I need some help with a regexp please

[codefire]

Hi,

I am trying to get a regexp to validate email addresses but can't get
it quite right. The problem is I can't quite find the regexp to deal
with ignoring the case james..ki**@fre d.com, which is not valid. Here's
my attempt, neither of my regexps work quite how I want:

import os
import re
 
s = 'Hi james..ki**@fred.com dr******@blarg.com ji*@home.com @@not
sc*****@home.space.com partridge in a pear tree'
r = re.compile(r'\w+\.?\w+@[^@\s]+\.\w+')
#r = re.compile(r'[a-z\-\.]+@[a-z\-\.]+')
 
addys = set()
for a in r.findall(s):
addys.add(a)
 
for a in sorted(addys):
print a
 

This gives:
dr******@blarg. com
ji*@home.com
ki**@fred.com <-- shouldn't be here :(
sc*****@home.sp ace.com

Nearly there but no cigar :)

I can't see the wood for the trees now :) Can anyone suggest a fix
please?

Thanks,
Tony

[richard.charts]

codefire wrote:

Hi,

I am trying to get a regexp to validate email addresses but can't get
it quite right. The problem is I can't quite find the regexp to deal
with ignoring the case james..ki**@fre d.com, which is not valid. Here's
my attempt, neither of my regexps work quite how I want:

import os
import re

s = 'Hi james..ki**@fred.com dr******@blarg.com ji*@home.com @@not
sc*****@home.space.com partridge in a pear tree'
r = re.compile(r'\w+\.?\w+@[^@\s]+\.\w+')
#r = re.compile(r'[a-z\-\.]+@[a-z\-\.]+')

addys = set()
for a in r.findall(s):
    addys.add(a)

for a in sorted(addys):
    print a
 

This gives:
dr******@blarg. com
ji*@home.com
ki**@fred.com <-- shouldn't be here :(
sc*****@home.sp ace.com

Nearly there but no cigar :)

I can't see the wood for the trees now :) Can anyone suggest a fix
please?

Thanks,
Tony

'[\w.]+@\w+(\.\w+)*'
Works for me, and SHOULD for you, but I haven't tested it all that
much.
Good luck.

[Neil Cerutti]

On 2006-09-21, codefire <to**********@g mail.comwrote:

I am trying to get a regexp to validate email addresses but
can't get it quite right. The problem is I can't quite find the
regexp to deal with ignoring the case james..ki**@fre d.com,
which is not valid. Here's my attempt, neither of my regexps
work quite how I want:

I suggest a websearch for email address validators instead of
writing of your own.

Here's a hit that looks useful:

http://aspn.activestate.com/ASPN/Coo...n/Recipe/66439

--
Neil Cerutti
Next Sunday Mrs. Vinson will be soloist for the morning service.
The pastor will then speak on "It's a Terrible Experience."
--Church Bulletin Blooper

[Steve Holden]

codefire wrote:

Hi,

I am trying to get a regexp to validate email addresses but can't get
it quite right. The problem is I can't quite find the regexp to deal
with ignoring the case james..ki**@fre d.com, which is not valid. Here's
my attempt, neither of my regexps work quite how I want:

import os
import re

s = 'Hi james..ki**@fred.com dr******@blarg.com ji*@home.com @@not
sc*****@home.space.com partridge in a pear tree'
r = re.compile(r'\w+\.?\w+@[^@\s]+\.\w+')
#r = re.compile(r'[a-z\-\.]+@[a-z\-\.]+')

addys = set()
for a in r.findall(s):
    addys.add(a)

for a in sorted(addys):
    print a
 

This gives:
dr******@blarg. com
ji*@home.com
ki**@fred.com <-- shouldn't be here :(
sc*****@home.sp ace.com

Nearly there but no cigar :)

I can't see the wood for the trees now :) Can anyone suggest a fix
please?

The problem is that your pattern doesn't start out by confirming that
it's either at the start of a line or after whitespace. You could do
this with a "look-behind assertion" if you wanted.

regards
Steve
--
Steve Holden [phone] [phone]
Holden Web LLC/Ltd http://www.holdenweb.com
Skype: holdenweb http://holdenweb.blogspot.com
Recent Ramblings http://del.icio.us/steve.holden

[codefire]

Hi,

thanks for the advice guys.

Well took the kids swimming, watched some TV, read your hints and
within a few minutes had this:

r = re.compile(r'[^.\w]\w+\.?\w+@[^@\s]+\.\w+')

This works for me. That is if you have an invalid email such as
tony..bATblah.c om it will reject it (note the double dots).

Anyway, now know a little more about regexps :)

Thanks again for the hints,

Tony

[John Machin]

codefire wrote:

Hi,

thanks for the advice guys.

Well took the kids swimming, watched some TV, read your hints and
within a few minutes had this:

r = re.compile(r'[^.\w]\w+\.?\w+@[^@\s]+\.\w+')

This works for me. That is if you have an invalid email such as
tony..bATblah.c om it will reject it (note the double dots).

Anyway, now know a little more about regexps :)

A little more is unfortunately not enough. The best advice you got was
to use an existing e-mail address validator. The definition of a valid
e-mail address is complicated. You may care to check out "Mastering
Regular Expressions" by Jeffery Friedl. In the first edition, at least
(I haven't looked at the 2nd), he works through assembling a 4700+ byte
regex for validating e-mail addresses. Yes, that's 4KB. It's the best
advertisement for *not* using regexes for a task like that that I've
ever seen.

Cheers,
John

[Ben Finney]

"John Machin" <sj******@lexic on.netwrites:

A little more is unfortunately not enough. The best advice you got was
to use an existing e-mail address validator. The definition of a valid
e-mail address is complicated. You may care to check out "Mastering
Regular Expressions" by Jeffery Friedl. In the first edition, at least
(I haven't looked at the 2nd), he works through assembling a 4700+ byte
regex for validating e-mail addresses. Yes, that's 4KB. It's the best
advertisement for *not* using regexes for a task like that that I've
ever seen.

The best advice I've seen when people ask "How do I validate whether
an email address is valid?" was "Try sending mail to it".

It's both Pythonic, and truly the best way. If you actually want to
confirm, don't try to validate it statically; *use* the email address,
and check the result. Send an email to that address, and don't use it
any further unless you get a reply saying "yes, this is the right
address to use" from the recipient.

The sending system's mail transport agent, not regular expressions,
determines which part is the domain to send the mail to.

The domain name system, not regular expressions, determines what
domains are valid, and what host should receive mail for that domain.

Most especially, the receiving mail system, not regular expressions,
determines what local-parts are valid.

--
\ "I believe in making the world safe for our children, but not |
`\ our children's children, because I don't think children should |
_o__) be having sex." -- Jack Handey |
Ben Finney

[Steve Holden]

Ben Finney wrote:

"John Machin" <sj******@lexic on.netwrites:

>>A little more is unfortunately not enough. The best advice you got was
to use an existing e-mail address validator. The definition of a valid
e-mail address is complicated. You may care to check out "Mastering
Regular Expressions" by Jeffery Friedl. In the first edition, at least
(I haven't looked at the 2nd), he works through assembling a 4700+ byte
regex for validating e-mail addresses. Yes, that's 4KB. It's the best
advertiseme nt for *not* using regexes for a task like that that I've
ever seen.

The best advice I've seen when people ask "How do I validate whether
an email address is valid?" was "Try sending mail to it".

That only applies if it's a likely-looking email address. If someone
asks me to send mail to "splurge.!#$%*& ^from@thingie?> <{}_)" I will
probably assume that it isn't worth my time trying.

If the email looks syntactically correct, *then* it's worth further
validation by trying a delivery attempt.

It's both Pythonic, and truly the best way. If you actually want to
confirm, don't try to validate it statically; *use* the email address,
and check the result. Send an email to that address, and don't use it
any further unless you get a reply saying "yes, this is the right
address to use" from the recipient.

This is a rather scatter-shot approach. Many possibilities can be
properly eliminated by judicious lexical checks before delivery is
considered.

The sending system's mail transport agent, not regular expressions,
determines which part is the domain to send the mail to.

The domain name system, not regular expressions, determines what
domains are valid, and what host should receive mail for that domain.

Most especially, the receiving mail system, not regular expressions,
determines what local-parts are valid.

Nevertheless, I am *not* going to try delivery to (for example) a
non-local address that doesn't contain an "at@ sign.

regards
Steve
--
Steve Holden [phone] [phone]
Holden Web LLC/Ltd http://www.holdenweb.com
Skype: holdenweb http://holdenweb.blogspot.com
Recent Ramblings http://del.icio.us/steve.holden

[Ben Finney]

Steve Holden <st***@holdenwe b.comwrites:

Ben Finney wrote:

The best advice I've seen when people ask "How do I validate
whether an email address is valid?" was "Try sending mail to it".

That only applies if it's a likely-looking email address. If someone
asks me to send mail to "splurge.!#$%*& ^from@thingie?> <{}_)" I will
probably assume that it isn't worth my time trying.

You, as a human, can possibly make that decision, if you don't care
about turning away someone who *does* have such an email address. How
can an algorithm do so? There are many valid email addresses that look
as bizarre as the example you gave.

The sending system's mail transport agent, not regular
expressions, determines which part is the domain to send the mail
to.

The domain name system, not regular expressions, determines what
domains are valid, and what host should receive mail for that
domain.

Most especially, the receiving mail system, not regular
expressions, determines what local-parts are valid.

Nevertheless, I am *not* going to try delivery to (for example) a
non-local address that doesn't contain an "at@ sign.

Would you try delivery to an email address that contains two or more
"@" symbols? If not, you will be denying delivery to valid RFC2821
addresses.

This is, of course, something you're entitled to do. But you've then
consciously chosen not to use "is the email address valid?" as your
criterion, and the original request for such validation becomes moot.

--
\ "During my service in the United States Congress, I took the |
`\ initiative in creating the Internet." -- Al Gore |
_o__) |
Ben Finney

[Ant]

John Machin wrote:
....

A little more is unfortunately not enough. The best advice you got was
to use an existing e-mail address validator.

We got bitten by this at the last place I worked - we were using a
regex email validator (from Microsoft IIRC), and we kept having
problems with specific email addresses from Ireland. There are stack of
Irish email addresses out there of the form paddy.o'reilly@ domain -
perfectly valid email address, but doesn't satisfy the usual naive
versions of regex validators.

We use an even worse validator at my current job, but the feeling the
management have (not one I agree with) is that unusual email addresses,
whilst perhaps valid, are uncommon enough not to worry about....