在循环中遍历嵌套字典

nested_dict = {
    'key1': {'subkey1': 'value1', 'subkey2': 'value2'},
    'key2': {'subkey3': 'value3'}
}

nested_dict = {
    'key1': {'subkey1': 'value1', 'subkey2': 'value2'},
    'key2': {'subkey3': 'value3'}
}

def traverse_nested_dict(d, prefix=''):
    for key, value in d.items():
        new_prefix = f"{prefix}.{key}" if prefix else key
        if isinstance(value, dict):
            traverse_nested_dict(value, new_prefix)
        else:
            print(f"{new_prefix}: {value}")

traverse_nested_dict(nested_dict)

key1.subkey1: value1
key1.subkey2: value2
key2.subkey3: value3

value = nested_dict.get('key1', {}).get('subkey1', 'default_value')

visited = set()

def traverse_nested_dict(d, prefix=''):
    if id(d) in visited:
        return
    visited.add(id(d))
    for key, value in d.items():
        new_prefix = f"{prefix}.{key}" if prefix else key
        if isinstance(value, dict):
            traverse_nested_dict(value, new_prefix)
        else:
            print(f"{new_prefix}: {value}")