如何室壁运动示例脚本解析“未定义的变量”？

Question

我在跟随的Python 3.6.2文档。

100％新Python和从网上抓取的例子来学习我有一个脚本在这里，我试图让工作：

Getting Started with AWS Kinesis and Python

我的PyDev IDE说： “未定义的变量：响应” 的脚本的第10行：

1）作为新的Python的，我canno理解这里使用的语言结构是什么？它看起来像一个多维阵列（从Java背景是未来..）

响应[ 'StreamDescription'] [ '碎片'] [0] [ 'ShardId']

2。 ）如何解决使其不再是“未定义”？

SCRIPT：

import boto3 
import json 
from datetime import datetime 
import time 

my_stream_name = 'python-stream' 

kinesis_client = boto3.client('kinesis', region_name='us-east-1') 

my_shard_id = response['StreamDescription']['Shards'][0]['ShardId'] 

shard_iterator = kinesis_client.get_shard_iterator(StreamName=my_stream_name, 
                 ShardId=my_shard_id, 
                 ShardIteratorType='LATEST') 

my_shard_iterator = shard_iterator['ShardIterator'] 

record_response = kinesis_client.get_records(ShardIterator=my_shard_iterator, 
               Limit=2) 

while 'NextShardIterator' in record_response: 
    record_response = kinesis_client.get_records(ShardIterator=record_response['NextShardIterator'], 
                Limit=2) 

    print record_response 

    # wait for 5 seconds 
    time.sleep(5) 

Answer 1

在你的榜样，你的response变量没有分配任何地方的任何值。根据您的示例response变量保存您的流描述的响应。

我建议蟒蛇REPL上手，

$ python 
Python 2.7.13 (default, Apr 4 2017, 08:46:44) 
[GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.42.1)] on darwin 
Type "help", "copyright", "credits" or "license" for more information. 
>>> import boto3 
>>> import json 

>>> boto3.setup_default_session(profile_name="aws-federated") //using credentials localted in ~/.aws/credentials 
>>> client = boto3.client('kinesis', region_name='us-west-2') //I use west regiion, you can change to east as in your question 

我有一个名为gregor-samsa-2流，

>>> client.list_streams(Limit=100) 
{u'StreamNames': [u'gregor-samsa-1', u'gregor-samsa-2', u'HasMoreStreams': False, 'ResponseMetadata': {'RetryAttempts': 0, 'HTTPStatusCode': 200, 'RequestId': 'ed632ba9-8bba-3173-bc93-5b04547d1f2a', 'HTTPHeaders': {'x-amzn-requestid': 'ed632ba9-8bba-3173-bc93-5b04547d1f2a', 'content-length': '244', 'x-amz-id-2': 'NJpwLfREWneUwQHIYrS+L9EmUwTUyywMLUWNzNK53C1GIKRZx8/z2TiMe9+oY3eOblNxYleMkEHPCP7D7An3Clw4EII+Tn5M', 'server': 'Apache-Coyote/1.1', 'date': 'Mon, 24 Jul 2017 22:02:20 GMT', 'content-type': 'application/x-amz-json-1.1'}}} 

>>> response = client.describe_stream(StreamName='gregor-samsa-2') 

如果打印响应，其一个HashMap /或Python的条款及其Dictionary。

>>> response 
{'ResponseMetadata': {'RetryAttempts': 0, 'HTTPStatusCode': 200, 'RequestId': 'f4130cb3-6ffb-aebe-a5e3-7e831eeea949', 'HTTPHeaders': {'x-amzn-requestid': 'f4130cb3-6ffb-aebe-a5e3-7e831eeea949', 'content-length': '841', 'x-amz-id-2': 'O0qfcRJcv9NrNlPc+DmjMPl4Fa9LKl/3D4dxzD+BQTnkisAlL3chw8P5GGZFcUSmHi+WaDBSWcNvcGuHQcfivJN2EBN7nPig', 'server': 'Apache-Coyote/1.1', 'date': 'Mon, 24 Jul 2017 22:08:47 GMT', 'content-type': 'application/x-amz-json-1.1'}}, u'StreamDescription': {u'HasMoreShards': False, u'RetentionPeriodHours': 24, u'StreamName': u'gregor-samsa-2', u'Shards': [{u'ShardId': u'shardId-000000000000', u'HashKeyRange': {u'EndingHashKey': u'170141183460469231731687303715884105727', u'StartingHashKey': u'0'}, u'SequenceNumberRange': {u'StartingSequenceNumber': u'49574403640320687182855826859993394354817752107006820354'}}, {u'ShardId': u'shardId-000000000001', u'HashKeyRange': {u'EndingHashKey': u'340282366920938463463374607431768211455', u'StartingHashKey': u'170141183460469231731687303715884105728'}, u'SequenceNumberRange': {u'StartingSequenceNumber': u'49574403640342987928054357483134930073090400468512800786'}}], u'StreamARN': u'arn:aws:kinesis:us-west-2:033814027302:stream/gregor-samsa-2', u'EnhancedMonitoring': [{u'ShardLevelMetrics': []}], u'StreamCreationTimestamp': datetime.datetime(2017, 6, 22, 0, 51, 53, tzinfo=tzlocal()), u'StreamStatus': u'ACTIVE'}} 

>>> print(type(response)) 
<type 'dict'> 

为了得到你想要查询的分区，访问响应的HashMap，你在做你的榜样，（使用dictionary['key1']['key2']）

response['StreamDescription']['Shards']给出了一个阵列。

>>> print(type(response['StreamDescription']['Shards'])) 
<type 'list'> 

您可以使用list[index]模式访问列表。

>>> response['StreamDescription']['Shards'][0]['ShardId'] 
u'shardId-000000000000' 

退出蟒蛇REPL，

>>> exit()