minrk · February 28, 2012 22:47 · May 31, 2012 · Feb 28, 2012
diff --git a/downgradenb.py b/downgradenb.py
@@ -12,8 +12,8 @@ def heading_to_md(cell):
     level = cell.pop('level', 1)
     cell.source = '#'*level + ' ' + cell.source
 
-def txt_to_md(cell):
-    """let plaintext passthrough as markdown"""
+def raw_to_md(cell):
+    """let raw passthrough as markdown"""
     cell.cell_type = "markdown"
 
 def downgrade(nb):
@@ -25,8 +25,8 @@ def downgrade(nb):
         for cell in ws.cells:
             if cell.cell_type == 'heading':
                 heading_to_md(cell)
-            elif cell.cell_type == 'plaintext':
-                txt_to_md(cell)
+            elif cell.cell_type == 'raw':
+                raw_to_md(cell)
     return nb
 
 def downgrade_ipynb(fname):

diff --git a/downgradenb.py b/downgradenb.py
@@ -0,0 +1,43 @@
+"""Simple utility script for semi-gracefully downgrading v3 notebooks to v2"""
+
+import io
+import os
+import sys
+
+from IPython.nbformat import current
+
+def heading_to_md(cell):
+    """turn heading cell into corresponding markdown"""
+    cell.cell_type = "markdown"
+    level = cell.pop('level', 1)
+    cell.source = '#'*level + ' ' + cell.source
+
+def txt_to_md(cell):
+    """let plaintext passthrough as markdown"""
+    cell.cell_type = "markdown"
+
+def downgrade(nb):
+    """downgrade a v3 notebook to v2"""
+    if nb.nbformat != 3:
+        return nb
+    nb.nbformat = 2
+    for ws in nb.worksheets:
+        for cell in ws.cells:
+            if cell.cell_type == 'heading':
+                heading_to_md(cell)
+            elif cell.cell_type == 'plaintext':
+                txt_to_md(cell)
+    return nb
+
+def downgrade_ipynb(fname):
+    base, ext = os.path.splitext(fname)
+    newname = base+'.v2'+ext
+    print "downgrading %s -> %s" % (fname, newname)
+    with io.open(fname, 'r', encoding='utf8') as f:
+        nb = current.read(f, 'json')
+    nb = downgrade(nb)
+    with open(newname, 'w') as f:
+        current.write(nb, f, 'json')
+
+if __name__ == '__main__':
+    map(downgrade_ipynb, sys.argv[1:])