getattr

class Persion:
    def __init__(self, arms, head):
        self.arms = arms
        self.head = head
        
p1 = Persion(2, 1)
print(getattr(p1, 'arms'))
print(getattr(p1, 'arm', 3))
print(getattr(p1, 'arm'))

第7行，输出2

第8行，输出3

第9行，报错：

  File "getattrtest.py", line 9, in <module>
    getattr(p1, 'arm')
AttributeError: 'Persion' object has no attribute 'arm'