Python Codenames = ["Alice", "Bob", "Charlie"] for name in names: print(f"Hello, {name}!")Back (Explanation): This code iterates through a list of names. For each name in the list, it prints a greeting. Key Takeaway: The for loop repeats an action for every item in a sequence. The f"..." is an f-string, which inserts the value of name directly into the text.

names = ["Alice", "Bob", "Charlie"]
for name in names:
    print(f"Hello, {name}!")

This code iterates through a list of names. For each name in the list, it prints a greeting.

• Key Takeaway: The for loop repeats an action for every item in a sequence. The f"..." is an f-string, which inserts the value of name directly into the text.

numbers = [1, 2, 3, 4, 5]
squares = [n**2 for n in numbers if n % 2 == 0]

This code creates a new list called squares. It takes each number (n) from the numbers list, checks if it is even (n % 2 == 0), and if so, squares it (n**2). The resulting list will be [4, 16].

• Key Takeaway: List comprehensions are a compact way to filter and transform lists in a single line

config = {"timeout": 30, "retry": True}
timeout_value = config.get("timeout", 60)
max_connections = config.get("connections", 10config = {"timeout": 30, "retry": True}
timeout_value = config.get("timeout", 60)
max_connections = config.get("connections", 10)

This code reads values from a dictionary called config. It uses the .get() method to retrieve values safely. timeout_value will be 30 (because it exists in the dictionary), while max_connections will be the default fallback 10 (because "connections" is not in the dictionary).

• Key Takeaway: Using .get(key, default) prevents the code from crashing if a key doesn't exist.

def calculate_discount(price: float, discount_rate: float = 0.1) -> float:
    return price - (price * discount_rate)

This defines a function named calculate_discount that takes a price and an optional discount_rate (which defaults to 10% or 0.1). It returns the final price after the discount. The : float and -> float are type hints indicating what kind of data goes in and comes out.

• Key Takeaway: Functions encapsulate reusable logic, and default parameters allow you to call the function with fewer arguments.

try:
    result = 10 / 0
except ZeroDivisionError:
    result = 0
    print("Cannot divide by zero. Defaulting to 0.")

This code attempts to divide 10 by 0, which normally crashes a program. The try block catches this specific error (ZeroDivisionError), allowing the except block to handle it gracefully by setting result to 0 and printing a warning.

• Key Takeaway: try-except blocks protect your program from unexpected crashes by catching and managing errors.

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

This code opens a file named data.txt in read mode ("r"). The with statement acts as a context manager, meaning it automatically handles opening the file and, crucially, making sure it is properly closed when the block of code finishes—even if an error occurs while reading.

• Key Takeaway: Always use the with statement when dealing with external resources like files or network connections to ensure they are safely cleaned up.

tasks = ["Deploy server", "Update database", "Restart services"]
for index, task in enumerate(tasks, start=1):
    print(f"Task {index}: {task}")

This code loops over the tasks list, but instead of just giving you the item, enumerate() gives you both the index (count) and the item itself. By passing start=1, the numbering begins at 1 instead of the default 0.

• Key Takeaway: Use enumerate() when you need both the value of an item and its position (index) within a loop.

class NetworkNode:
    def __init__(self, ip_address):
        self.ip_address = ip_address
        self.status = "Offline"

    def connect(self):
        self.status = "Online"

node_1 = NetworkNode("10.0.0.5")
node_1.connect()

This defines a blueprint (a class) for creating NetworkNode objects. The __init__ method sets the initial state (an IP address and an "Offline" status) when a new node is created. We create node_1, then call its .connect() method to change its status to "Online".

• Key Takeaway: Classes bundle data (ip_address, status) and the actions that modify that data (connect()) together into a single object.

logs = ["Error: 404", "Warning: High CPU", "Info: Restart", "Error: 500"]
recent_logs = logs[-2:]
reversed_logs = logs[::-1]

This code uses slicing to extract specific parts of a list. Slicing uses the format [start:stop:step]. logs[-2:] grabs the last two items in the list. logs[::-1] uses a step of -1 to step backward through the entire list, effectively reversing it.

• Key Takeaway: List slicing is a fast and powerful way to extract subsets of data or reverse sequences without writing loops.