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Checking validity of email in django/python

Posted by: admin November 30, 2017 Leave a comment

Questions:

I have written a function for adding emails to newsletter base. Until I’ve added checking validity of sent email it was working flawlessly. Now each time I’m getting “Wrong email” in return. Can anybody see any errors here ? The regex used is :

\b[\w\.-][email protected][\w\.-]+\.\w{2,4}\b and it is 100% valid (http://gskinner.com/RegExr/), but I may be using it wrong, or it may be some logic error :

def newsletter_add(request):
    if request.method == "POST":   
        try:
            e = NewsletterEmails.objects.get(email = request.POST['email'])
            message = _(u"Email is already added.")
            type = "error"
        except NewsletterEmails.DoesNotExist:
            if validateEmail(request.POST['email']):
                try:
                    e = NewsletterEmails(email = request.POST['email'])
                except DoesNotExist:
                    pass
                message = _(u"Email added.")
                type = "success"
                e.save()
            else:
                message = _(u"Wrong email")
                type = "error"

import re

def validateEmail(email):
    if len(email) > 6:
        if re.match('\b[\w\.-][email protected][\w\.-]+\.\w{2,4}\b', email) != None:
            return 1
    return 0
Answers:

UPDATE 2017: the code below is 7 years old and was since modified, fixed and expanded. For anyone wishing to do this now, the correct code lives around here: https://github.com/django/django/blob/master/django/core/validators.py#L168-L180

Here is part of django.core.validators you may find interesting 🙂

class EmailValidator(RegexValidator):

    def __call__(self, value):
        try:
            super(EmailValidator, self).__call__(value)
        except ValidationError, e:
            # Trivial case failed. Try for possible IDN domain-part
            if value and u'@' in value:
                parts = value.split(u'@')
                domain_part = parts[-1]
                try:
                    parts[-1] = parts[-1].encode('idna')
                except UnicodeError:
                    raise e
                super(EmailValidator, self).__call__(u'@'.join(parts))
            else:
                raise

email_re = re.compile(
    r"(^[-!#$%&'*+/=?^_`{}|~0-9A-Z]+(\.[-!#$%&'*+/=?^_`{}|~0-9A-Z]+)*"  # dot-atom
    r'|^"([
class EmailValidator(RegexValidator): def __call__(self, value): try: super(EmailValidator, self).__call__(value) except ValidationError, e: # Trivial case failed. Try for possible IDN domain-part if value and u'@' in value: parts = value.split(u'@') domain_part = parts[-1] try: parts[-1] = parts[-1].encode('idna') except UnicodeError: raise e super(EmailValidator, self).__call__(u'@'.join(parts)) else: raise email_re = re.compile( r"(^[-!#$%&'*+/=?^_`{}|~0-9A-Z]+(\.[-!#$%&'*+/=?^_`{}|~0-9A-Z]+)*" # dot-atom r'|^"([\001-\010\013\014\016-\037!#-\[\]-\177]|\\[\001-011\013\014\016-\177])*"' # quoted-string r')@(?:[A-Z0-9](?:[A-Z0-9-]{0,61}[A-Z0-9])?\.)+[A-Z]{2,6}\.?$', re.IGNORECASE) # domain validate_email = EmailValidator(email_re, _(u'Enter a valid e-mail address.'), 'invalid') 
1-0346-7!#-\[\]-7]|\[
class EmailValidator(RegexValidator): def __call__(self, value): try: super(EmailValidator, self).__call__(value) except ValidationError, e: # Trivial case failed. Try for possible IDN domain-part if value and u'@' in value: parts = value.split(u'@') domain_part = parts[-1] try: parts[-1] = parts[-1].encode('idna') except UnicodeError: raise e super(EmailValidator, self).__call__(u'@'.join(parts)) else: raise email_re = re.compile( r"(^[-!#$%&'*+/=?^_`{}|~0-9A-Z]+(\.[-!#$%&'*+/=?^_`{}|~0-9A-Z]+)*" # dot-atom r'|^"([\001-\010\013\014\016-\037!#-\[\]-\177]|\\[\001-011\013\014\016-\177])*"' # quoted-string r')@(?:[A-Z0-9](?:[A-Z0-9-]{0,61}[A-Z0-9])?\.)+[A-Z]{2,6}\.?$', re.IGNORECASE) # domain validate_email = EmailValidator(email_re, _(u'Enter a valid e-mail address.'), 'invalid') 
1-011346-7])*"' # quoted-string r')@(?:[A-Z0-9](?:[A-Z0-9-]{0,61}[A-Z0-9])?\.)+[A-Z]{2,6}\.?$', re.IGNORECASE) # domain validate_email = EmailValidator(email_re, _(u'Enter a valid e-mail address.'), 'invalid')

so if you don’t want to use forms and form fields, you can import email_re and use it in your function, or even better – import validate_email and use it, catching possible ValidationError.

def validateEmail( email ):
    from django.core.validators import validate_email
    from django.core.exceptions import ValidationError
    try:
        validate_email( email )
        return True
    except ValidationError:
        return False

And here is Mail::RFC822::Address regexp used in PERL, if you really need to be that paranoid.

Questions:
Answers:
from django.core.exceptions import ValidationError
from django.core.validators import validate_email
try:
    validate_email("[email protected]")
except ValidationError as e:
    print "oops! wrong email"
else:
    print "hooray! email is valid"

Questions:
Answers:

Ick, no, please, don’t try to validate email addresses yourself. It’s one of those things people never get right.

Your safest option, since you’re already using Django, is to just take advantage of its form validation for email. Per the docs ( http://docs.djangoproject.com/en/dev/ref/forms/fields/ ):

>>> from django import forms
>>> f = forms.EmailField()
>>> f.clean('[email protected]')
u'[email protected]'
>>> f.clean(u'[email protected]')
u'[email protected]'
>>> f.clean('invalid e-mail address')
...
ValidationError: [u'Enter a valid e-mail address.']

Questions:
Answers:

You got it wrong, but it is a task that you can’t do anyway. There is one and only one way to know if an RFC 2822 address is valid, and that is to send mail to it and get a response. Doing anything else doesn’t improve the information content of your datum by even a fractional bit.

You also screw the human factor and acceptance property, for when you give validateEmail my address of

[email protected]

and you tell me I’ve made an error, I tell your application goodbye.

Questions:
Answers:

Change your code from this:

re.match(‘\b[\w.-][email protected][\w.-]+.\w{2,4}\b’, email)

to this:

re.match(r’\b[\w.-][email protected][\w.-]+.\w{2,4}\b’, email)

works fine with me.

Questions:
Answers:

This regex will validate an email address with reasonable accuracy.

\w[\w\.-]*@\w[\w\.-]+\.\w+

It allows alphanumeric characters, _, . and -.