add clean checkpoint

Author: seiriosPlus

python/paddle/fluid/io.py

@@ -529,6 +529,19 @@ def load_checkpoint(executor, checkpoint_dir=None, main_program=None):
         filename=None)
 
 
+def clean_checkpoint(checkpoint_dir, delete_dir=False):
+    """
+    clean the checkpoint dir, when the train exits normally, the trainer will call clean_checkpoint to delete checkpoint directory saved before.
+    delete_dir only works when the directory is empty, otherwise, OSError is raised.  
+    """
+    if checkpoint_dir is None:
+        checkpoint_dir = os.getcwd()
+    _lru_delete(checkpoint_dir, max_num_checkpoints=0)
+
+    if delete_dir and not os.listdir(checkpoint_dir):
+        os.rmdir(checkpoint_dir)
+
+
 def _get_serial_dir(serial, checkpoint_dir):
     serial_folder = CHECKPOINT_PREFIX + CHECKPOINT_SEPARATOR + str(serial)
     return os.path.join(checkpoint_dir, serial_folder)