将python十进制转换为深度嵌套且不可预测的列表中的字符串 [英] Convert python decimal to string in deeply nested and unpredictable list

问题描述

我试图遍历深层嵌套/混合列表中的每个值，并将任何Decimal实例转换为字符串，以便将其存储在mongo中.

I am trying to loop through every value in a deeply nested/mixed list and convert any Decimal instances to string so that I can store them in mongo.

我的递归尝试达到了最大深度.我想以迭代或高性能的方式解决这个问题.

My attempt at recursion reached the max depth. I would like to solve this iteratively or in a performant manner.

这似乎不起作用，但这是我的最新尝试:

This doesn't seem to work but is my latest attempt:

def convert_decimals(root_obj):
    objs_to_convert = [root_obj]

    while objs_to_convert:
        obj = objs_to_convert.pop(0)
        for k, v in enumerate(obj):

            if len(v):
                objs_to_convert.append(v)
            elif isinstance(v, Decimal):
                obj[k] = str(v)

样本输入:

[
    {
        'Payments': {
            'Payment': Decimal('495.64'),
            'IsCapped': True,
            'OtherFees': Decimal('0'),
            'CapCostTotal': Decimal('27900'),
            'Name': 'TestData',
            'Program': {
                'ProgramName': u'AST',
                'Description': None
            },
            'Rate': Decimal('0.0254'),
            'APR': Decimal('2.54'),
            'AppliedIds': [

            ],
            'Tax': Decimal('0')
        }
    }
]

转换后，十进制实例应为字符串

After conversion, the decimal instances should be strings

推荐答案

要在json.dump()期间使用default参数转换Decimal:

To convert Decimal during json.dump() using default parameter:

import json
import sys
from decimal import Decimal

def default(obj):
    if isinstance(obj, Decimal):
        return str(obj)
    else:
        raise TypeError(obj)

# convert during dump
json.dump(data, sys.stdout, indent=2, default=default)

要就地修改data:

import json
import sys
from collections import MutableMapping, MutableSequence
from decimal import Decimal

def convert_decimal(json_data):
    stack = [json_data]
    while stack:
        json_data = stack.pop()
        if isinstance(json_data, MutableMapping): # json object
            it = json_data.items()
        elif isinstance(json_data, MutableSequence): # json array
            it = enumerate(json_data)
        else: # scalar data
            continue

        for k, v in it:
            if isinstance(v, Decimal):
                json_data[k] = str(v)
            else:
                stack.append(v)


# convert inplace
convert_decimal(data)
json.dump(data, sys.stdout, indent=2)

两个脚本产生相同的输出:

Both scripts produce the same output:

[
  {
    "Payments": {
      "OtherFees": "0", 
      "APR": "2.54", 
      "Rate": "0.0254", 
      "IsCapped": true, 
      "Name": "TestData", 
      "Program": {
        "Description": null, 
        "ProgramName": "AST"
      }, 
      "AppliedIds": [], 
      "CapCostTotal": "27900", 
      "Tax": "0", 
      "Payment": "495.64"
    }
  }
]

如果使用通用get_items()函数，则可以简化convert_decimal():

def convert_decimal(json_data):
    stack = [json_data]
    while stack:
        json_data = stack.pop()
        for k, v in get_items(json_data):
            if isinstance(v, Decimal):
                json_data[k] = str(v)
            else:
                stack.append(v)

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