Update build.py

build.py

@@ -22,13 +22,14 @@ if __name__ == '__main__':
 
         # Swap placholders and write out each version for this class
         for ex_no, d in enumerate(data, start=1):
+            lab2 = lab[:]
             d.update({'lp': unicode(ex_no), 'labno': unicode(i)})
 
             for k, v in d.iteritems():
-                lab = lab.replace(u'$%s$' % (k, ), v)
+                lab2 = lab2.replace(u'$%s$' % (k, ), v)
 
             with open('%s%s.md' % (dist_lp, ex_no, ), 'wb') as labout:
-                labout.write(lab.encode('utf8'))
+                labout.write(lab2.encode('utf8'))
 
             os.system(('pandoc %s%s.md -s -o %s%s.pdf') % (dist_lp, ex_no, dist_lp, ex_no))