Dictionary Methods

person = {"name": "Alice", "age": 25, "city": "Mumbai"}

# Iterating
for key in person:
    print(f"{key}: {person[key]}")

# .keys(), .values(), .items()
print(list(person.keys()))    # ['name', 'age', 'city']
print(list(person.values()))  # ['Alice', 25, 'Mumbai']
print(list(person.items()))   # [('name','Alice'), ...]

# Best way to iterate
for key, value in person.items():
    print(f"{key}: {value}")

# .update() — merge dictionaries
defaults = {"theme": "dark", "lang": "en"}
user_prefs = {"theme": "light"}
defaults.update(user_prefs)
print(defaults)  # {'theme': 'light', 'lang': 'en'}

# Python 3.9+ merge operator
merged = defaults | user_prefs
print(merged)

# .setdefault() — set only if missing
config = {"host": "localhost"}
config.setdefault("port", 8080)   # adds port
config.setdefault("host", "0.0.0.0")  # doesn't change
print(config)  # {'host': 'localhost', 'port': 8080}

# Counting pattern
text = "hello world"
counts = {}
for char in text:
    counts[char] = counts.get(char, 0) + 1
print(counts)