Re: [Zope] Email address validator?

24 Nov 2001

      Barry A. Warsaw wrote:
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"BE" == Bruce Eckel <Bruce@EckelObjects.com> writes:
BE> Worked like a charm! It turns out I was handing it an invalid
   BE> "from" email address.
BE> Which brings up another question -- is there a piece of code
   BE> that will validate email addresses somewhere? Seems like it
   BE> would be a common tool (I'll bet the spammers have it!).
Do you mean you want to find out if a string looks like a valid email
address, or that it actually successfully delivers to some end
destination?  The former is doable, the latter is exceedingly
difficult!
Mailman has the following bit of code, which accomplishes the goal set
out in its docstring <wink>:
I hadn't thought of looking through mailman.  Here's one I put together 
a couple of weeks ago that seems a bit more thorough...  

-- Jim Washington

# This is hacked from an existing script written in perl, licensed "public domain"
# The original perl script:  http://aspn.activestate.com/ASPN/Cookbook/Rx/Recipe/68432 2Nov2001
# author e-mail: tbyte@bolehmail.com

"""
Text of the perl script:

sub ValidEmailAddr { #check if e-mail address format is valid

my $mail = shift;                                                  #in form name@host

return 0 if ( $mail !~ /^[0-9a-zA-Z\.\-\_]+\@[0-9a-zA-Z\.\-]+$/ ); #characters allowed on name: 0-9a-Z-._ on host: 0-9a-Z-. on between: @
return 0 if ( $mail =~ /^[^0-9a-zA-Z]|[^0-9a-zA-Z]$/);             #must start or end with alpha or num
return 0 if ( $mail !~ /([0-9a-zA-Z]{1})\@./ );                    #name must end with alpha or num
return 0 if ( $mail !~ /.\@([0-9a-zA-Z]{1})/ );                    #host must start with alpha or num
return 0 if ( $mail =~ /.\.\-.|.\-\..|.\.\..|.\-\-./g );           #pair .- or -. or -- or .. not allowed
return 0 if ( $mail =~ /.\.\_.|.\-\_.|.\_\..|.\_\-.|.\_\_./g );    #pair ._ or -_ or _. or _- or __ not allowed
return 0 if ( $mail !~ /\.([a-zA-Z]{2,3})$/ );                     #host must end with '.' plus 2 or 3 alpha for TopLevelDomain (MUST be modified in future!)

return 1;
}

e-mail checker, checks whether an e-mail address is formatted properly.
usage:

from email_checker import valid_email

s = "string to be tested"
if valid_email(s):
  do_something()
else:
  do something_else()

"""

import re

rega = re.compile("^[0-9a-zA-Z\.\-\_]+\@[0-9a-zA-Z\.\-]+$") #failure a
regb = re.compile("^[^0-9a-zA-Z]|[^0-9a-zA-Z]$")            #failure b
regc = re.compile("([0-9a-zA-Z]{1})\@.")                    #failure c
regd = re.compile(".\@([0-9a-zA-Z]{1})")                    #failure d
rege = re.compile(".\.\-.|.\-\..|.\.\..|.\-\-.")            #failure e
regf = re.compile(".\.\_.|.\-\_.|.\_\..|.\_\-.|.\_\_.")     #failure f
regg = re.compile(".\.([a-zA-Z]{2,3})$|.\.([a-zA-Z]{2,4})$")#failure g

def valid_email(address, debug=None):
    fail = None
    if rega.search(address) is None:
        fail = 'a'
    elif regb.search(address) is not None:
        fail = 'b'
    elif regc.search(address) is None:
        fail = 'c'
    elif regd.search(address) is None:
        fail = 'd'
    elif rege.search(address) is not None:
        fail = 'e'
    elif regf.search(address) is not None:
        fail = 'f'
    elif regg.search(address) is None:
        fail = 'g'
    if fail is not None:
        if debug:
            return address,fail,None
        else:
            return None
    if debug:
        return address,1,1
    else:
        return 1

if __name__ == '__main__':
  #test a few:
  print valid_email('z+z.e@bun.org', debug=1)
  print valid_email('z.e@.org', debug=1)
  print valid_email('_az.e@bun.org', debug=1)
  print valid_email('e@b.g', debug=1)
  print valid_email('a_-.e@bun.org', debug=1)
  print valid_email('ok.computer@-bun.org', debug=1)
  print valid_email('ok.e@bun.org', debug=1)
  print valid_email('OK@bun.org', debug=1)
  print valid_email('t@bun.info', debug=1)
  print valid_email('my friend@bun.org', debug=1)
  print valid_email('my.friend.bun.org', debug=1)