Python class: 数据不知何故丢失

Question

我正在尝试定义一个 Python class，它通过 praw 包分析 subreddit 数据。

我对 C++ 中的 OOP 相当有经验，但对 Python 中的 OOP 经验不多。这是我到目前为止的代码：

import praw
class SubRedditAnalyzer:

    def __init__(self, reddit_session, name='dataisbeautiful'):
        self.name = name # subreddit name
        self.reddit_session = reddit_session # assign the reddit session
        self.subreddit = self.reddit_session.get_subreddit(self.name) # create the subreddit object
        self.timeframe = 'day'
        self.max_post_count = 10
        self.submissions = self.subreddit.get_top_from_hour(limit=10)

    def __del__(self):
        class_name = self.__class__.__name__
        print class_name, "destroyed"

    def get_top_submissions(self, max_post_count):

        timeframe = self.timeframe

        if (timeframe == 'hour'):
            self.submissions = self.subreddit.get_top_from_hour(limit= max_post_count)
        elif (timeframe == 'day'):
            self.submissions = self.subreddit.get_top_from_day(limit= max_post_count)
        elif (timeframe == 'week'):
            self.submissions = self.subreddit.get_top_from_week(limit= max_post_count)
        elif (timeframe == 'month'):
            self.submissions = self.subreddit.get_top_from_month(limit= max_post_count)
        elif (timeframe == 'year'):
            self.submissions = self.subreddit.get_top_from_year(limit= max_post_count)
        elif (timeframe == 'all'):
            self.submissions = self.subreddit.get_top_from_all(limit= max_post_count)

    def combine_titles(self):
        titles = ""
        for submission in self.submissions:
            titles += submission.title
        self.titles = titles 

    def display_titles(self):
        counter = 1
        ya = self.submissions
        for sub in self.submissions:
            sc = sub.score
            ti = sub.title
            print('T%d- [%d] %s \n' %(counter,sc,ti))
            counter += 1

def main():
   r = praw.Reddit('Request to fetch data by user')
   sr = SubRedditAnalyzer(r, 'dataisbeautiful')
   sr.get_top_submissions(15) # top 15 from reddit
   sr.combine_titles()        # combine the top titles    
   sr.display_titles()        # display all the titles 

main()

由于某些（对我而言）未知的原因，class 'sr' 中的数据似乎在调用

后丢失了

sr.combine_titles()

当我尝试调用此方法时，class 中的数据为空：

sr.display_titles()

事实上，我确实看到 class 被销毁的消息：

SubRedditAnalyzer 已销毁

我做错了什么？预先感谢您的关注。

Answer 1

似乎 self.submissions 可能是可迭代的但不是集合（例如列表）。 The docs call get_top_from_hour() a generator method (although they state also that what is returned is a list...). If it is indeed a generator method，结果只能迭代一次。所有其他迭代尝试都将无声地失败（display_titles() 中的循环不执行任何操作）。

所以，解决方案是：

self.submissions = list(self.subreddit.get_top_from_hour(limit=10))

在 __init__() 中将可迭代对象转换为可迭代多次的永久集合（列表）。

Answer 2

根据 PRAW 文档，get_content 及其相关方法如 get_top_from_hour return a generator。生成器只能迭代一次，您在 combine_titles 中进行了迭代。该次迭代后，生成器耗尽，无法再次迭代。

当您在 __init__:

中获取提交时，您大概可以将它们转换为列表

self.submissions = list(self.subreddit.get_top_from_hour(limit=10))

Python class: 数据不知何故丢失

Python class: The data is somehow lost

python

oop

class

praw