在嵌套字典中查找键

Question

我正在尝试在嵌套字典中查找键：

mydict = {
    ('Geography', 1): {},
    ('Languages', 2): {
        ('English', 3): {
            ('Grammar', 6): {
                ('new', 10):{},
                ('old', 11): {}
            }
        },
        ('Spanish', 4): {},
        ('French', 5):  {
            ('Grammar', 7): {}
        },
        ('Dutch', 8): {
            ('Grammar', 9): {
                ('new', 12):{}
            }
        }
    }
}

所以我在字典中循环查找键 ('Grammar', 9) 例如：

def _loop(topic, topics_dict):
    if (topic[0], topic[1]) in topics_dict.keys():
        return topics_dict[(topic[0], topic[1])]
    else:
        for k, v in topics_dict.items():
            if v != {}:
                return _loop(topic, v)

topic = ('Grammar', 9)
trim_mydict = _loop(topic, mydict)
print(trim_mydict)

但是，事实上，它returns None 而不是 {('new', 12):{}}

我已经检查了这个线程 (Finding a key recursively in a dictionary)，但我似乎在做同样的事情...

Answer 1

当你 return 在循环中没有条件时，它只有 return 是第一个结果，即使它是 None。我添加了这样的支票：

mydict = {
    ('Geography', 1): {},
    ('Languages', 2): {
        ('English', 3): {
            ('Grammar', 6): {
                ('new', 10):{},
                ('old', 11): {}
            }
        },
        ('Spanish', 4): {},
        ('French', 5):  {
            ('Grammar', 7): {}
        },
        ('Dutch', 8): {
            ('Grammar', 9): {
                ('new', 10):{}
            }
        }
    }
}


def _loop(topic, topics_dict):
    if (topic[0], topic[1]) in topics_dict.keys():
        return topics_dict[(topic[0], topic[1])]
    else:
        for k, v in topics_dict.items():
            if v != {}:
                if (result := _loop(topic, v)) is not None:
                    return result

topic = ('Grammar', 9)
trim_mydict = _loop(topic, mydict)
print(trim_mydict)

>>> {('new', 10): {}}

在嵌套字典中查找键

Finding key in a Nested dictionary

python

nested-loops