optimize code

Author: jacquesqiao

python/paddle/fluid/optimizer.py

@@ -38,13 +38,13 @@ class Optimizer(object):
     def __init__(self, learning_rate, global_step=None, regularization=None):
         if not isinstance(learning_rate, float) and \
                 not isinstance(learning_rate, framework.Variable):
-            raise ValueError("learning rate should be float or Variable")
+            raise TypeError("learning rate should be float or Variable")
         self._global_step = global_step
         self.regularization = regularization
         self._learning_rate = learning_rate
         # each program should have a independent learning rate
         # program -> Variable(learning_rate)
-        self._learning_rate_map = defaultdict(lambda: None)
+        self._learning_rate_map = dict()
         if isinstance(self._learning_rate, framework.Variable):
             self._learning_rate_map[framework.default_main_program(
             )] = self._learning_rate
@@ -62,7 +62,7 @@ def _create_global_learning_rate(self):
             return
         else:
             if not isinstance(self._learning_rate, float):
-                raise ValueError(
+                raise TypeError(
                     "learning rate variable is create outside optimizer,"
                     "can not create new learning rate variable for new program")
 
@@ -82,7 +82,7 @@ def global_learning_rate(self, program=None):
         """
         if program is None:
             program = framework.default_main_program()
-        return self._learning_rate_map[program]
+        return self._learning_rate_map.get(program, None)
 
     def _append_optimize_op(self, block, param_and_grad):
         """ append optimize operator to block and return all the added optimize_op