Python：如何使用getattr获取对象属性的属性？

Question

我如何评估

a = myobject.id.number

如果myobject为None

，则返回None

内置getattr？也许getattr(myobject, "id.number", None)？

Answer 1

这应该适用于任何深度：

reduce(lambda obj, attr : getattr(obj, attr, None), ("id","num"), myobject)

Answer 2

getattr(getattr(myobject, "id", None), "number", None)

应该有用。

Answer 3

这是一个单行

a = myobject is not None and myobject.id.number or None

它不会检查id是否为None，但这不是原始问题的一部分。

Answer 4

略微过于通用的解决方案，以便查看所有成员：

if myobject and myobject.id and myobject.id.number:
    a = myobject.id.number
else:
    a = None

Answer 5

return myobject.id.number if myobject else None

Answer 6

我的最爱是

from functools import reduce
try:
  a = reduce(getattr, ("id", "number"), myobject)
except AttributeError:
  a = None

或

from operator import attrgetter
try:
  a = attrgetter('id.number')(myobject)
except AttributeError:
  a = None