parsing an empty folder without data raise a ValueError

sensospot_data/__init__.py

@@ -87,6 +87,14 @@ def _parse_recursive(source, outfile, quiet):
     child_outfile = DEFAULT_OUTPUT_FILENAME
     source_path = Path(source)
     folders = (i for i in source_path.iterdir() if i.is_dir())
-    collection = (_parse_one_folder(f, child_outfile, quiet) for f in folders)
-    collected_data = pandas.concat(collection, ignore_index=True).reset_index()
+    non_hidden = (i for i in folders if not i.name.startswith("."))
+    collection = (
+        _parse_one_folder(f, child_outfile, quiet) for f in non_hidden
+    )
+    try:
+        collected_data = pandas.concat(
+            collection, ignore_index=True
+        ).reset_index()
         _output(collected_data, source_path, outfile)
+    except ValueError as e:
+        print(str(e))

sensospot_data/parser.py

@@ -140,10 +140,21 @@ def _sanity_check(data_frame):
 
 
 def parse_folder(folder, quiet=False):
-    """parses all csv files in a folder to one large dataframe"""
+    """parses all csv files in a folder to one large dataframe
+
+    Will raise an ValueError, if no sensospot data could be found in
+    the folder
+
+    folder:  path of folder containing data files
+    quiet:   skip sanity check, defaults to False
+    returns: pandas dataframe with parsed data
+    """
     folder_path = Path(folder)
     file_list = list_csv_files(folder_path)
+    try:
         data_frame = parse_multiple_files(file_list)
+    except ValueError:
+        raise ValueError(f"No sensospot data found in folder '{folder}'")
     data_frame = add_optional_measurement_parameters(data_frame, folder_path)
     if quiet:
         return data_frame