Python正则表达式导致列表索引超出范围错误

Question

尝试从以下格式中提取电子邮件地址：

John Smith <jsmith@email.com>

我已经尝试了以下两种情况并导致同样的错误：

IndexError: list index out of range

email_address = re.findall('(?<=\<)\w+@[a-zA-Z]+\.[a-z]+(?=\>)', sender)[0]

email_address = re.findall('<([^>])>', sender)[0]

其余代码：

import webapp2
import logging
from google.appengine.ext.webapp import mail_handlers
from google.appengine.api import mail
import os
from main import WorkRequest
import re


class IncomingMailHandler(mail_handlers.InboundMailHandler):
    def receive(self, message):
        (encoding, payload) = list(message.bodies(content_type='text/plain'))[0]
        body_text = payload.decode()
        logging.info('Received email message from %s, subject "%s": %s' %
                     (message.sender, message.subject, body_text))

        logging.info (message.sender)
        logging.info(message.subject)
        logging.info(body_text)


        sender = str(message.sender)

        email_address = re.findall('<([^>])>', sender)[0]

        wr = WorkRequest()

        wr.email = email_address
        wr.userId = None
        wr.title = message.subject
        wr.content = body_text
        wr.status = "OPEN"
        wr.submission_type = "EMAIL"
        wr.assigned_to = "UNASSIGNED"
        wr.put()

application = webapp2.WSGIApplication([('/_ah/mail/.+', IncomingMailHandler)],debug=True)

有人可以帮忙吗？如果重要的话，我正在使用带有Python的Google App Engine。

Answer 1

在我的情况下，第一个正则表达式工作正常：

>>> sender = 'John Smith <jsmith@email.com>'
>>> email_address = re.findall('(?<=\<)\w+@[a-zA-Z]+\.[a-z]+(?=\>)', 
        sender)[0]
>>> email_address
'jsmith@email.com'

第二个是无效的，因为你得到一个空列表，所以你不能在索引0获得项目：

email_address = re.findall('<([^>])>', sender)
>>> email_address
[]

您可以在http://rubular.com/查看正则表达式 它免费且易于使用。