循环 10 小时后出现 KeyError

Question

在以下脚本循环 15 秒后，我在以下脚本中收到以下 KeyError，完美运行了 10 个小时左右。为什么每 15 秒运行一次关键错误，却在 10 小时内只出现一次？

错误：

Traceback (most recent call last):

  File "C:\venderFix.py", line 33, in <module>

    if j['results']:

KeyError: 'results'

代码：

import json
import urllib
from pprint import pprint
import time
from arduino import Arduino

vendtime = 0.2                                           
delayTime = 15                                               
searchTerm = 'happy'                      

A = Arduino('COM3') #This will need to be COM3               
A.output([12]) #Output on pin 12                             

countTweet = 0
#To test Twitter for consistancy 
tweet= 0
noTweet= 0



#the infinate loop
while True:

    #j contains the JSON we load from the URL
    j =json.loads(urllib.urlopen('http://search.twitter.com/search.json?q='+searchTerm+'&result_type=recent&rpp=1&filter:retweets').read())

    #Debug JSON from twitter (for faults on the Twitter end or possible GET limit id below 15 seconds per request)
    #pprint(j) #needed for debugging only

    #find the text and the tweet id
    if j['results']:
        text = j['results'][0]['text']
        id = j['results'][0]['id']
        #how many times the Json is complete
        tweet+= 1
    else:
        #How many times the Json is incomplete (sometimes twitter malfunctions. About 0.1 in 100 are broken)
        noTweet += 1

    #print the text and id to the screen
    pprint(text) #needed for debugging only
    pprint(id)   #needed for debugging only

    #to get the existing tweet from before we power on, if the first ID has been stored already (count == 1)
    if countTweet != 0:  #if countTweet is not equal to 0 then it's not the first tweet
        #pprint ("new loop") #needed for debugging only

        #if lastID is not equal to ID
        if lastID != id:
        #Tell Arduino to Vend
            #pin 12 HIGH
            A.setHigh(12)
            #Sleep for the time specified in vendtime
            time.sleep(vendtime)
            #pin 12 LOW
            A.setLow(12)
            #Display the tweet that triggered the vend
            #pprint(text) #needed for debugging only
            #pprint(id)   #needed for debugging only
            #Make lastID equal to ID so that next time we can compare it 
            lastID = id
            #pprint ('lastID updated') #needed for debugging only
        #if no new tweets, print     
        else:  #needed for debugging only
            pprint ('no new tweets') #needed for debugging only
    #If it's the first loop, confirm by printing to the screen
    else:
        pprint("First loop complete")
        pprint(text)
        pprint(id)
        lastID = id
        pprint(lastID)
        countTweet += 1 #Add 1 to countTweet

    pprint ('Number of Tweets')
    pprint (countTweet)
    pprint('Working JSON')
    pprint(tweet)
    pprint('Broken JSON')
    pprint(noTweet)

    pprint('waiting')
    time.sleep(delayTime)

Answer 1

只是因为在那次迭代中，您的 dict 中没有密钥 results。

测试一个键是否在字典中的正确方法是：

if 'result' in j:
     .... 

如果您还想检查它的值是否不是None 或任何其他虚假值，那么：

if 'result' in j and j['result']:
    ...

另一个与您正在调用服务的事实相关的假设是，服务器不时会返回一条错误消息。

如果发生这种情况，JSON 结构可能不是您所期望的，您应该检查文档是否对此有任何说明并进行相应处理。