2, 4, 6, 8

# Loop through dictionary
person = {"name": "Alice", "age": 25}
for key, value in person.items():
    print(f"{key}: {value}")

count = 0
while count < 5:
    print(count)
    count += 1

# Break and continue
for i in range(10):
    if i == 3:
        continue  # Skip 3
    if i == 7:
        break     # Stop at 7
    print(i)

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

print(greet("Alice"))  # Hello, Alice!

# Default parameters
def greet(name, greeting="Hello"):
    return f"{greeting}, {name}!"

print(greet("Bob"))              # Hello, Bob!
print(greet("Bob", "Hi"))        # Hi, Bob!

# Multiple return values
def get_coordinates():
    return 10, 20

x, y = get_coordinates()

# *args and **kwargs
def sum_all(*args):
    return sum(args)

print(sum_all(1, 2, 3, 4))  # 10

def print_info(**kwargs):
    for key, value in kwargs.items():
        print(f"{key}: {value}")

print_info(name="Alice", age=25)

# Docstrings
def add(a, b):
    """
    Add two numbers and return the result.
    
    Args:
        a: First number
        b: Second number
    
    Returns:
        Sum of a and b
    """
    return a + b

# Basic lambda
square = lambda x: x ** 2
print(square(5))  # 25

add = lambda x, y: x + y
print(add(3, 4))  # 7

# Lambda with map
numbers = [1, 2, 3, 4, 5]
squared = list(map(lambda x: x ** 2, numbers))
print(squared)  # [1, 4, 9, 16, 25]

# Lambda with filter
even_numbers = list(filter(lambda x: x % 2 == 0, numbers))
print(even_numbers)  # [2, 4]

# Lambda with sorted
students = [
    {"name": "Alice", "grade": 85},
    {"name": "Bob", "grade": 92},
    {"name": "Charlie", "grade": 78}
]
sorted_students = sorted(students, key=lambda x: x["grade"], reverse=True)
print(sorted_students)

# List comprehension
squares = [x ** 2 for x in range(10)]
print(squares)  # [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

# With condition
even_squares = [x ** 2 for x in range(10) if x % 2 == 0]
print(even_squares)  # [0, 4, 16, 36, 64]

# Nested comprehension
matrix = [[i * j for j in range(3)] for i in range(3)]
print(matrix)  # [[0, 0, 0], [0, 1, 2], [0, 2, 4]]

# Dictionary comprehension
squares_dict = {x: x ** 2 for x in range(5)}
print(squares_dict)  # {0: 0, 1: 1, 2: 4, 3: 9, 4: 16}

# Set comprehension
unique_lengths = {len(word) for word in ["hello", "world", "hi", "python"]}
print(unique_lengths)  # {2, 5, 6}

class Dog:
    # Class attribute
    species = "Canis familiaris"
    
    # Constructor
    def __init__(self, name, age):
        # Instance attributes
        self.name = name
        self.age = age
    
    # Instance method
    def bark(self):
        return f"{self.name} says Woof!"
    
    # String representation
    def __str__(self):
        return f"{self.name} is {self.age} years old"

# Create objects
dog1 = Dog("Buddy", 3)
dog2 = Dog("Max", 5)

print(dog1.bark())  # Buddy says Woof!
print(dog1)         # Buddy is 3 years old

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

class Dog(Animal):
    def speak(self):
        return f"{self.name} says Woof!"

class Cat(Animal):
    def speak(self):
        return f"{self.name} says Meow!"

# Polymorphism
animals = [Dog("Buddy"), Cat("Whiskers")]
for animal in animals:
    print(animal.speak())

class BankAccount:
    def __init__(self, balance):
        self.__balance = balance  # Private attribute
    
    def deposit(self, amount):
        if amount > 0:
            self.__balance += amount
    
    def withdraw(self, amount):
        if 0 < amount <= self.__balance:
            self.__balance -= amount
            return True
        return False
    
    def get_balance(self):
        return self.__balance

account = BankAccount(1000)
account.deposit(500)
print(account.get_balance())  # 1500

# Import entire module
import math
print(math.sqrt(16))  # 4.0
print(math.pi)        # 3.141592653589793

# Import specific items
from math import sqrt, pi
print(sqrt(25))  # 5.0

# Import with alias
import numpy as np
import pandas as pd

# Import all (not recommended)
from math import *

# Standard library modules
import datetime
import random
import os

# Get current date
today = datetime.date.today()
print(today)

# Random number
print(random.randint(1, 10))

# File path operations
print(os.path.exists("file.txt"))

# Read entire file
with open("file.txt", "r") as file:
    content = file.read()
    print(content)

# Read line by line
with open("file.txt", "r") as file:
    for line in file:
        print(line.strip())

# Read all lines into list
with open("file.txt", "r") as file:
    lines = file.readlines()
    print(lines)

# Write to file (overwrites existing)
with open("output.txt", "w") as file:
    file.write("Hello, World!\n")
    file.write("Python is awesome!")

# Append to file
with open("output.txt", "a") as file:
    file.write("\nAppended line")

# Write multiple lines
lines = ["Line 1\n", "Line 2\n", "Line 3\n"]
with open("output.txt", "w") as file:
    file.writelines(lines)

import csv

# Read CSV
with open("data.csv", "r") as file:
    reader = csv.reader(file)
    for row in reader:
        print(row)

# Write CSV
data = [
    ["Name", "Age", "City"],
    ["Alice", "25", "New York"],
    ["Bob", "30", "London"]
]

with open("output.csv", "w", newline="") as file:
    writer = csv.writer(file)
    writer.writerows(data)

# CSV with dictionaries
with open("data.csv", "r") as file:
    reader = csv.DictReader(file)
    for row in reader:
        print(row["Name"], row["Age"])

import json

# Python dict to JSON
data = {
    "name": "Alice",
    "age": 25,
    "skills": ["Python", "JavaScript"]
}

# Write JSON file
with open("data.json", "w") as file:
    json.dump(data, file, indent=4)

# Read JSON file
with open("data.json", "r") as file:
    loaded_data = json.load(file)
    print(loaded_data)

# JSON string conversions
json_string = json.dumps(data)
python_dict = json.loads(json_string)