Python regex causing list index out of range error

Question

Trying to extract just the email address from this format:

John Smith <[email protected]>

I have tried both of the following and it results in the same error:

IndexError: list index out of range

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

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

Rest of code:

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)

Can anyone please help? I am using Google App Engine with Python if that matters.

can you do print(sender) and add the output to your question? — hansaplast
– hansaplast, Commented Dec 22, 2017 at 22:18
the regex looks good, it gets [email protected] out of "John Smith <[email protected]>" — hansaplast
– hansaplast, Commented Dec 22, 2017 at 22:19
The first regex works for me (assuming sender is John Smith <[email protected]>). The second one works if you add a plus sign after the closing square bracket. — John Gordon
– John Gordon, Commented Dec 22, 2017 at 22:21

Persi · Accepted Answer · 2017-12-22 23:32:43Z

1

In my case first regex works fine:

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

Second is invalid because you get empty list as a result, so you can't get item at index 0:

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

You can check your regex at http://rubular.com/ It's free and easy to use.

edited Dec 22, 2017 at 23:32

answered Dec 22, 2017 at 23:01

Persi

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