Return a weak reference to \var{object}. The original object can be
retrieved by calling the reference object if the referent is still
alive; if the referent is no longer alive, calling the reference
- object will cause \code{None} to be returned. If \var{callback} is
+ object will cause \constant{None} to be returned. If \var{callback} is
provided and not \constant{None},
it will be called when the object is about to be
finalized; the weak reference object will be passed as the only
\end{verbatim}
If the referent no longer exists, calling the reference object returns
-\code{None}:
+\constant{None}:
\begin{verbatim}
>>> del o, o2