support minus-int idx to LayerList

[lyuwenyu]

PR types

New features

PR changes

APIs

Describe

• support minux-idx for LayerList
• __getitem__
• __setitem__
• __del__

Before

• getitem problem
• setitem problem

will get surprising result here

In [80]: mm = nn.LayerList([nn.Conv2D(2, 2, 2, 2), nn.Linear(10, 10)])

In [81]: mm[-1]
---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-81-0325fd583382> in <module>
----> 1 mm[-1]

~/opt/anaconda3/lib/python3.8/site-packages/paddle/fluid/dygraph/container.py in __getitem__(self, idx)
    218             return self.__class__(list(self._sub_layers.values())[idx])
    219         else:
--> 220             return self._sub_layers[str(idx)]
    221 
    222     def __setitem__(self, idx, sublayer):

KeyError: '-1'

In [82]: mm[-1] = nn.ReLU()

In [83]: mm
Out[83]: 
LayerList(
  (0): Conv2D(2, 2, kernel_size=[2, 2], stride=[2, 2], data_format=NCHW)
  (1): Linear(in_features=10, out_features=10, dtype=float32)
  (-1): ReLU()
)

After

In [74]: mm = LayerList([nn.Conv2D(2, 2, 2, 2), nn.Linear(10, 10), nn.ReLU()])

In [75]: mm[-1]
Out[75]: ReLU()

In [76]: mm[-1] = nn.Sigmoid()

In [77]: mm
Out[77]: 
LayerList(
  (0): Conv2D(2, 2, kernel_size=[2, 2], stride=[2, 2], data_format=NCHW)
  (1): Linear(in_features=10, out_features=10, dtype=float32)
  (2): Sigmoid()
)

In [78]: del mm[-1]

In [79]: mm
Out[79]: 
LayerList(
  (0): Conv2D(2, 2, kernel_size=[2, 2], stride=[2, 2], data_format=NCHW)
  (1): Linear(in_features=10, out_features=10, dtype=float32)
)

[paddle-bot-old]

Thanks for your contribution!
Please wait for the result of CI firstly. See Paddle CI Manual for details.

[qingqing01]

LGTM

[qingqing01]

LGTM. @phlrain Please help to look

[saxon-zh]

LGTM

[jzhang533]

lgtm