Membership Operators

# Checking substrings and characters in strings
message = "Hello, welcome to Python programming!"

# Using 'in' operator
contains_python = "Python" in message
print(contains_python)  # Output: True

contains_java = "Java" in message
print(contains_java)  # Output: False

# Case sensitivity matters
contains_python_lowercase = "python" in message
print(contains_python_lowercase)  # Output: False

# Checking for characters
has_spaces = " " in message
print(has_spaces)  # Output: True

# Using 'not in' operator
no_java = "Java" not in message
print(no_java)  # Output: True

no_python = "Python" not in message
print(no_python)  # Output: False

# Practical example with validation
email = "user@example.com"
if "@" not in email:
    print("Invalid email: missing @ symbol")
else:
    print("Email format looks valid")  # This will print

# Working with lists
fruits = ["apple", "banana", "orange", "mango"]
vegetables = ["carrot", "broccoli", "spinach", "potato"]

# Using 'in' operator
has_apple = "apple" in fruits
print(has_apple)  # Output: True

has_pear = "pear" in fruits
print(has_pear)  # Output: False

# Using 'not in' operator
no_tomato = "tomato" not in vegetables
print(no_tomato)  # Output: True

no_carrot = "carrot" not in vegetables
print(no_carrot)  # Output: False

# Practical example with conditional statements
shopping_list = ["milk", "bread", "eggs", "cheese"]
item_to_buy = "milk"

if item_to_buy in shopping_list:
    print(f"{item_to_buy} is already on the shopping list")  # This will print
else:
    shopping_list.append(item_to_buy)
    print(f"Added {item_to_buy} to the shopping list")

# Check for items NOT on the list
essential_items = ["milk", "bread", "butter"]
missing_items = []

for item in essential_items:
    if item not in shopping_list:
        missing_items.append(item)

print("Missing items:", missing_items)  # Output: Missing items: ['butter']

# Working with tuples
coordinates = (10, 20, 30, 40, 50)
days_of_week = ("Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday")

# Using 'in' operator
has_30 = 30 in coordinates
print(has_30)  # Output: True

has_35 = 35 in coordinates
print(has_35)  # Output: False

is_weekday = "Monday" in days_of_week
print(is_weekday)  # Output: True

# Using 'not in' operator
not_35 = 35 not in coordinates
print(not_35)  # Output: True

not_monday = "Monday" not in days_of_week
print(not_monday)  # Output: False

# Practical example with validation
valid_grades = ("A", "B", "C", "D", "F")
student_grade = "B+"

if student_grade in valid_grades:
    print("Grade is valid")
else:
    print("Invalid grade entered")  # This will print

if student_grade not in valid_grades:
    print(f"'{student_grade}' is not a standard grade")  # This will print

# Working with dictionaries
student = {
    "name": "Alex",
    "age": 21,
    "major": "Computer Science",
    "gpa": 3.8
}

# Using 'in' operator (checks keys by default)
has_name_key = "name" in student
print(has_name_key)  # Output: True

has_grade_key = "grade" in student
print(has_grade_key)  # Output: False

# Using 'not in' operator (checks keys by default)
no_grade_key = "grade" not in student
print(no_grade_key)  # Output: True

no_name_key = "name" not in student
print(no_name_key)  # Output: False

# Checking values (not keys)
has_alex_value = "Alex" in student.values()
print(has_alex_value)  # Output: True

no_bob_value = "Bob" not in student.values()
print(no_bob_value)  # Output: True

# Practical example with user data
user_profile = {"username": "john_doe", "email": "john@email.com"}
required_fields = ["username", "email", "password"]

missing_fields = []
for field in required_fields:
    if field not in user_profile:
        missing_fields.append(field)

if missing_fields:
    print("Missing required fields:", missing_fields)  # Output: Missing required fields: ['password']
else:
    print("All required fields are present")

# Working with sets
allowed_colors = {"red", "green", "blue", "yellow"}
forbidden_ingredients = {"peanuts", "shellfish", "dairy"}

# Using 'in' operator
is_red_allowed = "red" in allowed_colors
print(is_red_allowed)  # Output: True

is_purple_allowed = "purple" in allowed_colors
print(is_purple_allowed)  # Output: False

has_peanuts = "peanuts" in forbidden_ingredients
print(has_peanuts)  # Output: True

# Using 'not in' operator
no_purple = "purple" not in allowed_colors
print(no_purple)  # Output: True

no_red = "red" not in allowed_colors
print(no_red)  # Output: False

safe_ingredient = "flour" not in forbidden_ingredients
print(safe_ingredient)  # Output: True

# Practical example with permissions
user_permissions = {"read", "write", "delete"}
admin_permissions = {"read", "write", "delete", "admin", "manage_users"}

action = "delete"
if action in user_permissions:
    print(f"User can perform: {action}")  # This will print
else:
    print(f"Access denied for: {action}")

special_action = "manage_users"
if special_action not in user_permissions:
    print(f"User cannot perform: {special_action}")  # This will print

# Check if any of several values exist in a collection
dietary_preferences = ["vegetarian", "gluten-free", "dairy-free"]
restricted_diets = ["keto", "paleo", "low-carb"]

# Using 'in' with multiple checks
is_vegan = "vegan" in dietary_preferences                   # False
is_vegetarian = "vegetarian" in dietary_preferences    # True
is_plant_based = is_vegan or is_vegetarian                   # False or True → True
print("Has plant-based preference:", is_plant_based)  # Output: Has plant-based preference: True

# Using 'not in' with multiple checks
has_no_restrictions = all(diet not in dietary_preferences for diet in restricted_diets)
print("Has no restricted diets:", has_no_restrictions)  # Output: Has no restricted diets: True

# Method using any() function
has_any_restriction = any(diet in dietary_preferences for diet in restricted_diets)
print("Has restricted diet:", has_any_restriction)  # Output: Has restricted diet: False