编辑：
convert_decimal()函数将在复杂的dict结构中执行Decimal到Decimal128的转换：

import simplejson as json
from pymongo import MongoClient
from decimal import Decimal
from bson.decimal128 import Decimal128

def convert_decimal(dict_item):
    # This function iterates a dictionary looking for types of Decimal and converts them to Decimal128
    # Embedded dictionaries and lists are called recursively.
    if dict_item is None: return None

    for k, v in list(dict_item.items()):
        if isinstance(v, dict):
            convert_decimal(v)
        elif isinstance(v, list):
            for l in v:
                convert_decimal(l)
        elif isinstance(v, Decimal):
            dict_item[k] = Decimal128(str(v))

    return dict_item

db = MongoClient()['mydatabase']
json_string = '{"A" : {"B" : [{"C" : {"Horz" : 0.181665435,"Vert" : 0.178799435}}]}}'
json_dict = json.loads(json_string, use_decimal=True)
db.this_collection.insert_one(convert_decimal(json_dict))
print(db.this_collection.find_one())

给出：

{'_id': ObjectId('5ea743aa297c9ccd52d33e05'), 'A': {'B': [{'C': {'Horz': Decimal128('0.181665435'), 'Vert': Decimal128('0.178799435')}}]}}

原件：
要将一个十进制转换为MongoDB满意的Decimal128，先将其转换为字符串，然后再转换为Decimal128。

from pymongo import MongoClient
from decimal import Decimal
from bson.decimal128 import Decimal128

db = MongoClient()['mydatabase']
your_number = Decimal('234.56')
your_number_128 = Decimal128(str(your_number))
db.mycollection.insert_one({'Number': your_number_128})
print(db.mycollection.find_one())

给出：

{'_id': ObjectId('5ea6ec9b52619c7b39b851cb'), 'Number': Decimal128('234.56')}

Pymongo不能识别Decimal-这就是为什么你会得到错误。
正确的pymongo插入是coll.insert_one({"number1": Decimal128('8.916')})。
您还需要导入-from bson import Decimal128
现在，如果希望在不将Decimal更改为Decimal 128 '的情况下处理JSON文件，可以修改import语句。

from bson import Decimal128 as Decimal

coll.insert_one({"number1": Decimal('8.916')})

from bson.decimal128 import Decimal128, create_decimal128_context
from decimal import localcontext

decimal128_ctx = create_decimal128_context()
with localcontext(decimal128_ctx) as ctx:
    horiz_val = Decimal128(ctx.create_decimal("0.181665435"))
    vert_val = Decimal128(ctx.create_decimal("0.178799435"))

doc = { 'A': { 'B': [ { 'C': { 'Horiz': horiz_val, 'Vert': vert_val } } ] } }
result = collection.insert_one(doc)
# result.inserted_id

pprint.pprint(list(collection.find()))

[ {'A': {'B': [{'C': {'Horiz': Decimal128('0.181665435'),
                      'Vert': Decimal128('0.178799435')}}]},
  '_id': ObjectId('5ea79adb915cbf3c46f5d4ae')} ]

注：

• 皮蒙戈的decimal128 - Support for BSON Decimal128
• Python的decimal模块支持十进制浮点运算。

从PyMongo的decimal128文档中：
为确保计算结果始终存储为BSON Decimal128，请使用create_decimal128_context()返回的上下文（注：如上面的示例代码所示）。

我建议只添加一个编解码器来在插入时自动转换数据类型。如果你递归地改变数据类型来使用Decimal128对象，你可能会破坏与现有代码的兼容性。
您可以按照教程创建一个简单的decimal.Decimal编解码器，请参阅pymongo docs here

已接受的答案here部分正确，但未通过我们使用pytest编写的测试，示例数据如下：

example = {
    "string_field": "some",
    "string_array_list": ["samatta"],
    "decimal_containing_list": ["a", Decimal(8)],
    "empty_list": [],
    "empty_dict": {},
    "direct_decimal": Decimal(0),
    "nested_decimal_dict": {"very_important-field": Decimal(1)},
    "number_field": 1,
    "nested_number_field": {"very_important-field": 1},
    "number_list": [1, 2],
    "decimal_containing_field_list": [{"very_important": Decimal(1)}],
}

这里嵌套数组是这样的。我稍微改进了一下，现在的一个通过了测试：

from typing import Union
    
def convert_decimal(item: Union[dict, list]) -> Union[dict, list]:
    if item is None:
        return None

    elif isinstance(item, list):
        for index, item in enumerate(item):
            if isinstance(item, Decimal):
                item[index] = Decimal128(str(item))
            if isinstance(item, dict):
                convert_decimal(item)
        return item

    elif isinstance(item, dict):
        for k, v in list(item.items()):
            if isinstance(v, dict):
                convert_decimal(v)
            elif isinstance(v, list):
                convert_decimal(v)
            elif isinstance(v, Decimal):
                item[k] = Decimal128(str(v))

        return item

当你把它打印出来的时候

{
    "string_field": "some",
    "string_array_list": ["samatta"],
    "decimal_containing_list": ["a", Decimal128("8")],
    "empty_list": [],
    "empty_dict": {},
    "direct_decimal": Decimal128("0"),
    "nested_decimal_dict": {"very_important-field": Decimal128("1")},
    "number_field": 1,
    "nested_number_field": {"very_important-field": 1},
    "number_list": [1, 2],
    "decimal_containing_field_list": [{"very_important": Decimal128("1")}],
}