python - How to pickle Keras model?

Question

Official documents state that "It is not recommended to use pickle or cPickle to save a Keras model."

However, my need for pickling Keras model stems from hyperparameter optimization using sklearn's RandomizedSearchCV (or any other hyperparameter optimizers). It's essential to save the results to a file, since then the script can be executed remotely in a detached session etc.

Essentially, I want to:

trial_search = RandomizedSearchCV( estimator=keras_model, ... )
pickle.dump( trial_search, open( "trial_search.pickle", "wb" ) )

Answer 1

This works like a charm http://zachmoshe.com/2017/04/03/pickling-keras-models.html:

import types
import tempfile
import keras.models

def make_keras_picklable():
    def __getstate__(self):
        model_str = ""
        with tempfile.NamedTemporaryFile(suffix='.hdf5', delete=True) as fd:
            keras.models.save_model(self, fd.name, overwrite=True)
            model_str = fd.read()
        d = { 'model_str': model_str }
        return d

    def __setstate__(self, state):
        with tempfile.NamedTemporaryFile(suffix='.hdf5', delete=True) as fd:
            fd.write(state['model_str'])
            fd.flush()
            model = keras.models.load_model(fd.name)
        self.__dict__ = model.__dict__


    cls = keras.models.Model
    cls.__getstate__ = __getstate__
    cls.__setstate__ = __setstate__

make_keras_picklable()

PS. I had some problems, due to my model.to_json() raised TypeError('Not JSON Serializable:', obj) due to circular reference, and this error has been swallowed by the code above somehow, hence resulting in pickle function running forever.