Make operation optional, return results from __call__

cli.py

@@ -84,4 +84,4 @@ if __name__ == '__main__':
         operation = checkname
 
     # do what needs to be done
-    Normalisename(operation, args.separator, whitelist)(args.files)
+    Normalisename(args.separator, whitelist, operation)(args.files)

normalisename.py

@@ -7,10 +7,11 @@ from unidecode import unidecode
 
 
 class Normalisename:
-    def __init__(self, operation, separator, whitelist):
-        self._operation, self.operation = None, operation
+    def __init__(self, separator, whitelist, operation=None):
         self._separator = separator
         self._whitelist = set(whitelist)
+        self._operation = None
+        self.operation = operation or self.noop
 
     @property
     def operation(self):
@@ -22,6 +23,10 @@ class Normalisename:
             raise ValueError('Operation must be callable!')
         self._operation = value
 
+    @staticmethod
+    def noop(*_):
+        pass
+
     @property
     def separator(self):
         return self._separator
@@ -32,15 +37,13 @@ class Normalisename:
 
     def __call__(self, path_or_paths):
         if isinstance(path_or_paths, str):
-            self.normalise(path_or_paths)
-        elif isinstance(path_or_paths, Iterable):
-            self.normalise_all(path_or_paths)
-        else:
-            raise ValueError('Argument must be str Iterable[str]!')
+            return self.normalise(path_or_paths)
+        if isinstance(path_or_paths, Iterable):
+            return self.normalise_all(path_or_paths)
+        raise ValueError('Argument must be str Iterable[str]!')
 
     def normalise_all(self, paths):
-        for path in paths:
-            self.normalise(path)
+        return [self.normalise(path) for path in paths]
 
     def normalise(self, path):
         directory = dirname(path)
@@ -48,6 +51,7 @@ class Normalisename:
         normalpath = joinpath(directory, self.normalname(filename))
         if path != normalpath:
             self.operation(path, normalpath)  # pylint: disable=not-callable
+        return normalpath
 
     def check_normal(self, path):
         filename = basename(path)