python子类与实例

class A:
    pass

class B(A):
    pass

>>> issubclass(A,B)
False
>>> issubclass(B,A)
True
>>> a = A()
>>> isinstance(a,A)
>>> b = B()
>>> isinstance(b,A)
True

>>> setattr(a,'v1',1)
>>> getattr(a,'v1')
1
>>> hasattr(a,'v2')
False
>>> delattr(a,'v2')

Traceback (most recent call last):
  File "<pyshell#48>", line 1, in <module>
    delattr(a,'v2')
AttributeError: A instance has no attribute 'v2'
>>> delattr(a,'v1')
>>> getattr(a,'v1')//删除了就没有了

Traceback (most recent call last):
  File "<pyshell#50>", line 1, in <module>
    getattr(a,'v1')
AttributeError: A instance has no attribute 'v1'