@attr.s
class A(object):
    p=attr.ib(default='old')

@attr.s
class B(A):
    p=attr.ib(default='new')

B().p

Traceback (most recent call last):
  File "E:/D/OneDrive/PyCharm/attrs_test/01.py", line 44, in <module>
    class B(A):
  File "E:\D\OneDrive\Miniconda3\envs\dev\lib\site-packages\attr\_make.py", line 391, in attributes
    return wrap(maybe_cls)
  File "E:\D\OneDrive\Miniconda3\envs\dev\lib\site-packages\attr\_make.py", line 364, in wrap
    cls = _add_init(cls, effectively_frozen)
  File "E:\D\OneDrive\Miniconda3\envs\dev\lib\site-packages\attr\_make.py", line 569, in _add_init
    bytecode = compile(script, unique_filename, "exec")
  File "<attrs generated init 6e95dcc9478c7a8b8784f6244afbff55f563f7c6>", line 1
SyntaxError: duplicate argument 'p' in function definition