fix bug that tuple(Variable) is converted to list(Variable) uncorrectly (#21687)

python/paddle/fluid/framework.py

@@ -1814,8 +1814,8 @@ class Operator(object):
                                     "The type of '%s' in operator %s should be "
                                     "one of [basestring(), str, Varibale] in python2, "
                                     "or one of [str, bytes, Variable] in python3."
-                                    "but received : " % (in_proto.name, type),
-                                    arg)
+                                    "but received : %s" %
+                                    (in_proto.name, type, arg))
                         self.desc.set_input(in_proto.name, in_arg_names)
                     else:
                         self.desc.set_input(in_proto.name, [])

python/paddle/fluid/layers/nn.py

@@ -12280,16 +12280,18 @@ def py_func(func, x, out, backward_func=None, skip_vars_in_backward_input=None):
         x = []
     elif isinstance(x, Variable):
         x = [x]
-    elif not isinstance(x, (list, tuple)):
+    elif isinstance(x, tuple):
+        x = list(x)
+    elif not isinstance(x, (list, tuple, Variable)):
         raise TypeError('Input must be Variable/list(Variable)/tuple(Variable)')
 
     if out is None:
         out_list = []
     elif isinstance(out, Variable):
         out_list = [out]
-    elif isinstance(out, (list, tuple)):
-        out_list = out
-    else:
+    elif isinstance(out, tuple):
+        out_list = list(out)
+    elif not isinstance(x, (list, tuple, Variable)):
         raise TypeError(
             'Output must be Variable/list(Variable)/tuple(Variable)')