Is there a way to tell pymongo to use a custom encoder to convert python objects to BSON?
Specifically I need to convert numpy arrays into BSON. I know I can manually ensure every numpy array gets converted to a native python array before sending it to pymongo. But this is repetitive and error-prone. I'd much rather have a way to set up my pymongo connection to do this automatically.
You need to write a SONManipulator
. From the docs:
SONManipulator instances allow you to specify transformations to be applied automatically by PyMongo.
from pymongo.son_manipulator import SONManipulator
class Transform(SONManipulator):
def transform_incoming(self, son, collection):
for (key, value) in son.items():
if isinstance(value, Custom):
son[key] = encode_custom(value)
elif isinstance(value, dict): # Make sure we recurse into sub-docs
son[key] = self.transform_incoming(value, collection)
return son
def transform_outgoing(self, son, collection):
for (key, value) in son.items():
if isinstance(value, dict):
if "_type" in value and value["_type"] == "custom":
son[key] = decode_custom(value)
else: # Again, make sure to recurse into sub-docs
son[key] = self.transform_outgoing(value, collection)
return son
then add it to your pymongo database object:
db.add_son_manipulator(Transform())
Note you don't have to add the _type
field if you want to silently cast a numpy array to a python array.
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