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JSON，该JSON具有DynamoDB格式(包含JSON中的数据类型).我想将DynamoDB JSON转换为标准JSON. PHP和nodejs具有Marshaler可以做到这一点.请让我知道Python是否有类似或其他选项.

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/

Update: There is a library now: https://pypi.org/project/dynamodb-json/

这是 indiangolfer的答案的改进版本. 尽管indiangolfer的解决方案可解决该问题，但此改进版本对于偶然发现此线程的其他人可能更有用.

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

它在以下方面得到了改进:

It is improved in the following ways:

• 处理更多的数据类型，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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