为什么“返回自我"返回无? [英] Why does 'return self' return None?

问题描述

我正在尝试在 getTopParent() 中获取链的顶部节点.当我打印出self.name 时，它确实打印出父实例的名称；但是，当我返回 self 时，它返回 None.这是为什么?

I'm trying to get the top node of a chain in getTopParent(). When I print out self.name, it indeed prints out the name of the parent instance; however, when I return self, it returns None. Why is this?

class A:
    def __init__( self, name ):
        self.name = name
        self.owner = None
    def setChild( self, l ):
        l.owner = self
    def getTopParent( self ):
        if( self.owner == None ): # None == top parent
            print( "Got top: %s" % self.name )
            return self
        else:
            print( "checking %s" % self.name )
            self.owner.getTopParent()

a = A( "parent" )
b = A( "child1" )
c = A( "child2" )
d = A( "child3" )
a.setChild( b )
b.setChild( c )
c.setChild( d )

print( d.getTopParent() )
>>> checking child3
    checking child2
    checking child1
    Got top: parent
    None

推荐答案

你需要返回 self.owner.getTopParent()!

在 Python 中，您必须实际使用 return 语句从函数返回某些内容，否则返回 None.

In Python, you must actually use the return statement to return something from a function, otherwise None is returned.

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