How to check for valid email address? [duplicate]

Answer 1

If you want to take out the mail from a long string or file Then try this.

([^@|\s]+@[^@]+\.[^@|\s]+)

Note, this will work when you have a space before and after your email-address. if you don't have space or have some special chars then you may try modifying it.

Working example:

string="Hello ABCD, here is my mail id example@me.com "
res = re.search("([^@|\s]+@[^@]+\.[^@|\s]+)",string,re.I)
res.group(1)

This will take out example@me.com from this string.

Also, note this may not be the right answer... But I have posted it here to help someone who has specific requirement like me

Answer 2

Found this to be a practical implementation:

[^@\s]+@[^@\s]+\.[^@\s]+

Answer 3

Email addresses are incredibly complicated. Here's a sample regex that will match every RFC822-valid address: http://www.ex-parrot.com/pdw/Mail-RFC822-Address.html

You'll notice that it's probably longer than the rest of your program. There are even whole modules for Perl with the purpose of validating email addresses. So you probably won't get anything that's 100% perfect as a regex while also being readable. Here's a sample recursive descent parser: http://cpansearch.perl.org/src/ABIGAIL/RFC-RFC822-Address-2009110702/lib/RFC/RFC822/Address.pm

but you'll need to decide whether you need perfect parsing or simple code.

Answer 4

I see a lot of complicated answers here. Some of them, fail to knowledge simple, true email address, or have false positives. Below, is the simplest way of testing that the string would be a valid email. It tests against 2 and 3 letter TLD's. Now that you technically can have larger ones, you may wish to increase the 3 to 4, 5 or even 10.

import re
def valid_email(email):
  return bool(re.search(r"^[\w\.\+\-]+\@[\w]+\.[a-z]{2,3}$", email))

Answer 5

I haven't seen the answer already here among the mess of custom Regex answers, but...

There exists a python library called py3-validate-email validate_email which has 3 levels of email validation, including asking a valid SMTP server if the email address is valid (without sending an email).

To install

python -m pip install py3-validate-email

Basic usage:

from validate_email import validate_email
is_valid = validate_email(email_address='example@example.com', \
    check_regex=True, check_mx=True, \
    from_address='my@from.addr.ess', helo_host='my.host.name', \ 
    smtp_timeout=10, dns_timeout=10, use_blacklist=True)

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For those interested in the dirty details, validate_email.py (source) aims to be faithful to RFC 2822.

All we are really doing is comparing the input string to one gigantic regular expression. But building that regexp, and ensuring its correctness, is made much easier by assembling it from the "tokens" defined by the RFC. Each of these tokens is tested in the accompanying unit test file.

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you may need the pyDNS module for checking SMTP servers

pip install pyDNS

or from Ubuntu

apt-get install python3-dns

Answer 6

There is no point. Even if you can verify that the email address is syntactically valid, you'll still need to check that it was not mistyped, and that it actually goes to the person you think it does. The only way to do that is to send them an email and have them click a link to verify.

Therefore, a most basic check (e.g. that they didn't accidentally entered their street address) is usually enough. Something like: it has exactly one @ sign, and at least one . in the part after the @:

[^@]+@[^@]+\.[^@]+

You'd probably also want to disallow whitespace -- there are probably valid email addresses with whitespace in them, but I've never seen one, so the odds of this being a user error are on your side.

If you want the full check, have a look at this question.

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Update: Here's how you could use any such regex:

import re

if not re.match(r"... regex here ...", email):
  # whatever

Python ≥3.4 has re.fullmatch which is preferable to re.match.

Note the r in front of the string; this way, you won't need to escape things twice.

If you have a large number of regexes to check, it might be faster to compile the regex first:

import re

EMAIL_REGEX = re.compile(r"... regex here ...")

if not EMAIL_REGEX.match(email):
  # whatever

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Another option is to use the validate_email package, which actually contacts the SMTP server to verify that the address exists. This still doesn't guarantee that it belongs to the right person, though.