Enhance Check mechanism and Support single tuple/list of fetch_list in Executor (#35726)

* Enhance Check mechanism of fetch_list in Executor

* support single tuple

* fix typo

* fix typo

python/paddle/fluid/executor.py

@@ -833,7 +833,7 @@ class Executor(object):
                     "The item in fetch_list should be str, variable or optimize_op, but recieved %s.",
                     type(item))
 
-        for item in fetch_list:
+        for index, item in enumerate(fetch_list):
             # NOTE(zhiqiu): to support (optimizer_ops, param_and_grads) and optimizer_ops in fetch_list
             # we should handle tuple and list in fetch_list.
             # TODO(zhiqiu): find a better way to handle that.
@@ -841,6 +841,10 @@ class Executor(object):
                 for i in item:
                     _get_targets(_optimize_ops, _fetch_list, i)
             elif isinstance(item, tuple):
+                if not isinstance(item[0], (list, tuple)):
+                    raise TypeError(
+                        "Requires fetch_list[{}][0] shall be one of (list, tuple) when type(fetch_list[{}]) is `tuple`, but received fetch_list[{}][0]'s type is `{}`.".
+                        format(index, index, index, type(item[0]).__name__))
                 for i in item[0]:
                     _get_targets(_optimize_ops, _fetch_list, i)
             else:
@@ -1249,17 +1253,7 @@ class Executor(object):
         if program is None:
             program = default_main_program()
 
-        if fetch_list is not None:
-            if isinstance(fetch_list, Variable) or isinstance(
-                    fetch_list, str) or isinstance(fetch_list,
-                                                   six.string_types):
-                fetch_list = [fetch_list]
-            assert isinstance(fetch_list, tuple) or isinstance(fetch_list, list), \
-                "Currently , The fetch_list type only should be list or tuple, \n"\
-                "but the input type is {}. For more information please refer to \n"\
-                "the executor.run(...).".format(type(fetch_list))
-        else:
-            fetch_list = []
+        fetch_list = self._check_fetch_list(fetch_list)
 
         if isinstance(program, Program) and program._pipeline_opt:
             if "startup_program" in program._pipeline_opt:
@@ -1479,6 +1473,35 @@ class Executor(object):
     def _run_inference(self, exe, feed):
         return exe.run(feed)
 
+    def _check_fetch_list(self, fetch_list):
+        is_fetch_var = lambda var: isinstance(var, (Variable, str, six.string_types))
+        is_tuple_list = lambda var: isinstance(var, (tuple, list))
+
+        if fetch_list is None: return []
+        if is_fetch_var(fetch_list): return [fetch_list]
+
+        assert is_tuple_list(fetch_list), \
+            "Currently , The fetch_list type only should be list or tuple, \n"\
+            "but the input type is {}. For more information please refer to \n"\
+            "the executor.run(...).".format(type(fetch_list))
+
+        res = []
+        for i, var in enumerate(fetch_list):
+            if is_fetch_var(var):
+                res.append(var)
+            # such as [x, 'mean_out', loss]
+            elif is_tuple_list(var):
+                if all(is_fetch_var(v) for v in var):
+                    res.extend(list(var))
+                else:
+                    res.append(var)
+            else:
+                raise TypeError(
+                    "Require fetch_list[{}] 's type shall be one of (Variable, str), but received {}.".
+                    format(i, type(var).__name__))
+
+        return res
+
     def _dump_debug_info(self, program=None, trainer=None):
         with open(str(id(program)) + "_train_desc.prototxt", "w") as fout:
             fout.write(str(trainer))

python/paddle/fluid/tests/unittests/test_executor_check_fetch_list.py

+# Copyright (c) 2021 PaddlePaddle Authors. All Rights Reserved.
+# 
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+# 
+#     http://www.apache.org/licenses/LICENSE-2.0
+# 
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from __future__ import print_function
+
+import unittest
+
+import numpy as np
+import paddle
+import unittest
+
+
+class TestCheckFetchList(unittest.TestCase):
+    def setUp(self):
+        paddle.enable_static()
+        self.feed = {"x": np.array([[0], [0], [1], [0]], dtype='float32')}
+        self.expected = np.array([[0], [1], [0]], dtype='float32')
+        self.build_program()
+        self.exe = paddle.static.Executor(paddle.CPUPlace())
+
+    def build_program(self):
+        main_program = paddle.static.Program()
+        with paddle.static.program_guard(main_program):
+            x = paddle.static.data(name='x', shape=[4, 1], dtype='float32')
+            output = paddle.unique_consecutive(
+                x, return_inverse=True, return_counts=True, axis=0)
+
+        self.main_program = main_program
+        self.fetch_list = output
+
+    def test_with_tuple(self):
+
+        res = self.exe.run(
+            self.main_program,
+            feed=self.feed,
+            fetch_list=[self.fetch_list],  # support single list/tuple
+            return_numpy=True)
+
+        self.assertTrue(np.array_equal(res[0], self.expected))
+
+    def test_with_error(self):
+        with self.assertRaises(TypeError):
+            fetch_list = [23]
+            res = self.exe.run(self.main_program,
+                               feed=self.feed,
+                               fetch_list=fetch_list)
+
+        with self.assertRaises(TypeError):
+            fetch_list = [(self.fetch_list[0], 32)]
+            res = self.exe.run(self.main_program,
+                               feed=self.feed,
+                               fetch_list=fetch_list)
+
+
+if __name__ == '__main__':
+    unittest.main()