fix

python/paddle/fluid/layers/nn.py

@@ -26,7 +26,7 @@ from ..initializer import Normal, Constant
 from ..framework import Variable, OpProtoHolder
 from ..param_attr import ParamAttr
 from .layer_function_generator import autodoc, templatedoc, _generate_doc_string_
-from .tensor import concat
+from .tensor import concat, assign
 from . import utils
 from .. import unique_name
 from functools import reduce

python/paddle/fluid/layers/tensor.py

@@ -310,7 +310,10 @@ def assign(input, output=None, init_once=False):
     if output is None:
         if init_once:
             output = helper.create_parameter(
-                attr=ParamAttr(), shape=input.shape, dtype=input.dtype)
+                attr=ParamAttr(),
+                shape=input.shape,
+                dtype=input.dtype,
+                default_initializer=Constant(0.0))
         else:
             output = helper.create_variable_for_type_inference(
                 dtype=input.dtype)