[Numpy-discussion] cPickle.loads and Numeric

[Raul Cota]

Robert is right, you can always implement your own function.

What version of numpy and Python are you using ?

There may be something you can add to your numpy installation related to 
the old Numeric support which I believe is now deprecated.

Raul




On 25/02/2014 4:28 AM, Robert Kern wrote:
> On Tue, Feb 25, 2014 at 8:19 AM, Chris <chris.madan at gmail.com> wrote:
>> I have some old code that uses cPickle.loads which used to work, but now
>> reports an error in loading the module Numeric. Since Numeric has been
>> replaced by numpy, this makes sense, but, how can I get cPickle.loads to
>> work? I tested the code again on an older machine and it works fine
>> there, but, I'd like to get it working again on a modern set-up as well.
> It's relatively straightforward to subclass Unpickler to redirect it
> when it goes to look for the array constructor that it expects from
> the Numeric module.
>
>
> from cStringIO import StringIO
> import pickle
>
> import numpy as np
>
>
> TEST_NUMERIC_PICKLE = ('\x80\x02cNumeric\narray_constructor\nq\x01(K\x05\x85U'
>                         '\x01lU(\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00'
>                         '\x00\x00\x00\x00\x02\x00\x00\x00\x00\x00\x00\x00\x03'
>                         '\x00\x00\x00\x00\x00\x00\x00\x04\x00\x00\x00\x00\x00'
>                         '\x00\x00K\x01tRq\x02.')
>
>
> # Constant from Numeric.
> LittleEndian = 1
>
> def array_constructor(shape, typecode, thestr, Endian=LittleEndian):
>      """ The old Numeric array constructor for pickle, recast for numpy.
>      """
>      if typecode == "O":
>          x = np.array(thestr, "O")
>      else:
>          x = np.fromstring(thestr, typecode)
>      x.shape = shape
>      if LittleEndian != Endian:
>          return x.byteswapped()
>      else:
>          return x
>
>
> class NumericUnpickler(pickle.Unpickler):
>      """ Allow loading of pickles containing Numeric arrays and
>      converting them to numpy arrays.
>      """
>
>      def find_class(self, module, name):
>          """ Return the constructor callable for a given "class".
>
>          Overridden to handle Numeric.array_constructor specially.
>          """
>          if module == 'Numeric' and name == 'array_constructor':
>              return array_constructor
>          else:
>              return pickle.Unpickler.find_class(self, module, name)
>
>
> def load(fp):
>      return NumericUnpickler(fp).load()
>
>
> def loads(pickle_string):
>      fp = StringIO(pickle_string)
>      return NumericUnpickler(fp).load()
>
>
> if __name__ == '__main__':
>      import sys
>      print loads(TEST_NUMERIC_PICKLE)
>      # Look, Ma! No Numeric!
>      assert 'Numeric' not in sys.modules
>