[Dy2stat]Fix Python Version compatibility of dict.iteritems (#26778)

* Fix Python Version compatibility

* add import six

python/paddle/fluid/dygraph/dygraph_to_static/function_spec.py

@@ -296,7 +296,7 @@ def convert_to_input_spec(inputs, input_spec):
     elif isinstance(input_spec, dict):
         input_with_spec = {}
         check_type_and_len(inputs, input_spec, True)
-        for name, input in inputs.items():
+        for name, input in six.iteritems(inputs):
             if name in input_spec:
                 input_with_spec[name] = convert_to_input_spec(input,
                                                               input_spec[name])

python/paddle/fluid/dygraph/dygraph_to_static/ifelse_transformer.py

@@ -14,6 +14,7 @@
 
 from __future__ import print_function
 
+import six
 import copy
 from collections import defaultdict
 
@@ -230,7 +231,7 @@ class NameVisitor(gast.NodeVisitor):
         return False
 
     def _update_name_ids(self, new_name_ids):
-        for name_id, ctxs in new_name_ids.items():
+        for name_id, ctxs in six.iteritems(new_name_ids):
             self.name_ids[name_id] = ctxs + self.name_ids[name_id]
 
 
@@ -250,7 +251,7 @@ def parse_cond_args(var_ids_dict, return_ids=None, ctx=gast.Load):
     """
 
     name_ids = [
-        var_id for var_id, var_ctx in var_ids_dict.items()
+        var_id for var_id, var_ctx in six.iteritems(var_ids_dict)
         if isinstance(var_ctx[0], ctx)
     ]
     if return_ids:
@@ -341,7 +342,7 @@ def parse_cond_return(parent_vars_dict, if_vars_dict, else_vars_dict,
 
     def _vars_with_store(ids_dict):
         vars = []
-        for k, ctxs in ids_dict.items():
+        for k, ctxs in six.iteritems(ids_dict):
             if _is_return_var(ctxs):
                 vars.append(k)
         return vars
@@ -353,7 +354,7 @@ def parse_cond_return(parent_vars_dict, if_vars_dict, else_vars_dict,
 
     def _vars_loaded_before_store(ids_dict):
         new_dict = defaultdict(list)
-        for k, ctxs in ids_dict.items():
+        for k, ctxs in six.iteritems(ids_dict):
             for ctx in ctxs:
                 if isinstance(ctx, gast.Load):
                     new_dict[k].append(ctx)

python/paddle/fluid/dygraph/dygraph_to_static/partial_program.py

@@ -15,6 +15,7 @@
 from __future__ import print_function
 import numpy as np
 import logging
+import six
 
 from paddle.fluid import log_helper
 from paddle.fluid import framework, backward, core
@@ -334,7 +335,7 @@ class PartialProgramLayer(layers.Layer):
             param_and_buffer_names_set.add(var.name)
 
         for block in main_program.blocks:
-            for name, var in block.vars.items():
+            for name, var in six.iteritems(block.vars):
                 if isinstance(var, framework.Parameter):
                     if name not in param_and_buffer_names_set:
                         raise ValueError(

python/paddle/fluid/dygraph/dygraph_to_static/program_translator.py

@@ -617,7 +617,7 @@ class ProgramCache(object):
         return len(self._caches)
 
     def concrete_programs(self):
-        return [cp for key, (cp, _) in self._caches.iteritems()]
+        return [cp for key, (cp, _) in six.iteritems(self._caches)]
 
 
 def synchronized(func):

python/paddle/fluid/dygraph/dygraph_to_static/utils.py

@@ -493,7 +493,7 @@ def recover_globals_attribute(src_obj, dst_obj):
     src_globals = getattr(src_obj, attr_name, {})
     dst_globals = getattr(dst_obj, attr_name, {})
 
-    for k, v in src_globals.items():
+    for k, v in six.iteritems(src_globals):
         # ignore builtin attribute.
         if not (k.startswith('__') and k.endswith('__')):
             dst_globals[k] = v

python/paddle/fluid/dygraph/jit.py

@@ -754,7 +754,7 @@ def save(layer, model_path, input_spec=None, configs=None):
     # saved to inference program may not need by dygraph Layer, 
     # we only record the state_dict variable's structured name
     state_names_dict = dict()
-    for structured_name, var in layer.state_dict().items():
+    for structured_name, var in six.iteritems(layer.state_dict()):
         state_names_dict[var.name] = structured_name
 
     # 3. share parameters from Layer to scope & record var info

python/paddle/fluid/tests/unittests/dygraph_to_static/test_declarative.py

@@ -191,6 +191,7 @@ class TestDifferentInputSpecCacheProgram(unittest.TestCase):
             out_1 = foo(to_variable(x_data), to_variable(y_data))
             self.assertTrue(np.allclose(x_data + y_data, out_1.numpy()))
             self.assertTrue(len(foo.program_cache) == 1)
+            self.assertTrue(len(foo.program_cache.concrete_programs()) == 1)
 
             # [16, 10] + [10] (numpy)
             out_2 = foo(to_variable(x_data), y_data)