No, the replacement is:

try:
   v
except NameError:
   v = 'bla bla'

However, wanting to use this construct is a sign of overly complicated code flow. Usually, you'd do the following:

try:
   v = complicated()
except ComplicatedError: # complicated failed
   v = 'fallback value'

and never be unsure whether v is set or not. If it's one of many options that can either be set or not, use a dictionary and its get method which allows a default value.