Python:家族级

Question

我正在实现一个带有参数名称、职位和 child 的“人”类。函数“desc”应返回家谱下的人员列表。

到目前为止，我已经这样做了:

class Person():
    def __init__(self, name, title, children=None):
        self.name = name
        self.title = title
        if children is None:
            self.children = []
        else:
            self.children = children


    def desc(self):
        self.out = []
        if self.children:
            for kid in self.children:
                self.out.append(kid)
            return self.out


p1 = Person("p1", "test")
p2 = Person("p2", "test", children = [p1])
p3 = Person("p3", "test")
p4 = Person("p4", "test", children = [p2, p3])
p5 = Person("p5", "boss", children = [p4])
print [person.title for person in p5.desc()]
# desired output:
# ['test', 'test', 'test','test']
print [person.name for person in p5.desc()]
# desired output:
# ['p4', 'p2', 'p1', 'p3']

但我的实际输出看起来并不像期望的那样。所以，我的问题是:你将如何拯救 children ？在一个简单的列表中？问题显然出在 def desc() 中。感谢您的帮助!

Answer 1

你必须递归 children列表:

def desc(self):
    out = []
    for kid in self.children:
        out.append(kid)
        out.extend(kid.desc())
    return out

这使用了 desc()当前对象上的方法，然后在每个列出的子对象上调用相同的方法以扩展当前结果列表。这一直持续到遇到没有 child 的对象。

请注意 out不需要是实例的属性；我保留了一个局部变量。

这会产生您预期的输出:

>>> class Person():
...     def __init__(self, name, title, children=None):
...         self.name = name
...         self.title = title
...         if children is None:
...             self.children = []
...         else:
...             self.children = children
...     def desc(self):
...         out = []
...         for kid in self.children:
...             out.append(kid)
...             out.extend(kid.desc())
...         return out
... 
>>> p1 = Person("p1", "test")
>>> p2 = Person("p2", "test", children = [p1])
>>> p3 = Person("p3", "test")
>>> p4 = Person("p4", "test", children = [p2, p3])
>>> p5 = Person("p5", "boss", children = [p4])
>>> print [person.title for person in p5.desc()]
['test', 'test', 'test', 'test']
>>> print [person.name for person in p5.desc()]
['p4', 'p2', 'p1', 'p3']

所以 p5.desc()添加 p4到 out列表，然后用 p4.desc() 的结果扩展列表. p4.desc()添加 p2到它的本地out列表，用 p2.desc() 的结果扩展它, 然后添加 p3至 out并用 p3.desc() 扩展它等