How to tackle with error ''Object of type int32 is not JSON serializable''

Question

I am trying to save one dict data in .json file format. When I try json.dump(JSON, json_file), it throws the error: Object of type int32 is not JSON serializable.

I know, it is because I am using some numpy data in dictionary.

Here is the code, that I tried.

import json
for i in range(1):
    g = Balea_coordinate[i] # numpy array
    h = DM_coordinate[i]  # numpy array
    JSON = {"img_metadata" :  {
            "date" : "date",
            "Method" : "SIFT+RANSACK",
            "filename" : "Balea_",
            "size" : "SIZE",
            "regions":[{"0":{"shape_attributes":{"name":"polygon","all_points_x":[g[0,0,0],g[1,0,0],g[2,0,0],g[3,0,0]],
            "all_points_y":[g[0,0,1],g[1,0,1],g[2,0,1],g[3,0,1]]},
            "region_attributes":{"name":"Logo","type":"Balea"}},
            "1":{"shape_attributes":{"name":"polygon","all_points_x":[h[0,0,0],h[1,0,0],h[2,0,0],h[3,0,0]],
            "all_points_y":[h[0,0,1],h[1,0,1],h[2,0,1],h[3,0,1]]},
            "region_attributes":{"name":"Logo","type":"DM"}}}]}}
    with open('personal.json', 'w') as json_file:
        json.dump(JSON, json_file)
´´´

Answer 1

I suggest extending the default JSONEncoder to handle the numpy.int32 type (or any other required type).

class npEncoder(json.JSONEncoder):
    def default(self, obj):
        if isinstance(obj, np.int32):
            return int(obj)
        return json.JSONEncoder.default(self, obj)

Then use it in json.dump(JSON, json_file, cls=npEncoder) . Depending on your requirements, a simple conversion np.int32 -> int might not be sufficient.