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This function simply validates an e-mail address. Ignore this recepie and go to my "StringValidator" recepie, which is a much better solution

Python, 8 lines
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import re

def validateEmail(email):

	if len(email) > 7:
		if re.match("^.+\\@(\\[?)[a-zA-Z0-9\\-\\.]+\\.([a-zA-Z]{2,3}|[0-9]{1,3})(\\]?)$", email) != None:
			return 1
	return 0

E-mail address validation is a pretty common thing when dealing with web forms. The reason I check if the length of "email" is greater than 7 is because to the best of my knowledge, no address can be shorter than 7 characters (ie. j@jj.ca).

See my "StringValidator" recepie for a much better solution!

11 comments

nicolas 20 years, 3 months ago  # | flag

Short email adresses. It is important to note that email adresses _can_ be shorter than 7 characters. Although domain names shorter than 2 letters are not allowed in .com .net and .org, many ISO country domain registrars do allow one letter domain names. For example in Denmark, where I live. For example see http://www.n.dk

Stephen White 18 years, 8 months ago  # | flag

Short email addresses and .va. If you'll do 'nslookup -type=mx va' or similar you'll find that va has mail exchangers associated. This means that the shortest email address, IMHO, is .

Peter Sanchez 17 years, 2 months ago  # | flag

.info? Doesn't look like your code will validate .info domains. Here is the regexp I use for my email validation:

re.compile('^[_.0-9a-z-]+@([0-9a-z][0-9a-z-]+.)+[a-z]{2,4}$')

Shekhar Tiwatne 16 years, 2 months ago  # | flag

idn emails. I think this recepie may not validate idn email ids. Try validating user@zääz.de .

Rodolfo Puig 13 years, 8 months ago  # | flag

Production Code. I've been using this regular expression for many years in various production environments (affiliate systems, forums, etc) and it hasn't given me any false positives. Enjoy...

re.match("^[a-zA-Z0-9._%-]+@[a-zA-Z0-9._%-]+.[a-zA-Z]{2,6}$", email_str)

Timothee Besset 13 years, 2 months ago  # | flag

that one in #5 will not accept john+doe@ and john-doe@

I've modified it into:

"^[a-zA-Z0-9._%-+]+@[a-zA-Z0-9._%-]+.[a-zA-Z]{2,6}$"

andreas.mock 13 years ago  # | flag

Hi all,

just came across this recipe and read #5. Here is your false positive:

haha.hoho.@somedomain.de">class="prettyprint">haha.hoho.@somedomain.de

is not a valid e-mail address. But the regex gives no false. Dots at the start and at the end of the local part are not allowed. See RFC2822.

Best regards

Andreas Mock

andrew cooke 10 years, 10 months ago  # | flag

There's an RFC that describes how to validate emails (RFC 3696). I wrote a Python library that implements that. It's part of Lepl. The documentation is here:

http://www.acooke.org/lepl/
http://www.acooke.org/lepl/rfc3696.html

That includes support for IPv6 addresses, for example. The tests at http://www.acooke.org/lepl/api/lepl.apps._test.rfc3696-pysrc.html include many examples that are perfectly valid, but that would be missed by the routines here:

customer/department=shipping@example.com">class="prettyprint">customer/department=shipping@example.com (this one f--ks up the formatting here :o)
!def!xyz%abc@example.com
Abc\@def@example.com
andrew cooke 10 years, 10 months ago  # | flag

Sorry, I should probably include an example.

To install:

easy_install lepl

To use:

from lepl.apps.rfc3696 import Email

assert Email('andrew@acooke.org')
assert not Email('not an email at all!')
Shah, Sandip P. 9 years, 7 months ago  # | flag

The above example did not work for me. This is what worked for me

from lepl.apps.rfc3696 import Email

t1 = Email()

Email function does not take an argument, it is just a validator

if t1('valid_email_address@domain.com'): do something

Shah, Sandip P. 9 years, 7 months ago  # | flag

Dang ... I did not know that a hash sign highlights the comments here .. sorry for that.

Created by Mark Nenadov on Fri, 15 Jun 2001 (PSF)
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