What use is '() here?

[Robert]

Hi,

Thanks Ian for replying to my previous post. Here is a further question on
the 'return' line below.




import collections
import pickle
class C(collections.defaultdict):
     def __init__(self):
         collections.defaultdict.__init__(self, list)
     def __reduce__(self):
         t = collections.defaultdict.__reduce__(self)
         return (t[0], ()) + t[2:]
         
         
c=C()
print c
print c.__reduce__()
c[1].append(200)
c[2].append(223)
c2 = pickle.loads(pickle.dumps(c))
c2 == c         
///////////
>From below command, I see 't' should be a tuple:


c.__reduce__()
Out[103]: (__main__.C, (), None, None, <dictionary-itemiterator at 0xaa0dd68>)


Then, I cannot get the idea what the two level parenthesis are for.
Its result is a tuple? Then, it can add 't[2:]'. 

         return (t[0], ()) + t[2:]


It is not a tuple because there is no third level parenthesis, i.e. 

((t[0], ()) + t[2:])


Do you have a simple way for me to make it clear? Thanks,