Python Playground

# Hello World
print("Hello from code sample!")

# Variables, Types, and Simple Math
x = 10
y = 3.14
text = "Python"
  
print(x, y, text)
print(type(x), type(y), type(text))
  
# Simple Math
sum_xy = x + y
print("x + y =", sum_xy)

# Explicit & Implicit Conversions
a = "42"     # string
b = 8        # integer

# Explicit
num_a = int(a)   # convert string to int
print("Result of num_a + b:", num_a + b)

# Implicit might happen in some contexts, but Python is fairly strict
# For instance, str + int won't automatically convert, so we must do it ourselves:
print("Combined string:", a + str(b))

# String Manipulation
message = "Hello, World!"
print("Original:", message)
print("Lowercase:", message.lower())
print("Uppercase:", message.upper())
print("Substring:", message[0:5])       # 'Hello'
print("Split:", message.split(","))     # ['Hello', ' World!']
print("Replace:", message.replace("World", "Python"))

# Strings Advanced
message = "Concatenation " + "example!"
formatted = f"This is {message} with an integer {42}"

multi_line = """This 
is 
multiple lines"""

print("Joined string:", formatted)
print("Multiline string:\n", multi_line)

# Center & count
print("Centered:", message.center(30, '*'))
print("Count of 'a':", message.count('a'))

# If-Else and Elif
age = 18
if age < 18:
    print("Minor")
elif age == 18:
    print("Just turned adult")
else:
    print("Adult")

# For, While, and Range
print("For loop from 0 to 4:")
for i in range(5):
    print(i)

print("While loop example:")
j = 0
while j < 3:
    print("j =", j)
    j += 1

# Loops Advanced
items = [("apple", 3), ("banana", 2), ("cherry", 5)]

# Using enumerate
for index, (fruit, qty) in enumerate(items):
    print(f"Item #{index} is {fruit} with qty {qty}")

# Using zip
names = ["Alice", "Bob", "Charlie"]
scores = [90, 85, 92]
for n, s in zip(names, scores):
    print(n, "scored", s)

# Break & Continue
for i in range(1, 6):
    if i == 3:
        continue
    if i == 5:
        break
    print(i)

# Lists: creation, indexing, slicing
fruits = ["apple", "banana", "cherry"]
fruits.append("date")
print("Fruits:", fruits)
print("First fruit:", fruits[0])
print("Slice (1:3):", fruits[1:3]) # banana, cherry

# List comprehension
numbers = [x for x in range(5)]
print("List comprehension:", numbers)

# Lists Advanced
nums = [1, 2, 3, 4, 5]
nums[2:4] = [9, 9]  # in-place replacement
print("Modified list:", nums)

# Sorting with a key
words = ["apple", "bat", "atom", "banana"]
words.sort(key=len)
print("Sorted by length:", words)

# map & filter
squared = list(map(lambda x: x*x, nums))
filtered = list(filter(lambda x: x > 2, nums))
print("Squared:", squared)
print("Filtered > 2:", filtered)

# Tuples & Sets
my_tuple = (1, 2, 3)
print("Tuple:", my_tuple)
# my_tuple[0] = 99 # This would error, tuples are immutable

my_set = {1, 2, 2, 3, 4}
my_set.add(5)
print("Set (unique values):", my_set)
print("Does the set contain 2?", 2 in my_set)

# Tuple & Set Advanced
nested_tuple = ((1, 2), (3, 4))
print("Nested tuple:", nested_tuple)

# Set operations
setA = {1, 2, 3}
setB = {3, 4, 5}
print("Union:", setA | setB)
print("Intersection:", setA & setB)
print("Difference:", setA - setB)

# Dictionaries
person = {"name": "Alice", "age": 30}
person["city"] = "New York"
print("Person dictionary:", person)
print("Name:", person["name"])
print("Keys:", person.keys())
print("Values:", person.values())

# Dictionaries Advanced
person = {"name": "Alice", "age": 30, "city": "NY"}
print("Country:", person.get("country", "Unknown"))

# dictionary comprehension
squares = {x: x*x for x in range(1,6)}
print("Squares dict:", squares)

# Merging dictionaries (Python 3.9+)
extra = {"job": "Engineer"}
merged = {**person, **extra}
print("Merged dict:", merged)

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

message = greet("Alice")
print(message)

# Function with default parameter
def power(base, exponent=2):
    return base ** exponent

print("power(5) =", power(5))       # uses exponent=2
print("power(5,3) =", power(5, 3))  # custom exponent

# Functions Advanced
# *args and **kwargs
def demo_args(*args, **kwargs):
    print("args:", args)
    print("kwargs:", kwargs)

demo_args(1, 2, 3, name="Bob", job="Developer")

# Nested function
def outer(x):
    def inner(y):
        return x + y
    return inner

add_to_5 = outer(5)
print("Result from nested function:", add_to_5(10))

# Importing Modules
import math

print("math.sqrt(16) =", math.sqrt(16))
print("math.pi =", math.pi)

# You can also do: from math import pi, sqrt

# Modules Advanced
import math
import random

# Checking Python version
print("Python version:", __import__('sys').version)

# random usage
for i in range(3):
    print("Random float 0-1:", random.random())

# math.comb in Python 3.8+ (binomial coefficient)
print("Combinations of 5 choose 2:", math.comb(5,2))

# Classes and Objects (OOP)
class Animal:
    def __init__(self, name):
        self.name = name

    def speak(self):
        print(self.name, "makes a noise.")

class Dog(Animal):
    def speak(self):
        print(self.name, "barks!")

dog = Dog("Rex")
dog.speak()

# OOP Advanced
class Shape:
    def area(self):
        raise NotImplementedError("Please implement 'area' method")

class Rectangle(Shape):
    def __init__(self, w, h):
        self.w = w
        self.h = h

    @property
    def area(self):
        return self.w * self.h

rect = Rectangle(3, 4)
print("Rectangle area:", rect.area)

# Class & static methods
class MyClass:
    class_var = 10

    @classmethod
    def class_method(cls):
        print("class_var =", cls.class_var)

    @staticmethod
    def static_method():
        print("Static method called")

MyClass.class_method()
MyClass.static_method()

# Exceptions and Try-Except
try:
    num = int("abc")  # invalid integer
except ValueError as e:
    print("Caught ValueError:", e)
finally:
    print("This finally block always executes.")

# More on List Comprehensions
numbers = [1, 2, 3, 4, 5]
squares = [n*n for n in numbers]
evens = [n for n in numbers if n % 2 == 0]

print("Numbers:", numbers)
print("Squares:", squares)
print("Evens:", evens)

# NumPy Basics
import numpy as np

arr = np.array([1, 2, 3, 4])
print("NumPy Array:", arr)

# Some operations
print("Shape:", arr.shape)
print("Mean:", arr.mean())
print("Sum:", arr.sum())

# NumPy Advanced
import numpy as np

# Create a 3x3 random matrix
matrix = np.random.randn(3, 3)
print("Random 3x3 matrix:\n", matrix)

# Matrix multiplication
mat2 = np.array([[1,2,1],
                 [0,1,0],
                 [2,1,2]])
result = matrix.dot(mat2)
print("\nMatrix multiplication result:\n", result)

# Fancy indexing / slicing
first_col = matrix[:, 0]
print("\nFirst column:", first_col)

# Conditional selection
above_zero = matrix[matrix > 0]
print("\nElements above 0:", above_zero)

# Pandas Basics
import pandas as pd

data = {
    "Name": ["Alice", "Bob", "Charlie"],
    "Age": [25, 32, 18],
    "City": ["New York", "Paris", "London"]
}
df = pd.DataFrame(data)

print("DataFrame:")
print(df)
print()
print("Describe:")
print(df.describe())

# Pandas Advanced
import pandas as pd

# Sample data
sales = {
    "Store": ["A", "A", "B", "B", "C"],
    "Month": ["Jan", "Feb", "Jan", "Feb", "Jan"],
    "Revenue": [100, 150, 80, 120, 200]
}
df = pd.DataFrame(sales)

print("Original sales DataFrame:")
print(df)
print()

# Grouping by Store
grouped = df.groupby("Store")["Revenue"].sum()
print("Total revenue per Store:")
print(grouped)
print()

# Pivot Table
pivot = df.pivot_table(values="Revenue", index="Store", columns="Month", aggfunc="sum", fill_value=0)
print("Pivot Table:")
print(pivot)
print()

# Sorting
sorted_df = df.sort_values(by="Revenue", ascending=False)
print("Sorted by Revenue (descending):")
print(sorted_df)