unify usage of tuple and list (#36368)

* modify format

* modify format

python/paddle/autograd/functional.py

@@ -18,20 +18,7 @@ from ..fluid import framework
 from ..fluid.dygraph import grad
 from ..nn.initializer import assign
 from ..tensor import reshape, zeros_like, to_tensor
-from .utils import _check_tensors, _stack_tensor_or_return_none, _replace_none_with_zero_tensor
-
-
-def to_tensorlist(tl):
-    if not isinstance(tl, list):
-        if isinstance(tl, tuple):
-            tl = list(tl)
-        else:
-            tl = [tl]
-    for t in tl:
-        assert isinstance(t, paddle.Tensor) or t is None, (
-            f'{t} is expected to be paddle.Tensor or None, but found {type(t)}.'
-        )
-    return tl
+from .utils import _tensors, _stack_tensor_or_return_none, _replace_none_with_zero_tensor
 
 
 @contextlib.contextmanager
@@ -98,19 +85,19 @@ def vjp(func, inputs, v=None, create_graph=False, allow_unused=False):
     reverse mode automatic differentiation.
 
     Args:
-        func(Callable): `func` takes as input a tensor or a list
-            of tensors and returns a tensor or a list of tensors.
-        inputs(list[Tensor]|Tensor): used as positional arguments
-            to evaluate `func`. `inputs` is accepted as one tensor
-            or a list of tensors.
-        v(list[Tensor]|Tensor, optional): the cotangent vector
-            invovled in the VJP computation. `v` matches the size
-            and shape of `func`'s output. Default value is None
+        func(Callable): `func` takes as input a tensor or a list/tuple
+            of tensors and returns a tensor or a list/tuple of tensors.
+        inputs(list[Tensor]|tuple[Tensor]|Tensor): used as positional
+            arguments to evaluate `func`. `inputs` is accepted as one
+            tensor or a list of tensors.
+        v(list[Tensor]|tuple[Tensor]|Tensor|None, optional): the
+            cotangent vector invovled in the VJP computation. `v` matches
+            the size and shape of `func`'s output. Default value is None
             and in this case is equivalent to all ones the same size
             of `func`'s output.
-        create_graph(bool, optional): if `True`, gradients can
-            be evaluated on the results. If `False`, taking gradients
-            on the results is invalid. Default value is False.
+        create_graph(bool, optional): if `True`, gradients can be
+            evaluated on the results. If `False`, taking gradients on
+            the results is invalid. Default value is False.
         allow_unused(bool, optional): In case that some Tensors of
             `inputs` do not contribute to the computation of the output.
             If `allow_unused` is False, an error will be raised,
@@ -119,8 +106,9 @@ def vjp(func, inputs, v=None, create_graph=False, allow_unused=False):
 
     Returns:
         output(tuple):
-            func_out: the output of `func(inputs)`
-            vjp(list[Tensor]|Tensor): the pullback results of `v` on `func`
+            func_out(list[Tensor]|tuple[Tensor]|Tensor): the output of
+                `func(inputs)`
+            vjp(list[Tensor]): the pullback results of `v` on `func`
 
     Examples:
       .. code-block:: python
@@ -163,13 +151,13 @@ def vjp(func, inputs, v=None, create_graph=False, allow_unused=False):
         #        [[2., 1.],
         #         [1., 0.]]), None]
     """
-    xs, v = to_tensorlist(inputs), to_tensorlist(v)
+    xs, v = _tensors(inputs, "inputs"), _tensors(v, "v")
 
     with gradient_scope(
             xs, v, create_graph=create_graph,
             allow_unused=allow_unused) as [xs, v, grad_fn, return_fn]:
         outputs = func(*xs)
-        ys = to_tensorlist(outputs)
+        ys = _tensors(outputs, "outputs")
         grads = grad_fn(ys, xs, v)
         outputs, grads = return_fn(outputs), return_fn(grads)
 
@@ -186,16 +174,16 @@ def jvp(func, inputs, v=None, create_graph=False, allow_unused=False):
         **This API is ONLY available in imperative mode.**
 
     Args:
-        func(Callable): `func` takes as input a tensor or a list
-            of tensors and returns a tensor or a list of tensors.
-        inputs(list[Tensor]|Tensor): used as positional arguments
-            to evaluate `func`. `inputs` is accepted as one tensor
-            or a list of tensors.
-        v(list[Tensor]|Tensor, optional): the tangent vector
-            invovled in the JVP computation. `v` matches the size
-            and shape of `inputs`. `v` is Optional if `func` returns
-            a single tensor. Default value is None and in this case
-            is equivalent to all ones the same size of `inputs`.
+        func(Callable): `func` takes as input a tensor or a list/tuple
+            of tensors and returns a tensor or a list/tuple of tensors.
+        inputs(list[Tensor]|tuple[Tensor]|Tensor): used as positional
+            arguments to evaluate `func`. `inputs` is accepted as one
+            tensor or a list/tuple of tensors.
+        v(list[Tensor]|tuple[Tensor]|Tensor|None, optional): the
+            tangent vector invovled in the JVP computation. `v` matches
+            the size and shape of `inputs`. `v` is Optional if `func`
+            returns a single tensor. Default value is None and in this
+            case is equivalent to all ones the same size of `inputs`.
         create_graph(bool, optional): if `True`, gradients can
             be evaluated on the results. If `False`, taking gradients
             on the results is invalid. Default value is False.
@@ -207,8 +195,9 @@ def jvp(func, inputs, v=None, create_graph=False, allow_unused=False):
 
     Returns:
         output(tuple):
-            func_out: the output of `func(inputs)`
-            jvp(list[Tensor]|Tensor): the pullback results of `v` on `func`
+            func_out(list[Tensor]|tuple[Tensor]|Tensor): the output of
+                `func(inputs)`
+            jvp(list[Tensor]): the pullback results of `v` on `func`
 
     Examples:
     .. code-block:: python
@@ -232,13 +221,13 @@ def jvp(func, inputs, v=None, create_graph=False, allow_unused=False):
         #         [0., 0.]])]
 
     """
-    xs, v = to_tensorlist(inputs), to_tensorlist(v)
+    xs, v = _tensors(inputs, "inputs"), _tensors(v, "v")
 
     with gradient_scope(
             xs, v, create_graph=create_graph,
             allow_unused=allow_unused) as [xs, v, grad_fn, return_fn]:
         outputs = func(*xs)
-        ys = to_tensorlist(outputs)
+        ys = _tensors(outputs, "outputs")
         ys_grad = [zeros_like(y) for y in ys]
         xs_grad = grad_fn(ys, xs, ys_grad, create_graph=True)
         ys_grad = grad_fn(xs_grad, ys_grad, v)
@@ -357,8 +346,8 @@ def jacobian(func, inputs, create_graph=False, allow_unused=False):
             #         [0., 0., 0., 2.]]), None))
 
     '''
-    inputs = _check_tensors(inputs, "inputs")
-    outputs = _check_tensors(func(*inputs), "outputs")
+    inputs = _tensors(inputs, "inputs")
+    outputs = _tensors(func(*inputs), "outputs")
     fin_size = len(inputs)
     fout_size = len(outputs)
     flat_outputs = tuple(reshape(output, shape=[-1]) for output in outputs)
@@ -494,7 +483,7 @@ def hessian(func, inputs, create_graph=False, allow_unused=False):
             #         [0., 1., 1., 2.]]), None), (None, None))
 
     '''
-    inputs = _check_tensors(inputs, "inputs")
+    inputs = _tensors(inputs, "inputs")
     outputs = func(*inputs)
     assert isinstance(outputs, paddle.Tensor) and outputs.shape == [
         1

python/paddle/autograd/utils.py

@@ -15,22 +15,20 @@
 import paddle
 
 
-def _check_tensors(in_out_list, name):
-    assert in_out_list is not None, "{} should not be None".format(name)
-
-    if isinstance(in_out_list, (list, tuple)):
-        assert len(in_out_list) > 0, "{} connot be empyt".format(name)
-        for each_var in in_out_list:
+def _tensors(ts, name):
+    if isinstance(ts, (list, tuple)):
+        assert len(ts) > 0, "{} connot be empty".format(name)
+        for each_t in ts:
             assert isinstance(
-                each_var,
-                paddle.Tensor), "Elements of {} must be paddle.Tensor".format(
+                each_t, paddle.Tensor
+            ) or each_t is None, "Elements of {} must be paddle.Tensor or None".format(
                 name)
-        return list(in_out_list)
+        return list(ts)
     else:
         assert isinstance(
-            in_out_list,
-            paddle.Tensor), "{} must be Tensor or list of Tensor".format(name)
-        return [in_out_list]
+            ts, paddle.Tensor
+        ) or ts is None, "{} must be Tensor or list of Tensor".format(name)
+        return [ts]
 
 
 def _stack_tensor_or_return_none(origin_list):

python/paddle/fluid/dygraph/base.py

@@ -456,7 +456,7 @@ def grad(outputs,
             the Tensors whose gradients are not needed to compute. Default None.
 
     Returns:
-        tuple: a tuple of Tensors, whose length is the same as the Tensor number 
+        list: a list of Tensors, whose length is the same as the Tensor number 
         inside `inputs`, and the i-th returned Tensor is the sum of gradients of 
         `outputs` with respect to the i-th `inputs`.
 

python/paddle/fluid/tests/unittests/autograd/test_vjp_jvp.py

@@ -15,7 +15,7 @@
 import unittest
 import paddle
 
-from paddle.autograd.functional import vjp, jvp, to_tensorlist
+from paddle.autograd.functional import vjp, jvp, _tensors
 from paddle import grad, ones_like, zeros_like
 
 
@@ -55,7 +55,7 @@ def nested(x):
 
 
 def make_v(f, inputs):
-    outputs = to_tensorlist(f(*inputs))
+    outputs = _tensors(f(*inputs), "outputs")
     return [ones_like(x) for x in outputs]
 
 

python/paddle/fluid/tests/unittests/autograd/utils.py

@@ -14,7 +14,7 @@
 
 import numpy as np
 import paddle
-from paddle.autograd.functional import _check_tensors
+from paddle.autograd.functional import _tensors
 
 
 def _product(t):
@@ -42,8 +42,8 @@ def _set_item(t, idx, value):
 
 
 def _compute_numerical_jacobian(func, xs, delta, np_dtype):
-    xs = _check_tensors(xs, "xs")
-    ys = _check_tensors(func(*xs), "ys")
+    xs = _tensors(xs, "xs")
+    ys = _tensors(func(*xs), "ys")
     fin_size = len(xs)
     fout_size = len(ys)
     jacobian = list([] for _ in range(fout_size))
@@ -59,11 +59,11 @@ def _compute_numerical_jacobian(func, xs, delta, np_dtype):
             orig = _get_item(xs[j], q)
             x_pos = orig + delta
             xs[j] = _set_item(xs[j], q, x_pos)
-            ys_pos = _check_tensors(func(*xs), "ys_pos")
+            ys_pos = _tensors(func(*xs), "ys_pos")
 
             x_neg = orig - delta
             xs[j] = _set_item(xs[j], q, x_neg)
-            ys_neg = _check_tensors(func(*xs), "ys_neg")
+            ys_neg = _tensors(func(*xs), "ys_neg")
 
             xs[j] = _set_item(xs[j], q, orig)
 
@@ -76,8 +76,8 @@ def _compute_numerical_jacobian(func, xs, delta, np_dtype):
 
 
 def _compute_numerical_hessian(func, xs, delta, np_dtype):
-    xs = _check_tensors(xs, "xs")
-    ys = _check_tensors(func(*xs), "ys")
+    xs = _tensors(xs, "xs")
+    ys = _tensors(func(*xs), "ys")
     fin_size = len(xs)
     hessian = list([] for _ in range(fin_size))
     for i in range(fin_size):