Saving MPRester/MPDataDoc objects

Materials Project Materials Project Data/API
1

Is there a recommended way of saving MPDataDoc objects returned by MPRester offline?

I tried pickling it but that returns an error:
PicklingError: Can't pickle <class 'pydantic.main.MPDataDoc'>: attribute lookup MPDataDoc on pydantic.main failed

pydantic documentation suggests using the model.json() method but that returns:
TypeError: Object of type 'Structure' is not JSON serializable

Is there a convenience function to store a query locally as is.

2

Hi @R_Walser, sorry for the late reply – hope you were able to figure this out. In case this helps anyone else in the future, I prefer to use the saving functionality from the monty package, which we use in pymatgen to serialize/deserialize objects and dump objects to JSON files. For example:

from mp_api.client import MPRester
from monty.serialization import dumpfn, loadfn

with MPRester() as mpr:
    example = mpr.summary.search(material_ids=["mp-49"], fields=["structure", "material_id"])[0]

dumpfn(example, "example_mp_doc.json.gz")

You can then reload this object later by using the corresponding loading function:

example = loadfn("example_mp_doc.json.gz")
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