Python Lambda 函数解析 DynamoDB 的 JSON 格式 [英] Python Lambda Function Parsing DynamoDB's JSON Format

问题描述

为 dynamodb 流调用的 Python Lambda 函数具有 DynamoDB 格式的 JSON(包含 JSON 中的数据类型).我想将 DynamoDB JSON 转换为标准 JSON.PHP 和 nodejs 有 Marshaler 可以做到这一点.如果 Python 有类似或其他选项，请告诉我.

Python Lambda function that gets invoked for a dynamodb stream has JSON that has DynamoDB format (contains the data types in JSON). I would like to covert DynamoDB JSON to standard JSON. PHP and nodejs have Marshaler that can do this. Please let me know if there are similar or other options for Python.

DynamoDB_format = `{"feas":
    {"M": {
        "fea": {
            "L": [
                {
                    "M": {
                        "pre": {
                            "N": "1"
                        },
                        "Li": {
                            "N": "1"
                        },
                        "Fa": {
                            "N": "0"
                        },
                        "Mo": {
                            "N": "1"
                        },
                        "Ti": {
                            "S": "20160618184156529"
                        },
                        "Fr": {
                            "N": "4088682"
                        }
                    }
                }
                ]
            }   
        }
    }
}`

推荐答案

更新:现在有一个库:https://pypi.org/project/dynamodb-json/

这是 indiangolfer 的回答的改进版本.虽然 @indiangolfer 的解决方案适用于该问题，但此改进版本可能对偶然发现此线程的其他人更有用.

Here is an improved version of indiangolfer's answer. While @indiangolfer's solution works for the question, this improved version might be more useful for others who stumble upon this thread.

def unmarshal_dynamodb_json(node):
    data = dict({})
    data['M'] = node
    return _unmarshal_value(data)


def _unmarshal_value(node):
    if type(node) is not dict:
        return node

    for key, value in node.items():
        # S – String - return string
        # N – Number - return int or float (if includes '.')
        # B – Binary - not handled
        # BOOL – Boolean - return Bool
        # NULL – Null - return None
        # M – Map - return a dict
        # L – List - return a list
        # SS – String Set - not handled
        # NN – Number Set - not handled
        # BB – Binary Set - not handled
        key = key.lower()
        if key == 'bool':
            return value
        if key == 'null':
            return None
        if key == 's':
            return value
        if key == 'n':
            if '.' in str(value):
                return float(value)
            return int(value)
        if key in ['m', 'l']:
            if key == 'm':
                data = {}
                for key1, value1 in value.items():
                    if key1.lower() == 'l':
                        data = [_unmarshal_value(n) for n in value1]
                    else:
                        if type(value1) is not dict:
                            return _unmarshal_value(value)
                        data[key1] = _unmarshal_value(value1)
                return data
            data = []
            for item in value:
                data.append(_unmarshal_value(item))
            return data

从以下几个方面进行改进:

It is improved in the following ways:

• 处理更多数据类型，包括以前未正确处理的列表

• handles more data types, including lists, which were not handled correctly previously

处理小写和大写键

修复递归对象错误

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