# Basic safe key access
person = {'name': 'Alice', 'age': 25}
city = person.get('city', 'Unknown')
print(f"City: {city}")  # City: Unknown

# Different ways to handle missing keys
person = {'name': 'Alice', 'age': 25}

# Using get() method
city = person.get('city', 'Unknown')
print(f"City: {city}")

# Using in operator
if 'email' in person:
    print(f"Email: {person['email']}")
else:
    print("Email not found")

# Using try/except
try:
    phone = person['phone']
    print(f"Phone: {phone}")
except KeyError:
    print("Phone not found")

# Using setdefault()
email = person.setdefault('email', 'no-email@example.com')
print(f"Email set to: {email}")
print(f"Updated person: {person}")

# Advanced missing key handling
from collections import defaultdict, ChainMap

# Using defaultdict
scores = defaultdict(int)
scores['Alice'] = 85
scores['Bob'] = 92
print(f"Charlie's score: {scores['Charlie']}")  # Returns 0

# Using defaultdict with list
groups = defaultdict(list)
groups['students'].append('Alice')
groups['teachers'].append('Bob')
print(f"Groups: {dict(groups)}")

# Using ChainMap for fallbacks
defaults = {'theme': 'dark', 'language': 'en'}
user_prefs = {'theme': 'light'}
config = ChainMap(user_prefs, defaults)
print(f"Theme: {config['theme']}")      # light
print(f"Language: {config['language']}")  # en

# Custom default function
def get_with_fallback(dictionary, key, fallback_func):
    if key in dictionary:
        return dictionary[key]
    return fallback_func()

def default_name():
    return "Anonymous User"

name = get_with_fallback(person, 'username', default_name)
print(f"Username: {name}")