Basics

python --version  # Should show something like Python 3.11.4

# This is a comment - Python ignores everything after #

# Variables - containers for storing data
name = "Python Learner"  # A string (text)
age = 25                 # An integer (whole number)
height = 5.9             # A float (decimal number)
is_coding = True         # A boolean (True/False)

# Printing to the console
print("Hello, " + name + "!")  # Output: Hello, Python Learner!
print(f"You are {age} years old")  # f-strings are awesome for formatting!

# Basic math operations
sum_value = 5 + 3    # Addition (8)
diff = 10 - 4        # Subtraction (6)
product = 4 * 5      # Multiplication (20)
quotient = 20 / 4    # Division (5.0) - always returns a float
power = 2 ** 3       # Exponentiation (8)
remainder = 10 % 3   # Modulus/remainder (1)

# Input from user
favorite_language = input("What's your favorite programming language? ")
print(f"Really? {favorite_language} is my favorite too!")

# If-Else statements
mood = "happy"

if mood == "happy":
    print("That's great!")
elif mood == "tired":
    print("Get some rest!")
else:
    print("Whatever you feel, it's valid.")

# While loops - repeat until a condition is met
count = 0
while count < 5:
    print(f"Count is {count}")
    count += 1  # Same as count = count + 1
    # Output: Count is 0, 1, 2, 3, 4

# For loops - iterate over a sequence
fruits = ["apple", "banana", "cherry"]
for fruit in fruits:
    print(f"I like {fruit}s")
    # Output: I like apples, I like bananas, I like cherrys

# Range - generate a sequence of numbers
for i in range(3):  # 0, 1, 2
    print(i)

# Lists - ordered, changeable collections
shopping_list = ["milk", "eggs", "bread"]
shopping_list.append("cheese")  # Add to the end
first_item = shopping_list[0]   # Access by index (starts at 0)
shopping_list[1] = "yogurt"     # Modify an item
shopping_list.remove("bread")   # Remove an item

# Slicing lists
numbers = [0, 1, 2, 3, 4, 5]
subset = numbers[1:4]  # Get items from index 1 to 3 (not including 4)
                       # Result: [1, 2, 3]

# Tuples - ordered, unchangeable collections
coordinates = (10.5, 20.8)  # Can't modify after creation
x, y = coordinates          # Unpacking values

# Dictionaries - key-value pairs
person = {
    "name": "Alex",
    "age": 30,
    "skills": ["Python", "SQL", "Problem-solving"]
}
print(person["name"])  # Access by key
person["location"] = "New York"  # Add new key-value pair

# Sets - unordered collections of unique items
unique_numbers = {1, 2, 3, 3, 2, 1}  # Result: {1, 2, 3}

# Basic function
def greet(name):
    """This function greets the person passed in as a parameter."""
    return f"Hello, {name}!"

# Call the function
message = greet("Friend")
print(message)  # Output: Hello, Friend!

# Function with default parameter
def power(base, exponent=2):
    """Raises base to the power of exponent."""
    return base ** exponent

print(power(3))     # Output: 9 (3^2)
print(power(2, 3))  # Output: 8 (2^3)

# *args and **kwargs for variable number of arguments
def make_pizza(size, *toppings, **preferences):
    """Makes a pizza with the given specifications."""
    print(f"Making a {size}-inch pizza with toppings:")
    for topping in toppings:
        print(f"- {topping}")
    if preferences:
        print("Special preferences:")
        for key, value in preferences.items():
            print(f"- {key}: {value}")

make_pizza("12", "cheese", "mushrooms", "pepperoni",
           crust="thin", extra_cheese=True)

# Importing built-in modules
import math
print(math.sqrt(16))  # Output: 4.0

# Importing specific functions
from random import randint
random_number = randint(1, 10)  # Random integer between 1 and 10

# Importing with an alias
import datetime as dt
current_date = dt.datetime.now()

# Creating your own module (in file_operations.py)
# def read_file(filename):
#     with open(filename, 'r') as f:
#         return f.read()
#
# def write_file(filename, content):
#     with open(filename, 'w') as f:
#         f.write(content)

# Then in your main file:
# import file_operations
# content = file_operations.read_file('data.txt')

# Writing to a file
with open('example.txt', 'w') as file:
    file.write("Hello, Python world!\n")
    file.write("This is a second line of text.")

# Reading from a file
with open('example.txt', 'r') as file:
    content = file.read()
    print(content)  # Prints all content at once

# Reading line by line
with open('example.txt', 'r') as file:
    for line in file:
        print(line.strip())  # strip() removes whitespace like newlines

# Working with CSV files
import csv

# Writing CSV
with open('data.csv', 'w', newline='') as file:
    writer = csv.writer(file)
    writer.writerow(["Name", "Age", "City"])
    writer.writerow(["Alice", 25, "New York"])
    writer.writerow(["Bob", 30, "San Francisco"])

# Reading CSV
with open('data.csv', 'r') as file:
    reader = csv.reader(file)
    for row in reader:
        print(row)  # Each row is a list

# Basic try-except
try:
    number = int(input("Enter a number: "))
    result = 10 / number
    print(f"10 divided by {number} is {result}")
except ValueError:
    print("That's not a valid number!")
except ZeroDivisionError:
    print("You can't divide by zero!")
except:
    print("Something else went wrong")
finally:
    print("This runs no matter what")

# Raising exceptions
def verify_age(age):
    if age < 0:
        raise ValueError("Age cannot be negative")
    if age > 150:
        raise ValueError("Are you sure about that age?")
    return f"Age verified: {age}"

try:
    print(verify_age(200))
except ValueError as error:
    print(f"Error: {error}")

# Defining a class
class Dog:
    # Class attribute
    species = "Canis familiaris"

    # Initializer / Constructor
    def __init__(self, name, age):
        self.name = name  # Instance attribute
        self.age = age    # Instance attribute

    # Instance method
    def bark(self):
        return f"{self.name} says Woof!"

    # Another instance method
    def birthday(self):
        self.age += 1
        return f"{self.name} is now {self.age} years old!"

# Creating instances of a class
buddy = Dog("Buddy", 5)
miles = Dog("Miles", 3)

print(buddy.name)  # Output: Buddy
print(miles.bark())  # Output: Miles says Woof!
print(buddy.birthday())  # Output: Buddy is now 6 years old!

# Inheritance - creating a subclass
class Bulldog(Dog):
    def bark(self):  # Override the bark method
        return f"{self.name} says WOOF WOOF!"

    def snore(self):  # Add a new method
        return f"{self.name} is snoring... Zzz..."

rocky = Bulldog("Rocky", 4)
print(rocky.bark())  # Output: Rocky says WOOF WOOF!
print(rocky.snore())  # Output: Rocky is snoring... Zzz...

# Install with: pip install numpy
import numpy as np

# Create arrays
arr = np.array([1, 2, 3, 4, 5])
print(arr * 2)  # Output: [2 4 6 8 10]

# Multi-dimensional arrays
matrix = np.array([[1, 2, 3], [4, 5, 6], [7, 8, 9]])
print(matrix.shape)  # Output: (3, 3)

# Math operations
print(np.mean(arr))  # Output: 3.0
print(np.std(arr))   # Standard deviation

# Install with: pip install pandas
import pandas as pd

# Create a DataFrame
data = {
    'Name': ['Alice', 'Bob', 'Charlie'],
    'Age': [25, 30, 35],
    'City': ['New York', 'San Francisco', 'Boston']
}
df = pd.DataFrame(data)
print(df)

# Reading from CSV
# df = pd.read_csv('data.csv')

# Basic operations
print(df['Age'].mean())  # Average age
print(df[df['Age'] > 25])  # Filter rows

# Groupby
result = df.groupby('City').mean()
print(result)

# Install with: pip install matplotlib
import matplotlib.pyplot as plt

# Simple line plot
x = [0, 1, 2, 3, 4]
y = [0, 1, 4, 9, 16]

plt.plot(x, y)
plt.title('Square Numbers')
plt.xlabel('x')
plt.ylabel('x²')
plt.show()  # This displays the plot