Polish code

test=develop

python/paddle/fluid/optimizer.py

@@ -94,6 +94,11 @@ class Optimizer(object):
         if imperative_base.enabled():
             # create learning rate Variable
             if isinstance(self._learning_rate, float):
+                lr = self._global_learning_rate()
+
+                if isinstance(lr, framework.Variable):
+                    return
+                else:
                     self._learning_rate_map[framework.default_main_program(
                     )] = layers.create_global_var(
                         name=unique_name.generate("learning_rate"),
@@ -114,11 +119,12 @@ class Optimizer(object):
 
             if isinstance(lr, framework.Variable):
                 return
-
+            else:
                 if not isinstance(self._learning_rate, float):
                     raise TypeError(
                         "learning rate variable is create outside optimizer,"
-                    "can not create new learning rate variable for new program")
+                        "can not create new learning rate variable for new program"
+                    )
 
             # create learning rate in the current main program
             self._learning_rate_map[framework.default_main_program(