python 3 question:

how can you initialize a list to be used recursively(aka to be preserved) without declaring it as a mutable default argument when using recursion:

eg. instead of this:

def my_move(yeah,blah=[])

I want this to work recursively:

def my_move(yeah,blah=None)

if blah is None:

blah=[]

except i want it to keep the list after the first round and not keep replacing it. Thanks