--- Scott Gilbert <xscottg@yahoo.com> wrote:
> Have your __reduce__ method return a 4-tuple (function, arguments, state,
> listitems) with:
>
> function = a constructing function that takes the length of your array in
> bytes, and the type of the data in the array
>
> arguments = a 2-tuple specifying the bytes and type
>
> state = None
>
> listitems = an iterator that returns small chunks of memory at a time.
Hey, this is great! I am beginning to see the light.
> I've been gone for a while, is this PEP going to be included in the final
> version of 2.3?
My little prototype below works with Python 2.3a2!
This is almost perfect. In C++ we can have two overloads.
Highly simplified:
template <typename T>
class array<T> {
void append(T const& value); // the regular append
void append(std::string const& value); // for unpickling
};
This will work for all T (e.g. int, float, etc.)
... except T == std::string.
This leads me to find it unfortunate that append() is re-used for
unpickling. How about:
If the object has a (say) __unpickle_append__ method this is used by
the unpickler instead of append or extend.
Ralf
import pickle
class int_array(object):
def __init__(self, elems):
self.elems = list(elems)
def __reduce__(self):
return (int_array_factory,
(len(self.elems),),
None,
int_array_iter(self.elems))
def append(self, value):
values = [int(x) for x in value.split(",")]
self.elems.extend(values)
class int_array_iter(object):
def __init__(self, elems, buf_size=4):
self.elems = elems
self.buf_size = 4
self.i = 0
def __iter__(self):
return self
def next(self):
if (self.i >= len(self.elems)): raise StopIteration
result = ""
for i in xrange(self.buf_size):
result+= str(self.elems[self.i]) + ","
self.i += 1
if (self.i == len(self.elems)): break
return result[:-1]
def int_array_factory(size):
print "reserve:", size
return int_array([])
f = int_array(range(11))
print "f.elems:", f.elems
s = pickle.dumps(f)
print s
g = pickle.loads(s)
print "g.elems:", g.elems
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