Ability to detect wrong output directory

script_mac.py

@@ -306,7 +306,10 @@ def compute_macs(args):
     MODEL_NAME = params['chart_file'].split('/')[-1][:-4]
 
     # FILES
-    CAM_FILE_PREFIX   = params['output'] + MODEL_NAME + \
+    # Add trailing '/' if not present
+    output = params['output'] if params['output'][-1] == '/' \
+                else params['output'] + '/'
+    CAM_FILE_PREFIX   = output + MODEL_NAME + \
                         '_' + params['final_prop'] + '_cam'
     # cam_file
     cam_file          = CAM_FILE_PREFIX + ".txt"
@@ -345,6 +348,25 @@ def args_to_param(args):
     return {k: v for k, v in vars(args).items() if k != 'func'}
 
 
+class readable_dir(argparse.Action):
+    """
+    http://stackoverflow.com/questions/11415570/directory-path-types-with-argparse
+    """
+
+    def __call__(self, parser, namespace, values, option_string=None):
+        prospective_dir = values
+
+        if not os.path.isdir(prospective_dir):
+            raise argparse.ArgumentTypeError(
+                "readable_dir:{0} is not a valid path".format(prospective_dir))
+
+        if os.access(prospective_dir, os.R_OK):
+            setattr(namespace, self.dest, prospective_dir)
+        else:
+            raise argparse.ArgumentTypeError(
+                "readable_dir:{0} is not a readable dir".format(prospective_dir))
+
+
 if __name__ == "__main__":
 
     # parser configuration
@@ -367,7 +389,8 @@ if __name__ == "__main__":
     parser_input_file.add_argument('--steps', type=int, nargs='?', default=10)
     parser_input_file.add_argument('--start_prop', nargs='?', default=None)
     parser_input_file.add_argument('--inv_prop', nargs='?', default=None)
-    parser_input_file.add_argument('--output', nargs='?', default='result/')
+    parser_input_file.add_argument('--output', action=readable_dir, nargs='?',
+                                   default='result/')
     parser_input_file.set_defaults(func=compute_macs)