名称“Key”未定义用于访问 DynamoDB 的 Lambda 函数

Question

我在 Python 中使用 boto3 库中的查询函数并收到以下错误：

 name 'Key' is not defined: NameError
Traceback (most recent call last):
File "/var/task/lambda_function.py", line 51, in lambda_handler
if not getAssetExistance(slack_userID):
File "/var/task/lambda_function.py", line 23, in getAssetExistance
response = dynamoTable.query(KeyConditionExpression=Key('userID').eq(asset))
NameError: name 'Key' is not defined

我一直在阅读一系列关于通过 Lambda 访问 DynamoDB 的教程，并且他们在尝试是否存在密钥时都使用此 KeyConditionExpression 行。

这是相关代码（第 23 行是查询行）：

 def getAssetExistance(asset):
    dynamoTable = dynamo.Table('Assets')
    response    = dynamoTable.query(KeyConditionExpression=Key('userID').eq(asset))

    return bool(response)

我基本上想检查我的 DynamoDB 表中的主分区键（这是一个松弛的用户 ID）并查看是否存在。

如果相关，这是其余代码：

 ################################
# Slack Lambda handler.
################################

import boto3
import logging
import os
import urllib

# Grab data from the environment.
BOT_TOKEN   = os.environ["BOT_TOKEN"]
ASSET_TABLE = os.environ["ASSET_TABLE"]
REGION_NAME = os.getenv('REGION_NAME', 'us-east-1')

dynamo = boto3.resource('dynamodb', region_name=REGION_NAME, endpoint_url="https://dynamodb.us-east-1.amazonaws.com")

# Define the URL of the targeted Slack API resource.
SLACK_URL = "https://slack.com/api/chat.postMessage"

def getAssetExistance(asset):
    dynamoTable = dynamo.Table('Assets')
    response    = dynamoTable.query(KeyConditionExpression=Key('userID').eq(asset))

    return bool(response)

def lambda_handler(data, context):
    # Slack challenge answer.
    if "challenge" in data:
        return data["challenge"]

    # Grab the Slack channel data.
    slack_event    = data['event']
    slack_userID   = slack_event["user"]
    slack_text     = slack_event["text"]
    channel_id     = slack_event["channel"]
    slack_reply    = ""

    # Ignore bot messages.
    if "bot_id" in slack_event:
        slack_reply = ""
    else:

        # Start data sift.
        if slack_text.startswith("!networth"):
            slack_reply = "Your networth is: "
        elif slack_text.startswith("!price"):
            command,asset = text.split()
            slack_reply = "The price of a(n) %s is: " % (asset)
        elif slack_text.startswith("!addme"):
            if not getAssetExistance(slack_userID):
                slack_reply = "Adding user: %s" % (slack_userID)
                dynamo.update_item(TableName=ASSET_TABLE,
                    Key={'userID':{'S':'slack_userID'}},
                    AttributeUpdates= {
                        'resources':{
                            'Action': 'ADD',
                            'Value': {'N': '1000'}
                        }
                    }
                )
            else:
                slack_reply = "User %s already exists" % (slack_userID)

        # We need to send back three pieces of information:
        data = urllib.parse.urlencode(
            (
                ("token", BOT_TOKEN),
                ("channel", channel_id),
                ("text", slack_reply)
            )
        )
        data = data.encode("ascii")

        # Construct the HTTP request that will be sent to the Slack API.
        request = urllib.request.Request(
            SLACK_URL,
            data=data,
            method="POST"
        )
        # Add a header mentioning that the text is URL-encoded.
        request.add_header(
            "Content-Type",
            "application/x-www-form-urlencoded"
        )

        # Fire off the request!
        urllib.request.urlopen(request).read()

    # Everything went fine.
    return "200 OK"

我的 DynamoDB 表名为“资产”，并且有一个名为“用户 ID”（字符串）的主分区键。

我对这一切绝对还是新手，所以不要害怕称我为傻瓜。任何和所有的帮助表示赞赏。此代码的目标是检查用户是否作为键存在于 DynamoDB 中，如果不存在，则将其添加到表中。

原文由 slnd54 发布，翻译遵循 CC BY-SA 4.0 许可协议

Answer 1

您需要导入 Key 函数，如下所示：

 from boto3.dynamodb.conditions import Key

原文由 Mark B 发布，翻译遵循 CC BY-SA 3.0 许可协议

Answer 2

无需第二次导入，您可以像这样解决它： boto3.dynamodb.conditions.Key

 def getAssetExistance(asset):
dynamoTable = dynamo.Table('Assets')
response    = dynamoTable.query(KeyConditionExpression= boto3.dynamodb.conditions.Key('userID').eq(asset))

return bool(response)

原文由 Saigets 发布，翻译遵循 CC BY-SA 4.0 许可协议