在python中遍历字典中的字典

data = {
    'user1': {'name': 'Alice', 'age': 25, 'city': 'New York'},
    'user2': {'name': 'Bob', 'age': 30, 'city': 'Los Angeles'},
    'user3': {'name': 'Charlie', 'age': 35, 'city': 'Chicago'}
}

for key, value in data.items():
    print(f"User ID: {key}")
    for sub_key, sub_value in value.items():
        print(f"  {sub_key}: {sub_value}")

for key, value in data.items():
    if isinstance(value, dict):
        for sub_key, sub_value in value.items():
            print(f"  {sub_key}: {sub_value}")

for key in data:
    name = data.get(key, {}).get('name', 'Unknown')
    print(f"User ID: {key}, Name: {name}")