类型错误：实例之间不支持'<' - 对象

Question

我正在尝试按名称进行排序，但它键入错误：typeError：'＆lt;'在"人"one_answers"人"的实例之间不支持。你能告诉我问题在哪里吗？这是我的代码。

class Person:
    def __init__(self, name, year_of_birth, degree):
        self.name = name
        self.year_of_birth = year_of_birth
        self.degree = degree
        self.mentor = None
        self.mentees = []
def create_mentorship(mentor, mentee):
    mentee.mentor = mentor
    mentor.mentees.append(mentee)
def get_founder(people):
    for person in people:
        if people[person].mentor == None:
            return people[person]
def print_mentorship_tree(people):
    person = get_founder(people)
    print_mentorship_subtree(person)

def print_mentorship_subtree(person, level=0):
    a = []
    print((" " * level) + person.name +' (' + str(person.year_of_birth) + ')')
    for mentee in person.mentees:
        print_mentorship_subtree(mentee, level + 1)
        a = sorted(person.mentees)
    >>> people = {}
    >>> people['Martin'] = Person('Martin', 1991, 'phd')
    >>> people['Lukas'] = Person('Lukas', 1991, 'phd')
    >>> people['Tom'] = Person('Tom', 1993, 'mgr')
    >>> people['Honza'] = Person('Honza', 1995, 'bc')
    >>> create_mentorship(people['Martin'], people['Tom'])
    >>> create_mentorship(people['Tom'], people['Honza'])
    >>> create_mentorship(people['Martin'], people['Lukas'])
    >>> print_mentorship_tree(people)

错误：

Traceback (most recent call last):
  File "so.py", line 38, in <module>
    print_mentorship_tree(people)
  File "so.py", line 20, in print_mentorship_tree
    print_mentorship_subtree(person)
  File "so.py", line 28, in print_mentorship_subtree
    a = sorted(person.mentees)
TypeError: unorderable types: Person() < Person()

Answer 1

这就是它所说的：您无法对Person对象进行排序。如果您想使用此功能，则必须使用您想到的任何类型标准来定义班级的__lt__操作员 - 也许按名称为字母？

另一种可能性是简单地编写自己的功能，并使用person.mentees.obj_sort调用。

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另外，我不确定为什么这很重要：您从不使用使用此操作的返回值。您将其存储在局部变量a中（顺便说一句，这是一个差的变量名称），并且永远不会使用它。

Answer 2

如何编写自定义密钥函数并将其传递为sorted()参数？

sorted_list = sorted(person.mentees, key=lambda p: p.name)