Here is my final solution that was adapted from hpaulj’s answer, and his answer to this thread: https://stackoverflow.com/a/24375113/901925
This will encode/decode arrays that are nested to arbitrary depth in nested dictionaries, of any datatype.
import base64
import json
import numpy as np
class NumpyEncoder(json.JSONEncoder):
def default(self, obj):
"""
if input object is a ndarray it will be converted into a dict holding dtype, shape and the data base64 encoded
"""
if isinstance(obj, np.ndarray):
data_b64 = base64.b64encode(obj.data)
return dict(__ndarray__=data_b64,
dtype=str(obj.dtype),
shape=obj.shape)
# Let the base class default method raise the TypeError
return json.JSONEncoder(self, obj)
def json_numpy_obj_hook(dct):
"""
Decodes a previously encoded numpy ndarray
with proper shape and dtype
:param dct: (dict) json encoded ndarray
:return: (ndarray) if input was an encoded ndarray
"""
if isinstance(dct, dict) and '__ndarray__' in dct:
data = base64.b64decode(dct['__ndarray__'])
return np.frombuffer(data, dct['dtype']).reshape(dct['shape'])
return dct
# Overload dump/load to default use this behavior.
def dumps(*args, **kwargs):
kwargs.setdefault('cls', NumpyEncoder)
return json.dumps(*args, **kwargs)
def loads(*args, **kwargs):
kwargs.setdefault('object_hook', json_numpy_obj_hook)
return json.loads(*args, **kwargs)
def dump(*args, **kwargs):
kwargs.setdefault('cls', NumpyEncoder)
return json.dump(*args, **kwargs)
def load(*args, **kwargs):
kwargs.setdefault('object_hook', json_numpy_obj_hook)
return json.load(*args, **kwargs)
if __name__ == '__main__':
data = np.arange(3, dtype=np.complex)
one_level = {'level1': data, 'foo':'bar'}
two_level = {'level2': one_level}
dumped = dumps(two_level)
result = loads(dumped)
print '\noriginal data', data
print '\nnested dict of dict complex array', two_level
print '\ndecoded nested data', result
Which yields output:
original data [ 0.+0.j 1.+0.j 2.+0.j]
nested dict of dict complex array {'level2': {'level1': array([ 0.+0.j, 1.+0.j, 2.+0.j]), 'foo': 'bar'}}
decoded nested data {u'level2': {u'level1': array([ 0.+0.j, 1.+0.j, 2.+0.j]), u'foo': u'bar'}}