Merge pull request #1042 from afeld/patch-1

simplify the function signature for preprocess()

nbconvert/preprocessors/execute.py

@@ -371,7 +371,7 @@ def setup_preprocessor(self, nb, resources, km=None, **kwargs):
                 for attr in ['nb', 'km', 'kc']:
                     delattr(self, attr)
 
-    def preprocess(self, nb, resources, km=None):
+    def preprocess(self, nb, resources=None, km=None):
         """
         Preprocess notebook executing each code cell.
 
@@ -381,7 +381,7 @@ def preprocess(self, nb, resources, km=None):
         ----------
         nb : NotebookNode
             Notebook being executed.
-        resources : dictionary
+        resources : dictionary (optional)
             Additional resources used in the conversion process. For example,
             passing ``{'metadata': {'path': run_path}}`` sets the
             execution path to ``run_path``.
@@ -397,6 +397,9 @@ def preprocess(self, nb, resources, km=None):
             Additional resources used in the conversion process.
         """
 
+        if not resources:
+            resources = {}
+
         with self.setup_preprocessor(nb, resources, km=km):
             self.log.info("Executing notebook with kernel: %s" % self.kernel_name)
             nb, resources = super(ExecutePreprocessor, self).preprocess(nb, resources)