python appengine badkeyerror at paulcarvill.com, the home of Paul Carvill on the web

This drove me nuts an hour tonight. If you’re trying to get an entity key using something like:

yourKey = someString
candidate = Candidate( key=db.Key(yourKey) )

and you get a BadKeyError, it’s because the string you’re sending in isn’t the right length. Also, AppEngine doesn’t return None from the Key method but instead returns a BadKeyError exception. You can handle this by doing:

yourKey = someString
try:
   candidate = Candidate( key=db.Key(yourKey) )
except db.BadKeyError:
   # handle the exception here