Please avoid code like this:
try:
some code
except: # bad
more code
try:
return self.__coordinate_ring
except (AttributeError, other exceptions), msg: # Good
more code to compute something
except is to list all the exceptions
that are caught as a tuple, followed by an error message.
If you don't have any exceptions explicitly listed (as a tuple), your
code will catch absolutely anything, including ctrl-C and alarms,
and this will lead to confusion. Also, this might catch real errors which
should be propagated to the user.
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