100 Days Of Python - Day 12

Day 12

Scope

• Scope refers to the visibility of variables.
• Variables defined outside of a function are accessible inside the function.
• Variables defined inside a function are not accessible outside the function.

enemies = 1

def increase_enemies():
    enemies = 2
    print(f"enemies inside function: {enemies}")

increase_enemies()
print(f"enemies outside function: {enemies}")

# Output:
# enemies inside function: 2
# enemies outside function: 1

Local Scope

• Variables defined in functions are only accessible in the function.
• Variables defined in functions are called local variables.

def drink_potion():
    potion_strength = 2
    print(potion_strength)

drink_potion()
print(potion_strength)

# Output:
# 2
# NameError: name 'potion_strength' is not defined

Global Scope

• Variables defined outside of functions are called global variables.
• Global variables are accessible inside functions.

player_health = 10

def drink_potion():
    potion_strength = 2
    print(player_health)

drink_potion()
print(player_health)

# Output:
# 10
# 10

Namespace

• A namespace is a collection of names.
• Each namespace has its own scope.
• There can be local, global, and built-in namespaces.
• The built-in namespace contains functions like print(), input(), len(), etc.
• The global namespace contains variables defined outside of functions.
• The local namespace contains variables defined inside functions.
• The local namespace is created when a function is called, and is destroyed when the function returns.
• The global namespace is created when the program starts, and is destroyed when the program ends.
• The built-in namespace is created when the program starts, and is destroyed when the program ends.
• The local namespace can access the global and built-in namespaces.
• The global namespace can access the built-in namespace.
• The built-in namespace cannot access the global or local namespaces.

There is no Block Scope

• In some programming languages, variables defined inside if statements are not accessible outside of the if statement.
• This is called block scope.
• Python does not have block scope.
• Variables defined inside if statements are accessible outside of the if statement.

game_level = 3
enemies = ["Skeleton", "Zombie", "Alien"]

if game_level < 5:
    new_enemy = enemies[0]

print(new_enemy)

# Output:
# Skeleton

Modifying Global Scope

• If you want to modify a global variable inside a function, use the global keyword.

enemies = 1

def increase_enemies():
    global enemies
    enemies = 2
    print(f"enemies inside function: {enemies}")

increase_enemies()
print(f"enemies outside function: {enemies}")

# Output:
# enemies inside function: 2
# enemies outside function: 2

• If you want to modify a global variable inside a function, use the global keyword.

enemies = 1

def increase_enemies():
    global enemies
    enemies = 2
    print(f"enemies inside function: {enemies}")

increase_enemies()
print(f"enemies outside function: {enemies}")

# Output:
# enemies inside function: 2
# enemies outside function: 2

Global Constants

• Global constants are variables that are accessible everywhere, but cannot be modified.
• Global constants are usually written in ALL_CAPS.

PI = 3.14159
URL = "https://www.google.com"
TWITTER_HANDLE = "@jack"

The Number Guessing Game

Instructions:

• You are going to build a higher or lower game.

The game works like this:

• The computer randomly chooses a number between 0 and 100.
• The user is then asked to guess a number.
• If the user’s guess is higher than the computer’s number, then the user is told to go lower.
• If the user’s guess is lower than the computer’s number, then the user is told to go higher.
• Then the user is asked to guess again.
• This process repeats until the user guesses the computer’s number.
• Once the user guesses the computer’s number, the game restarts.
• Important Print “It’s higher” or “It’s lower” to give the user a hint. If they guess the number correctly, tell them they got it right, and the game is over.
• Hint: you can generate a random number between 0 and 100 using:

  import random
  print(random.randint(0, 100))
  

import random

EASY_LEVEL_TURNS = 10
HARD_LEVEL_TURNS = 5

def set_difficulty():
    level = input("Choose a difficulty. Type 'easy' or 'hard': ")
    if level == "easy":
        return EASY_LEVEL_TURNS
    else:
        return HARD_LEVEL_TURNS

def check_answer(guess, answer, turns):
    """Checks answer against guess. Returns the number of turns remaining."""
    if guess > answer:
        print("Too high.")
        return turns - 1
    elif guess < answer:
        print("Too low.")
        return turns - 1
    else:
        print(f"You got it! The answer was {answer}.")

def game():
    print("Welcome to the Number Guessing Game!")
    print("I'm thinking of a number between 1 and 100.")
    answer = random.randint(1, 100)
    print(f"Pssst, the correct answer is {answer}")

    turns = set_difficulty()
    guess = 0
    while guess != answer:
        print(f"You have {turns} attempts remaining to guess the number.")

        guess = int(input("Make a guess: "))

        turns = check_answer(guess, answer, turns)
        if turns == 0:
            print("You've run out of guesses, you lose.")
            return
        elif guess != answer:
            print("Guess again.")

game()

# Output:
# Welcome to the Number Guessing Game!
# I'm thinking of a number between 1 and 100.
# Pssst, the correct answer is 87
# Choose a difficulty. Type 'easy' or 'hard': hard
# You have 5 attempts remaining to guess the number.
# Make a guess: 50
# Too low.
# Guess again.
# You have 4 attempts remaining to guess the number.
# Make a guess: 75
# Too high.

# ...