Update python-markdown to nbextensions config

usability/python-markdown/pymdpreprocessor.py

@@ -0,0 +1,46 @@
+"""This preprocessor replaces Python code in markdowncell with the result
+stored in cell metadata
+"""
+
+#-----------------------------------------------------------------------------
+# Copyright (c) 2014, Juergen Hasch
+#
+# Distributed under the terms of the Modified BSD License.
+#
+#-----------------------------------------------------------------------------
+
+from IPython.nbconvert.preprocessors import *
+import re
+
+class PyMarkdownPreprocessor(Preprocessor):
+
+    def replace_variables(self,source,variables):
+        """
+        Replace {{variablename}} with stored value
+        """
+        try:
+            replaced = re.sub("{{(.*?)}}", lambda m: variables[m.group(1)] , source)
+        except TypeError:
+            replaced = source
+        return replaced
+
+    def preprocess_cell(self, cell, resources, index):
+        """
+        Preprocess cell
+
+        Parameters
+        ----------
+        cell : NotebookNode cell
+            Notebook cell being processed
+        resources : dictionary
+            Additional resources used in the conversion process.  Allows
+            preprocessors to pass variables into the Jinja engine.
+        cell_index : int
+            Index of the cell being processed (see base.py)
+        """
+        if cell.cell_type == "markdown":
+            if hasattr(cell['metadata'], 'variables'):
+                variables = cell['metadata']['variables']
+                if len(variables) > 0:
+                    cell.source = self.replace_variables(cell.source, variables)
+        return cell, resources