Python in a Nutshell

Name

ref

Synopsis

ref(x[,f])

Returns a weak reference w of type ReferenceType, with object x as the target. w is callable: calling w ( ) returns x if x is still alive, otherwise w ( ) returns None. w is hashable if x is hashable. You can compare weak references for equality (= =, !=), but not for order (<, >, <=, >=). Two weak references x and y are equal if their targets are alive and equal, or if x is y. If f is present, it must be callable with one argument, and is the finalization callback for w (i.e., right before finalizing x, Python calls f ( w )). Note that when f is called, x is no longer reachable from w.