Python 使用递归查找嵌套dict的值并返回dict的键

我有一个练习，其中生日字典如下：

    birthdays = 
    {"Anne": {"month":"Jan","day":"27"},
    "Mike":{"month":"Feb","day":"13"},
    "Nicolas":{"month":"Jun","day":14}, 
    "Marta": {"month":"Jan","day":16}}

问题是定义一个函数，给定一个月，该函数将打印出该月所有生日的人的列表，以及日期

以下是到目前为止我得到的信息：

    def birthbymonth(book, month):
        for k,v in book.items():
            if isinstance(v, dict):
                birthbymonth(v,month)           
            else:
                if month == v:
                    print(book)

当称为birthbymonth（生日，“Jan”）时，打印：

---

但是我不知道如何打印那些有生日的人的名字。

我看不出有任何理由在这里使用递归

def birthbymonth(book, month):
    for person,birthday in book.items():
        if birthday['month'] == month:
            print('{}: {} {}'.format(person, birthday['month'], birthday['day']))

---

正如其他人指出的，不需要递归。相反，请使用列表：

birthdays = {"Anne": {"month":"Jan","day":"27"},
"Mike":{"month":"Feb","day":"13"},
"Nicolas":{"month":"Jun","day":14}, 
"Marta": {"month":"Jan","day":16}}
def dates(birthdays, month):
   return ["{}: {}".format(a, b['day']) for a, b in birthdays.items() if b['month'] == month]

print(dates(birthdays, 'Jan'))

输出：

['Marta: 16', 'Anne: 27']

---

如果您真的想使用递归（不推荐用于此问题），可以对现有代码进行一些修改：

birthdays = {
    "Anne": {"month":"Jan","day":27},
    "Mike": {"month":"Feb","day":13},
    "Nicolas": {"month":"Jun","day":14},
    "Marta": {"month":"Jan","day":16}
}

def birthbymonth(book, month):
    names = []
    for k,v in book.items():
        if isinstance(v, dict):
            names += [(k, book[k]["day"])] if birthbymonth(v,month) is True else []
        else:
            if month == v:
                return True
    return names

print(birthbymonth(birthdays, 'Jan'))
#[('Marta', 16), ('Anne', 27)]

这里有一个解决方案：

birthdays = {"Anne": {"month":"Jan","day":"27"},
             "Mike": {"month":"Feb","day":"13"},
             "Nicolas": {"month":"Jun","day":14}, 
             "Marta": {"month":"Jan","day":16}}

{k: v['day'] for k, v in birthdays.items() if v['month']=='Jan'}

# {'Anne': '27', 'Marta': 16}

birthdays = {"Anne": {"month":"Jan","day":"27"},
             "Mike": {"month":"Feb","day":"13"},
             "Nicolas": {"month":"Jun","day":14}, 
             "Marta": {"month":"Jan","day":16}}

{k: v['day'] for k, v in birthdays.items() if v['month']=='Jan'}

# {'Anne': '27', 'Marta': 16}