Python / Django处理错误UNIQUE约束

Question

美好的一天。

我正在编写一个小脚本，该脚本使用Feedparser提取RSS数据。

我将其工作到可以将我需要的所有内容拉到数据库中并将其存储在那里的地方。

现在，为了避免数据重复，我在模型中设置Unique = True。

当然，现在我正在处理错误

return Database.Cursor.execute(self, query, params) sqlite3.IntegrityError: UNIQUE constraint failed: jobrss_rssjob.link

好的，这不是在复制数据。 但是，它完全使脚本崩溃，因此它将停止。

显然，我现在需要为错误编写一个异常-这几乎就是我所困的地方，因为它们也会向我抛出错误。

这是我的代码：

from __future__ import unicode_literals
import feedparser
from django.utils import timezone
import json
from django.db import IntegrityError

from jobrss.models import RSSJob

try:
        def run():

            sources = [
        "https://mybroadband.co.za/vb/external.php?type=RSS2&forumids=269",
        "http://www.bizcommunity.com/rssjobs.aspx?l=196&c=11&s=Developer&sm=1"
            ]
            data = []
            for url in sources:
                data.append(feedparser.parse(url))
                for data in data:
                    for post in data.entries:
                        title = post.title
                        link = post.link
                        add = RSSJob()
                        add.title = title
                        add.link = link
                        add.save()
                        print("Added successfully")
except IntegrityError:
    print("Data Already exists")

有什么建议可以改善这一点吗？

哦，这些是错误。 在空数据库上运行脚本时：

(techvenv) Ronalds-MacBook-Pro:TWNEW burgundy$ python manage.py runscript rsspull
Added successfully
Added successfully
Added successfully
Added successfully
Added successfully
Added successfully
Added successfully
Added successfully
Added successfully
Added successfully
Added successfully
Added successfully
Added successfully
Added successfully
Added successfully
Exception while running run() in 'scripts.rsspull'
Traceback (most recent call last):
  File "/Users/burgundy/dev/Projects/techvenv/lib/python3.6/site-packages/feedparser.py", line 398, in __getattr__
    return self.__getitem__(key)
  File "/Users/burgundy/dev/Projects/techvenv/lib/python3.6/site-packages/feedparser.py", line 356, in __getitem__
    return dict.__getitem__(self, key)
KeyError: 'append'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "manage.py", line 22, in <module>
    execute_from_command_line(sys.argv)
  File "/Users/burgundy/dev/Projects/techvenv/lib/python3.6/site-packages/django/core/management/__init__.py", line 364, in execute_from_command_line
    utility.execute()
  File "/Users/burgundy/dev/Projects/techvenv/lib/python3.6/site-packages/django/core/management/__init__.py", line 356, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/Users/burgundy/dev/Projects/techvenv/lib/python3.6/site-packages/django_extensions/management/email_notifications.py", line 63, in run_from_argv
    super(EmailNotificationCommand, self).run_from_argv(argv)
  File "/Users/burgundy/dev/Projects/techvenv/lib/python3.6/site-packages/django/core/management/base.py", line 283, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/Users/burgundy/dev/Projects/techvenv/lib/python3.6/site-packages/django_extensions/management/email_notifications.py", line 75, in execute
    super(EmailNotificationCommand, self).execute(*args, **options)
  File "/Users/burgundy/dev/Projects/techvenv/lib/python3.6/site-packages/django/core/management/base.py", line 330, in execute
    output = self.handle(*args, **options)
  File "/Users/burgundy/dev/Projects/techvenv/lib/python3.6/site-packages/django_extensions/management/utils.py", line 59, in inner
    ret = func(self, *args, **kwargs)
  File "/Users/burgundy/dev/Projects/techvenv/lib/python3.6/site-packages/django_extensions/management/commands/runscript.py", line 238, in handle
    run_script(mod, *script_args)
  File "/Users/burgundy/dev/Projects/techvenv/lib/python3.6/site-packages/django_extensions/management/commands/runscript.py", line 148, in run_script
    mod.run(*script_args)
  File "/Users/burgundy/dev/Projects/TWNEW/scripts/rsspull.py", line 18, in run
    data.append(feedparser.parse(url))
  File "/Users/burgundy/dev/Projects/techvenv/lib/python3.6/site-packages/feedparser.py", line 400, in __getattr__
    raise AttributeError("object has no attribute '%s'" % key)
AttributeError: object has no attribute 'append

这是当我再次运行它时：

django.db.utils.IntegrityError: UNIQUE constraint failed: jobrss_rssjob.link

亲切的问候。 :)

Answer 1

您的错误是您在定义和运行函数之前捕获了异常。 您需要在run()函数内移动try...except块。

考虑一下：

>>> try:
        def run():
            print(1 / 0)
    except ZeroDivisionError:
        print "Can't divide by zero"

>>> run()
Traceback (most recent call last):
  File "<stdin>", line 3, in <module>
ZeroDivisionError: integer division or modulo by zero

发生这种情况的原因是，当我们定义一个函数时，Python实际上并未运行该函数。 因此， 1 / 0而我们所定义的函数不会引发任何错误。 在这里， try...except块仅会在函数定义期间捕获任何错误。 但是，当我们调用run()函数时，我们正在try...except块之外运行它。 这就是为什么我们得到错误。

---

解决方法：

将try...except块移到run()函数最里面的for循环内。 例：

def run():
    for url in sources:
        data.append(feedparser.parse(url))
        for data in data:
                for post in data.entries:
                    try:
                        title = post.title
                        ...
                        print("Added successfully")
                    except IntegrityError:
                        print("Data Already exists")