记录：TypeError: Object of type int32 is not JSON serializable。

    rect_list = list()

    ...
    rect_list.append(rect1)
    rect_list.append(rect2)
    ...

    rsp = {'rect-list': rect_list}
    return json.dumps(rsp) 

报错

  File "C:UsersmoAppDataLocalProgramsPythonPython39libjsonencoder.py", line 257, in iterencode
    return _iterencode(o, 0)
  File "C:UsersmoAppDataLocalProgramsPythonPython39libjsonencoder.py", line 179, in default
    raise TypeError(f'Object of type {o.__class__.__name__} '
TypeError: Object of type int32 is not JSON serializable

原因

字典格式化为JSON不支持numpy.int32。np.float32、np.array等存在类似问题。

解决（两种 方法原理相同）

• 转Json前，将np类型强制转换为python类型

def cv_rect_to_dict(cv_rect):
    x, y, w, h = cv_rect
    return {'x': int(x), 'y': int(y), 'w': int(w), 'h': int(h)}

• 继承实现自定义Json Encoder

class ZJsonEncoder(json.JSONEncoder):
    def default(self, obj):
        if isinstance(obj, numpy.integer):
            return int(obj)
        elif isinstance(obj, numpy.floating):
            return float(obj)
        elif isinstance(obj, numpy.ndarray):
            return obj.tolist()
        else:
            return super(ZJsonEncoder, self).default(obj)


用法：
    rsp = {'rect-list': rect_list}
    return json.dumps(rsp, cls=ZJsonEncoder)