add minor-version support to .py export

IPython/nbformat/current.py

@@ -55,13 +55,18 b' def parse_json(s, **kwargs):'
 
 def parse_py(s, **kwargs):
     """Parse a string into a (nbformat, string) tuple."""
-    pattern = r'# <nbformat>(?P<nbformat>\d+)</nbformat>'
+    nbf = current_nbformat
+    nbm = current_nbformat_minor
+    
+    pattern = r'# <nbformat>(?P<nbformat>\d+[\.\d+]*)</nbformat>'
     m = re.search(pattern,s)
     if m is not None:
-        nbf = int(m.group('nbformat'))
-    else:
-        nbf = current_nbformat
-    return nbf, s
+        digits = m.group('nbformat').split('.')
+        nbf = int(digits[0])
+        if len(digits) > 1:
+            nbm = int(digits[1])
+
+    return nbf, nbm, s
 
 
 def reads_json(s, **kwargs):
@@ -87,8 +92,7 b' def writes_json(nb, **kwargs):'
 
 def reads_py(s, **kwargs):
     """Read a .py notebook from a string and return the NotebookNode object."""
-    nbf, s = parse_py(s, **kwargs)
-    nbf = nbf
+    nbf, nbm, s = parse_py(s, **kwargs)
     if nbf == 2:
         nb = v2.to_notebook_py(s, **kwargs)
     elif nbf == 3:

IPython/nbformat/v3/nbpy.py

@@ -20,7 +20,7 b' import re'
 from .rwbase import NotebookReader, NotebookWriter
 from .nbbase import (
     new_code_cell, new_text_cell, new_worksheet,
-    new_notebook, new_heading_cell, nbformat
+    new_notebook, new_heading_cell, nbformat, nbformat_minor,
 )
 
 #-----------------------------------------------------------------------------
@@ -152,7 +152,10 b' class PyWriter(NotebookWriter):'
 
     def writes(self, nb, **kwargs):
         lines = [u'# -*- coding: utf-8 -*-']
-        lines.extend([u'# <nbformat>%i</nbformat>' % nbformat,''])
+        lines.extend([
+            u'# <nbformat>%i.%i</nbformat>' % (nbformat, nbformat_minor),
+            u'',
+        ])
         for ws in nb.worksheets:
             for cell in ws.cells:
                 if cell.cell_type == u'code':

IPython/nbformat/v3/tests/nbexamples.py

@@ -6,7 +6,7 b' from base64 import encodestring'
 from ..nbbase import (
     NotebookNode,
     new_code_cell, new_text_cell, new_worksheet, new_notebook, new_output,
-    new_metadata, new_author, new_heading_cell, nbformat
+    new_metadata, new_author, new_heading_cell, nbformat, nbformat_minor
 )
 
 # some random base64-encoded *bytes*
@@ -108,7 +108,7 b' nb0 = new_notebook('
 )
 
 nb0_py = u"""# -*- coding: utf-8 -*-
-# <nbformat>%i</nbformat>
+# <nbformat>%i.%i</nbformat>
 
 # <htmlcell>
 
@@ -148,6 +148,6 b' b = 5'
 
 print "ünîcødé"
 
-""" % nbformat
+""" % (nbformat, nbformat_minor)