Sto creando un'app su Google App Engine. Sono incredibilmente nuovo su Python e negli ultimi 3 giorni ho battuto la testa contro il seguente problema.

Ho una classe per rappresentare un feed RSS e in questa classe ho un metodo chiamato setUrl. L'input per questo metodo è un URL.

Sto cercando di utilizzare il modulo re python per convalidare l'RFC 3986 Reg-ex ( http://www.ietf.org/rfc/rfc3986.txt )

Di seguito è riportato un frammento che dovrebbe funzionare?

p = re.compile('^(([^:/?#]+):)?(//([^/?#]*))?([^?#]*)(\?([^#]*))?(#(.*))?')
m = p.match(url)
if m:
  self.url = url
  return url

Un modo semplice per analizzare (e convalidare) gli URL è il modulourlparse ( py2 , py3 ).

Una regex è troppo faticosa.

Non esiste un metodo di "convalida" perché quasi tutto è un URL valido. Ci sono alcune regole di punteggiatura per suddividerlo. In assenza di punteggiatura, hai ancora un URL valido.

Controllare attentamente l'RFC e vedere se è possibile creare un URL "non valido". Le regole sono molto flessibili.

Ad esempio :::::è un URL valido. Il percorso è":::::" . Un nome di file piuttosto stupido, ma un nome di file valido.

Inoltre, /////è un URL valido. Il netloc ("hostname") è "". Il percorso è "///". Di nuovo, stupido. Valido anche. Questo URL si normalizza in"///" quale è l'equivalente.

Qualcosa di simile "bad://///worse/////"è perfettamente valido. Muto ma valido.

Linea di fondo . Analizzalo e guarda i pezzi per vedere se in qualche modo non piacciono.

Vuoi che lo schema sia sempre "http"? Vuoi che il netloc sia sempre "www.somename.somedomain"? Vuoi che il percorso sia simile a unix? O come finestre? Vuoi rimuovere la stringa di query? O conservarlo?

Queste non sono convalide specificate da RFC. Queste sono convalide uniche per la tua applicazione.

Ecco la regexp completa per analizzare un URL.

(?:http://(?:(?:(?:(?:(?:[a-zA-Z\d](?:(?:[a-zA-Z\d]|-)*[a-zA-Z\d])?)\.
)*(?:[a-zA-Z](?:(?:[a-zA-Z\d]|-)*[a-zA-Z\d])?))|(?:(?:\d+)(?:\.(?:\d+)
){3}))(?::(?:\d+))?)(?:/(?:(?:(?:(?:[a-zA-Z\d$\-_.+!*'(),]|(?:%[a-fA-F
\d]{2}))|[;:@&=])*)(?:/(?:(?:(?:[a-zA-Z\d$\-_.+!*'(),]|(?:%[a-fA-F\d]{
2}))|[;:@&=])*))*)(?:\?(?:(?:(?:[a-zA-Z\d$\-_.+!*'(),]|(?:%[a-fA-F\d]{
2}))|[;:@&=])*))?)?)|(?:ftp://(?:(?:(?:(?:(?:[a-zA-Z\d$\-_.+!*'(),]|(?
:%[a-fA-F\d]{2}))|[;?&=])*)(?::(?:(?:(?:[a-zA-Z\d$\-_.+!*'(),]|(?:%[a-
fA-F\d]{2}))|[;?&=])*))?@)?(?:(?:(?:(?:(?:[a-zA-Z\d](?:(?:[a-zA-Z\d]|-
)*[a-zA-Z\d])?)\.)*(?:[a-zA-Z](?:(?:[a-zA-Z\d]|-)*[a-zA-Z\d])?))|(?:(?
:\d+)(?:\.(?:\d+)){3}))(?::(?:\d+))?))(?:/(?:(?:(?:(?:[a-zA-Z\d$\-_.+!
*'(),]|(?:%[a-fA-F\d]{2}))|[?:@&=])*)(?:/(?:(?:(?:[a-zA-Z\d$\-_.+!*'()
,]|(?:%[a-fA-F\d]{2}))|[?:@&=])*))*)(?:;type=[AIDaid])?)?)|(?:news:(?:
(?:(?:(?:[a-zA-Z\d$\-_.+!*'(),]|(?:%[a-fA-F\d]{2}))|[;/?:&=])+@(?:(?:(
?:(?:[a-zA-Z\d](?:(?:[a-zA-Z\d]|-)*[a-zA-Z\d])?)\.)*(?:[a-zA-Z](?:(?:[
a-zA-Z\d]|-)*[a-zA-Z\d])?))|(?:(?:\d+)(?:\.(?:\d+)){3})))|(?:[a-zA-Z](
?:[a-zA-Z\d]|[_.+-])*)|\*))|(?:nntp://(?:(?:(?:(?:(?:[a-zA-Z\d](?:(?:[
a-zA-Z\d]|-)*[a-zA-Z\d])?)\.)*(?:[a-zA-Z](?:(?:[a-zA-Z\d]|-)*[a-zA-Z\d
])?))|(?:(?:\d+)(?:\.(?:\d+)){3}))(?::(?:\d+))?)/(?:[a-zA-Z](?:[a-zA-Z
\d]|[_.+-])*)(?:/(?:\d+))?)|(?:telnet://(?:(?:(?:(?:(?:[a-zA-Z\d$\-_.+
!*'(),]|(?:%[a-fA-F\d]{2}))|[;?&=])*)(?::(?:(?:(?:[a-zA-Z\d$\-_.+!*'()
,]|(?:%[a-fA-F\d]{2}))|[;?&=])*))?@)?(?:(?:(?:(?:(?:[a-zA-Z\d](?:(?:[a
-zA-Z\d]|-)*[a-zA-Z\d])?)\.)*(?:[a-zA-Z](?:(?:[a-zA-Z\d]|-)*[a-zA-Z\d]
)?))|(?:(?:\d+)(?:\.(?:\d+)){3}))(?::(?:\d+))?))/?)|(?:gopher://(?:(?:
(?:(?:(?:[a-zA-Z\d](?:(?:[a-zA-Z\d]|-)*[a-zA-Z\d])?)\.)*(?:[a-zA-Z](?:
(?:[a-zA-Z\d]|-)*[a-zA-Z\d])?))|(?:(?:\d+)(?:\.(?:\d+)){3}))(?::(?:\d+
))?)(?:/(?:[a-zA-Z\d$\-_.+!*'(),;/?:@&=]|(?:%[a-fA-F\d]{2}))(?:(?:(?:[
a-zA-Z\d$\-_.+!*'(),;/?:@&=]|(?:%[a-fA-F\d]{2}))*)(?:%09(?:(?:(?:[a-zA
-Z\d$\-_.+!*'(),]|(?:%[a-fA-F\d]{2}))|[;:@&=])*)(?:%09(?:(?:[a-zA-Z\d$
\-_.+!*'(),;/?:@&=]|(?:%[a-fA-F\d]{2}))*))?)?)?)?)|(?:wais://(?:(?:(?:
(?:(?:[a-zA-Z\d](?:(?:[a-zA-Z\d]|-)*[a-zA-Z\d])?)\.)*(?:[a-zA-Z](?:(?:
[a-zA-Z\d]|-)*[a-zA-Z\d])?))|(?:(?:\d+)(?:\.(?:\d+)){3}))(?::(?:\d+))?
)/(?:(?:[a-zA-Z\d$\-_.+!*'(),]|(?:%[a-fA-F\d]{2}))*)(?:(?:/(?:(?:[a-zA
-Z\d$\-_.+!*'(),]|(?:%[a-fA-F\d]{2}))*)/(?:(?:[a-zA-Z\d$\-_.+!*'(),]|(
?:%[a-fA-F\d]{2}))*))|\?(?:(?:(?:[a-zA-Z\d$\-_.+!*'(),]|(?:%[a-fA-F\d]
{2}))|[;:@&=])*))?)|(?:mailto:(?:(?:[a-zA-Z\d$\-_.+!*'(),;/?:@&=]|(?:%
[a-fA-F\d]{2}))+))|(?:file://(?:(?:(?:(?:(?:[a-zA-Z\d](?:(?:[a-zA-Z\d]
|-)*[a-zA-Z\d])?)\.)*(?:[a-zA-Z](?:(?:[a-zA-Z\d]|-)*[a-zA-Z\d])?))|(?:
(?:\d+)(?:\.(?:\d+)){3}))|localhost)?/(?:(?:(?:(?:[a-zA-Z\d$\-_.+!*'()
,]|(?:%[a-fA-F\d]{2}))|[?:@&=])*)(?:/(?:(?:(?:[a-zA-Z\d$\-_.+!*'(),]|(
?:%[a-fA-F\d]{2}))|[?:@&=])*))*))|(?:prospero://(?:(?:(?:(?:(?:[a-zA-Z
\d](?:(?:[a-zA-Z\d]|-)*[a-zA-Z\d])?)\.)*(?:[a-zA-Z](?:(?:[a-zA-Z\d]|-)
*[a-zA-Z\d])?))|(?:(?:\d+)(?:\.(?:\d+)){3}))(?::(?:\d+))?)/(?:(?:(?:(?
:[a-zA-Z\d$\-_.+!*'(),]|(?:%[a-fA-F\d]{2}))|[?:@&=])*)(?:/(?:(?:(?:[a-
zA-Z\d$\-_.+!*'(),]|(?:%[a-fA-F\d]{2}))|[?:@&=])*))*)(?:(?:;(?:(?:(?:[
a-zA-Z\d$\-_.+!*'(),]|(?:%[a-fA-F\d]{2}))|[?:@&])*)=(?:(?:(?:[a-zA-Z\d
$\-_.+!*'(),]|(?:%[a-fA-F\d]{2}))|[?:@&])*)))*)|(?:ldap://(?:(?:(?:(?:
(?:(?:[a-zA-Z\d](?:(?:[a-zA-Z\d]|-)*[a-zA-Z\d])?)\.)*(?:[a-zA-Z](?:(?:
[a-zA-Z\d]|-)*[a-zA-Z\d])?))|(?:(?:\d+)(?:\.(?:\d+)){3}))(?::(?:\d+))?
))?/(?:(?:(?:(?:(?:(?:(?:[a-zA-Z\d]|%(?:3\d|[46][a-fA-F\d]|[57][Aa\d])
)|(?:%20))+|(?:OID|oid)\.(?:(?:\d+)(?:\.(?:\d+))*))(?:(?:%0[Aa])?(?:%2
0)*)=(?:(?:%0[Aa])?(?:%20)*))?(?:(?:[a-zA-Z\d$\-_.+!*'(),]|(?:%[a-fA-F
\d]{2}))*))(?:(?:(?:%0[Aa])?(?:%20)*)\+(?:(?:%0[Aa])?(?:%20)*)(?:(?:(?
:(?:(?:[a-zA-Z\d]|%(?:3\d|[46][a-fA-F\d]|[57][Aa\d]))|(?:%20))+|(?:OID
|oid)\.(?:(?:\d+)(?:\.(?:\d+))*))(?:(?:%0[Aa])?(?:%20)*)=(?:(?:%0[Aa])
?(?:%20)*))?(?:(?:[a-zA-Z\d$\-_.+!*'(),]|(?:%[a-fA-F\d]{2}))*)))*)(?:(
?:(?:(?:%0[Aa])?(?:%20)*)(?:[;,])(?:(?:%0[Aa])?(?:%20)*))(?:(?:(?:(?:(
?:(?:[a-zA-Z\d]|%(?:3\d|[46][a-fA-F\d]|[57][Aa\d]))|(?:%20))+|(?:OID|o
id)\.(?:(?:\d+)(?:\.(?:\d+))*))(?:(?:%0[Aa])?(?:%20)*)=(?:(?:%0[Aa])?(
?:%20)*))?(?:(?:[a-zA-Z\d$\-_.+!*'(),]|(?:%[a-fA-F\d]{2}))*))(?:(?:(?:
%0[Aa])?(?:%20)*)\+(?:(?:%0[Aa])?(?:%20)*)(?:(?:(?:(?:(?:[a-zA-Z\d]|%(
?:3\d|[46][a-fA-F\d]|[57][Aa\d]))|(?:%20))+|(?:OID|oid)\.(?:(?:\d+)(?:
\.(?:\d+))*))(?:(?:%0[Aa])?(?:%20)*)=(?:(?:%0[Aa])?(?:%20)*))?(?:(?:[a
-zA-Z\d$\-_.+!*'(),]|(?:%[a-fA-F\d]{2}))*)))*))*(?:(?:(?:%0[Aa])?(?:%2
0)*)(?:[;,])(?:(?:%0[Aa])?(?:%20)*))?)(?:\?(?:(?:(?:(?:[a-zA-Z\d$\-_.+
!*'(),]|(?:%[a-fA-F\d]{2}))+)(?:,(?:(?:[a-zA-Z\d$\-_.+!*'(),]|(?:%[a-f
A-F\d]{2}))+))*)?)(?:\?(?:base|one|sub)(?:\?(?:((?:[a-zA-Z\d$\-_.+!*'(
),;/?:@&=]|(?:%[a-fA-F\d]{2}))+)))?)?)?)|(?:(?:z39\.50[rs])://(?:(?:(?
:(?:(?:[a-zA-Z\d](?:(?:[a-zA-Z\d]|-)*[a-zA-Z\d])?)\.)*(?:[a-zA-Z](?:(?
:[a-zA-Z\d]|-)*[a-zA-Z\d])?))|(?:(?:\d+)(?:\.(?:\d+)){3}))(?::(?:\d+))
?)(?:/(?:(?:(?:[a-zA-Z\d$\-_.+!*'(),]|(?:%[a-fA-F\d]{2}))+)(?:\+(?:(?:
[a-zA-Z\d$\-_.+!*'(),]|(?:%[a-fA-F\d]{2}))+))*(?:\?(?:(?:[a-zA-Z\d$\-_
.+!*'(),]|(?:%[a-fA-F\d]{2}))+))?)?(?:;esn=(?:(?:[a-zA-Z\d$\-_.+!*'(),
]|(?:%[a-fA-F\d]{2}))+))?(?:;rs=(?:(?:[a-zA-Z\d$\-_.+!*'(),]|(?:%[a-fA
-F\d]{2}))+)(?:\+(?:(?:[a-zA-Z\d$\-_.+!*'(),]|(?:%[a-fA-F\d]{2}))+))*)
?))|(?:cid:(?:(?:(?:[a-zA-Z\d$\-_.+!*'(),]|(?:%[a-fA-F\d]{2}))|[;?:@&=
])*))|(?:mid:(?:(?:(?:[a-zA-Z\d$\-_.+!*'(),]|(?:%[a-fA-F\d]{2}))|[;?:@
&=])*)(?:/(?:(?:(?:[a-zA-Z\d$\-_.+!*'(),]|(?:%[a-fA-F\d]{2}))|[;?:@&=]
)*))?)|(?:vemmi://(?:(?:(?:(?:(?:[a-zA-Z\d](?:(?:[a-zA-Z\d]|-)*[a-zA-Z
\d])?)\.)*(?:[a-zA-Z](?:(?:[a-zA-Z\d]|-)*[a-zA-Z\d])?))|(?:(?:\d+)(?:\
.(?:\d+)){3}))(?::(?:\d+))?)(?:/(?:(?:(?:[a-zA-Z\d$\-_.+!*'(),]|(?:%[a
-fA-F\d]{2}))|[/?:@&=])*)(?:(?:;(?:(?:(?:[a-zA-Z\d$\-_.+!*'(),]|(?:%[a
-fA-F\d]{2}))|[/?:@&])*)=(?:(?:(?:[a-zA-Z\d$\-_.+!*'(),]|(?:%[a-fA-F\d
]{2}))|[/?:@&])*))*))?)|(?:imap://(?:(?:(?:(?:(?:(?:(?:[a-zA-Z\d$\-_.+
!*'(),]|(?:%[a-fA-F\d]{2}))|[&=~])+)(?:(?:;[Aa][Uu][Tt][Hh]=(?:\*|(?:(
?:(?:[a-zA-Z\d$\-_.+!*'(),]|(?:%[a-fA-F\d]{2}))|[&=~])+))))?)|(?:(?:;[
Aa][Uu][Tt][Hh]=(?:\*|(?:(?:(?:[a-zA-Z\d$\-_.+!*'(),]|(?:%[a-fA-F\d]{2
}))|[&=~])+)))(?:(?:(?:(?:[a-zA-Z\d$\-_.+!*'(),]|(?:%[a-fA-F\d]{2}))|[
&=~])+))?))@)?(?:(?:(?:(?:(?:[a-zA-Z\d](?:(?:[a-zA-Z\d]|-)*[a-zA-Z\d])
?)\.)*(?:[a-zA-Z](?:(?:[a-zA-Z\d]|-)*[a-zA-Z\d])?))|(?:(?:\d+)(?:\.(?:
\d+)){3}))(?::(?:\d+))?))/(?:(?:(?:(?:(?:(?:[a-zA-Z\d$\-_.+!*'(),]|(?:
%[a-fA-F\d]{2}))|[&=~:@/])+)?;[Tt][Yy][Pp][Ee]=(?:[Ll](?:[Ii][Ss][Tt]|
[Ss][Uu][Bb])))|(?:(?:(?:(?:[a-zA-Z\d$\-_.+!*'(),]|(?:%[a-fA-F\d]{2}))
|[&=~:@/])+)(?:\?(?:(?:(?:[a-zA-Z\d$\-_.+!*'(),]|(?:%[a-fA-F\d]{2}))|[
&=~:@/])+))?(?:(?:;[Uu][Ii][Dd][Vv][Aa][Ll][Ii][Dd][Ii][Tt][Yy]=(?:[1-
9]\d*)))?)|(?:(?:(?:(?:[a-zA-Z\d$\-_.+!*'(),]|(?:%[a-fA-F\d]{2}))|[&=~
:@/])+)(?:(?:;[Uu][Ii][Dd][Vv][Aa][Ll][Ii][Dd][Ii][Tt][Yy]=(?:[1-9]\d*
)))?(?:/;[Uu][Ii][Dd]=(?:[1-9]\d*))(?:(?:/;[Ss][Ee][Cc][Tt][Ii][Oo][Nn
]=(?:(?:(?:[a-zA-Z\d$\-_.+!*'(),]|(?:%[a-fA-F\d]{2}))|[&=~:@/])+)))?))
)?)|(?:nfs:(?:(?://(?:(?:(?:(?:(?:[a-zA-Z\d](?:(?:[a-zA-Z\d]|-)*[a-zA-
Z\d])?)\.)*(?:[a-zA-Z](?:(?:[a-zA-Z\d]|-)*[a-zA-Z\d])?))|(?:(?:\d+)(?:
\.(?:\d+)){3}))(?::(?:\d+))?)(?:(?:/(?:(?:(?:(?:(?:[a-zA-Z\d\$\-_.!~*'
(),])|(?:%[a-fA-F\d]{2})|[:@&=+])*)(?:/(?:(?:(?:[a-zA-Z\d\$\-_.!~*'(),
])|(?:%[a-fA-F\d]{2})|[:@&=+])*))*)?)))?)|(?:/(?:(?:(?:(?:(?:[a-zA-Z\d
\$\-_.!~*'(),])|(?:%[a-fA-F\d]{2})|[:@&=+])*)(?:/(?:(?:(?:[a-zA-Z\d\$\
-_.!~*'(),])|(?:%[a-fA-F\d]{2})|[:@&=+])*))*)?))|(?:(?:(?:(?:(?:[a-zA-
Z\d\$\-_.!~*'(),])|(?:%[a-fA-F\d]{2})|[:@&=+])*)(?:/(?:(?:(?:[a-zA-Z\d
\$\-_.!~*'(),])|(?:%[a-fA-F\d]{2})|[:@&=+])*))*)?)))

Data la sua complessità, penso che dovresti andare nel modo urlparse.

Per completezza, ecco lo pseudo-BNF della regex sopra (come documentazione):

; La forma generica di un URL è:

genericurl = scheme ":" schemepart

; Schemi predefiniti specifici sono definiti qui; nuovi schemi
; può essere registrato con IANA

url = httpurl | ftpurl | newsurl |
                 nntpurl | telneturl | gopherurl |
                 waisurl | mailtourl | fileurl |
                 prosperourl | otherurl

; i nuovi schemi seguono la sintassi generale
otherurl = genericurl

; lo schema è in minuscolo; gli interpreti dovrebbero usare il case-ignore
schema = 1 * [lowalpha | cifra | "+" | "-" | "." ]
schemepart = * xchar | ip-schemepart


; Schemi URL per protocolli basati su IP:

ip-schemepart = "//" login ["/" urlpath]

login = porta host [utente [":" password] "@"]
hostport = host [":" port]
host = hostname | hostnumber
hostname = * [etichetta dominio "." ] toplabel
domainlabel = alphadigit | alphadigit * [alphadigit | "-"] alphadigit
toplabel = alpha | alpha * [alphadigit | "-"] alphadigit
alphadigit = alpha | cifra
hostnumber = cifre "." cifre "." cifre "." cifre
porta = cifre
utente = * [uchar | ";" | "?" | "&" | "="]
password = * [uchar | ";" | "?" | "&" | "="]
urlpath = * xchar; dipende dal protocollo vedere la sezione 3.1

; Gli schemi predefiniti:

; FTP (vedi anche RFC959)

ftpurl = "ftp: //" login ["/" fpath ["; type =" ftptype]]
fpath = fsegment * ["/" fsegment]
fsegment = * [uchar | "?" | ":" | "@" | "&" | "="]
ftptype = "A" | "Io" | "D" | "a" | "i" | "d"

; FILE

fileurl = "file: //" [host | "localhost"] "/" fpath

; HTTP

httpurl = "http: //" hostport ["/" hpath ["?" ricerca ]]
hpath = hsegment * ["/" hsegment]
hsegment = * [uchar | ";" | ":" | "@" | "&" | "="]
ricerca = * [uchar | ";" | ":" | "@" | "&" | "="]

; GOPHER (vedi anche RFC1436)

gopherurl = "gopher: //" hostport [/ [gtype [selector
                 ["% 09" cerca ["% 09" gopher + _string]]]]]
gtype = xchar
selettore = * xchar
gopher + _string = * xchar

; MAILTO (vedi anche RFC822)

mailtourl = "mailto:" encoded822addr
encoded822addr = 1 * xchar; ulteriormente definito in RFC822

; NEWS (vedi anche RFC1036)

newsurl = "notizie:" grouppart
grouppart = "*" | gruppo | articolo
gruppo = alpha * [alpha | cifra | "-" | "." | "+" | "_"]
articolo = 1 * [uchar | ";" | "/" | "?" | ":" | "&" | "="] "@" host

; NNTP (vedere anche RFC977)

nntpurl = "nntp: //" hostport "/" gruppo ["/" cifre]

; TELNET

telneturl = "telnet: //" login ["/"]

; WAIS (vedere anche RFC1625)

waisurl = waisdatabase | waisindex | waisdoc
waisdatabase = "wais: //" hostport "/" database
waisindex = "wais: //" hostport "/" database "?" ricerca
waisdoc = "wais: //" hostport "/" database "/" wtype "/" wpath
database = * uchar
wtype = * uchar
wpath = * uchar

; PROSPERO

prosperourl = "prospero: //" hostport "/" ppath * [fieldpec]
ppath = psegment * ["/" psegment]
psegment = * [uchar | "?" | ":" | "@" | "&" | "="]
fieldpec = ";" fieldname "=" fieldvalue
fieldname = * [uchar | "?" | ":" | "@" | "&"]
fieldvalue = * [uchar | "?" | ":" | "@" | "&"]

; Definizioni varie

lowalpha = "a" | "b" | "c" | "d" | "e" | "f" | "g" | "h" |
                 "i" | "j" | "k" | "l" | "m" | "n" | "o" | "p" |
                 "q" | "r" | "s" | "t" | "u" | "v" | "w" | "x" |
                 "y" | "z"
hialpha = "A" | "B" | "C" | "D" | "E" | "F" | "G" | "H" | "Io" |
                 "J" | "K" | "L" | "M" | "N" | "O" | "P" | "Q" | "R" |
                 "S" | "T" | "U" | "V" | "W" | "X" | "Y" | "Z"
alpha = lowalpha | hialpha
cifra = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" |
                 "8" | "9"
sicuro = "$" | "-" | "_" | "." | "+"
extra = "!" | "*" | "'" | "(" | ")" | ","
national = "{" | "}" | "|" | "\" | "^" | "~" | "[" | "]" | "` "
punteggiatura = "" | "#" | "%" |


riservato = ";" | "/" | "?" | ":" | "@" | "&" | "="
hex = cifra | "A" | "B" | "C" | "D" | "E" | "F" |
                 "a" | "b" | "c" | "d" | "e" | "f"
escape = "%" hex hex

senza riserva = alpha | cifra | sicuro | extra
uchar = senza riserva | fuga
xchar = senza riserva | riservato | fuga
cifre = 1 * cifra

Sto usando quello usato da Django e sembra funzionare abbastanza bene:

def is_valid_url(url):
    import re
    regex = re.compile(
        r'^https?://'  # http:// or https://
        r'(?:(?:[A-Z0-9](?:[A-Z0-9-]{0,61}[A-Z0-9])?\.)+[A-Z]{2,6}\.?|'  # domain...
        r'localhost|'  # localhost...
        r'\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})' # ...or ip
        r'(?::\d+)?'  # optional port
        r'(?:/?|[/?]\S+)$', re.IGNORECASE)
    return url is not None and regex.search(url)

Puoi sempre controllare l'ultima versione qui: https://github.com/django/django/blob/master/django/core/validators.py#L74

Lo ammetto, trovo la tua espressione regolare del tutto incomprensibile. Mi chiedo se potresti usare urlparse invece? Qualcosa di simile a:

pieces = urlparse.urlparse(url)
assert all([pieces.scheme, pieces.netloc])
assert set(pieces.netloc) <= set(string.letters + string.digits + '-.')  # and others?
assert pieces.scheme in ['http', 'https', 'ftp']  # etc.

Potrebbe essere più lento e forse ti mancheranno le condizioni, ma a me sembra molto più facile da leggere ed eseguire il debug di un'espressione regolare per gli URL .

urlparseaccetta abbastanza felicemente URL non validi, è più una libreria che divide le stringhe che qualsiasi tipo di validatore. Per esempio:

from urlparse import urlparse
urlparse('http://----')
# returns: ParseResult(scheme='http', netloc='----', path='', params='', query='', fragment='')

A seconda della situazione, potrebbe andare bene.

Se ti fidi principalmente dei dati e vuoi solo verificare che il protocollo sia HTTP, allora urlparseè perfetto.

Se vuoi che l'URL sia effettivamente un URL legale, usa la ridicola regex

Se vuoi assicurarti che sia un indirizzo web reale,

import urllib
try:
    urllib.urlopen(url)
except IOError:
    print "Not a real URL"

http://pypi.python.org/pypi/rfc3987 fornisce espressioni regolari per coerenza con le regole in RFC 3986 e RFC 3987 (cioè, non con regole specifiche dello schema).

Una regexp per IRI_reference è:

(?P<scheme>[a-zA-Z][a-zA-Z0-9+.-]*):(?://(?P<iauthority>(?:(?P<iuserinfo>(?:(?:[
a-zA-Z0-9._~-]|[\xa0-\ud7ff\uf900-\ufdcf\ufdf0-\uffef\U00010000-\U0001fffd\U0002
0000-\U0002fffd\U00030000-\U0003fffd\U00040000-\U0004fffd\U00050000-\U0005fffd\U
00060000-\U0006fffd\U00070000-\U0007fffd\U00080000-\U0008fffd\U00090000-\U0009ff
fd\U000a0000-\U000afffd\U000b0000-\U000bfffd\U000c0000-\U000cfffd\U000d0000-\U00
0dfffd\U000e1000-\U000efffd])|%[0-9A-F][0-9A-F]|[!$&'()*+,;=]|:)*)@)?(?P<ihost>\
\[(?:(?:[0-9A-F]{1,4}:){6}(?:[0-9A-F]{1,4}:[0-9A-F]{1,4}|(?:(?:(?:25[0-5]|2[0-4]
[0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)))|::(?:[0
-9A-F]{1,4}:){5}(?:[0-9A-F]{1,4}:[0-9A-F]{1,4}|(?:(?:(?:25[0-5]|2[0-4][0-9]|[01]
?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)))|[0-9A-F]{1,4}?::(
?:[0-9A-F]{1,4}:){4}(?:[0-9A-F]{1,4}:[0-9A-F]{1,4}|(?:(?:(?:25[0-5]|2[0-4][0-9]|
[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)))|(?:(?:[0-9A-F
]{1,4}:)?[0-9A-F]{1,4})?::(?:[0-9A-F]{1,4}:){3}(?:[0-9A-F]{1,4}:[0-9A-F]{1,4}|(?
:(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[
0-9][0-9]?)))|(?:(?:[0-9A-F]{1,4}:){,2}[0-9A-F]{1,4})?::(?:[0-9A-F]{1,4}:){2}(?:
[0-9A-F]{1,4}:[0-9A-F]{1,4}|(?:(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3
}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)))|(?:(?:[0-9A-F]{1,4}:){,3}[0-9A-F]{1,
4})?::(?:[0-9A-F]{1,4}:)(?:[0-9A-F]{1,4}:[0-9A-F]{1,4}|(?:(?:(?:25[0-5]|2[0-4][0
-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)))|(?:(?:[0-
9A-F]{1,4}:){,4}[0-9A-F]{1,4})?::(?:[0-9A-F]{1,4}:[0-9A-F]{1,4}|(?:(?:(?:25[0-5]
|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)))|
(?:(?:[0-9A-F]{1,4}:){,5}[0-9A-F]{1,4})?::[0-9A-F]{1,4}|(?:(?:[0-9A-F]{1,4}:){,6
}[0-9A-F]{1,4})?::|v[0-9A-F]+\\.(?:[a-zA-Z0-9_.~-]|[!$&'()*+,;=]|:)+)\\]|(?:(?:(
?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][
0-9]?))|(?:(?:[a-zA-Z0-9._~-]|[\xa0-\ud7ff\uf900-\ufdcf\ufdf0-\uffef\U00010000-\
U0001fffd\U00020000-\U0002fffd\U00030000-\U0003fffd\U00040000-\U0004fffd\U000500
00-\U0005fffd\U00060000-\U0006fffd\U00070000-\U0007fffd\U00080000-\U0008fffd\U00
090000-\U0009fffd\U000a0000-\U000afffd\U000b0000-\U000bfffd\U000c0000-\U000cfffd
\U000d0000-\U000dfffd\U000e1000-\U000efffd])|%[0-9A-F][0-9A-F]|[!$&'()*+,;=])*)(
?::(?P<port>[0-9]*))?)(?P<ipath>(?:/(?:(?:[a-zA-Z0-9._~-]|[\xa0-\ud7ff\uf900-\uf
dcf\ufdf0-\uffef\U00010000-\U0001fffd\U00020000-\U0002fffd\U00030000-\U0003fffd\
U00040000-\U0004fffd\U00050000-\U0005fffd\U00060000-\U0006fffd\U00070000-\U0007f
ffd\U00080000-\U0008fffd\U00090000-\U0009fffd\U000a0000-\U000afffd\U000b0000-\U0
00bfffd\U000c0000-\U000cfffd\U000d0000-\U000dfffd\U000e1000-\U000efffd])|%[0-9A-
F][0-9A-F]|[!$&'()*+,;=]|:|@)*)*)|(?P<ipath>/(?:(?:(?:[a-zA-Z0-9._~-]|[\xa0-\ud7
ff\uf900-\ufdcf\ufdf0-\uffef\U00010000-\U0001fffd\U00020000-\U0002fffd\U00030000
-\U0003fffd\U00040000-\U0004fffd\U00050000-\U0005fffd\U00060000-\U0006fffd\U0007
0000-\U0007fffd\U00080000-\U0008fffd\U00090000-\U0009fffd\U000a0000-\U000afffd\U
000b0000-\U000bfffd\U000c0000-\U000cfffd\U000d0000-\U000dfffd\U000e1000-\U000eff
fd])|%[0-9A-F][0-9A-F]|[!$&'()*+,;=]|:|@)+(?:/(?:(?:[a-zA-Z0-9._~-]|[\xa0-\ud7ff
\uf900-\ufdcf\ufdf0-\uffef\U00010000-\U0001fffd\U00020000-\U0002fffd\U00030000-\
U0003fffd\U00040000-\U0004fffd\U00050000-\U0005fffd\U00060000-\U0006fffd\U000700
00-\U0007fffd\U00080000-\U0008fffd\U00090000-\U0009fffd\U000a0000-\U000afffd\U00
0b0000-\U000bfffd\U000c0000-\U000cfffd\U000d0000-\U000dfffd\U000e1000-\U000efffd
])|%[0-9A-F][0-9A-F]|[!$&'()*+,;=]|:|@)*)*)?)|(?P<ipath>(?:(?:[a-zA-Z0-9._~-]|[\
xa0-\ud7ff\uf900-\ufdcf\ufdf0-\uffef\U00010000-\U0001fffd\U00020000-\U0002fffd\U
00030000-\U0003fffd\U00040000-\U0004fffd\U00050000-\U0005fffd\U00060000-\U0006ff
fd\U00070000-\U0007fffd\U00080000-\U0008fffd\U00090000-\U0009fffd\U000a0000-\U00
0afffd\U000b0000-\U000bfffd\U000c0000-\U000cfffd\U000d0000-\U000dfffd\U000e1000-
\U000efffd])|%[0-9A-F][0-9A-F]|[!$&'()*+,;=]|:|@)+(?:/(?:(?:[a-zA-Z0-9._~-]|[\xa
0-\ud7ff\uf900-\ufdcf\ufdf0-\uffef\U00010000-\U0001fffd\U00020000-\U0002fffd\U00
030000-\U0003fffd\U00040000-\U0004fffd\U00050000-\U0005fffd\U00060000-\U0006fffd
\U00070000-\U0007fffd\U00080000-\U0008fffd\U00090000-\U0009fffd\U000a0000-\U000a
fffd\U000b0000-\U000bfffd\U000c0000-\U000cfffd\U000d0000-\U000dfffd\U000e1000-\U
000efffd])|%[0-9A-F][0-9A-F]|[!$&'()*+,;=]|:|@)*)*)|(?P<ipath>))(?:\\?(?P<iquery
>(?:(?:(?:[a-zA-Z0-9._~-]|[\xa0-\ud7ff\uf900-\ufdcf\ufdf0-\uffef\U00010000-\U000
1fffd\U00020000-\U0002fffd\U00030000-\U0003fffd\U00040000-\U0004fffd\U00050000-\
U0005fffd\U00060000-\U0006fffd\U00070000-\U0007fffd\U00080000-\U0008fffd\U000900
00-\U0009fffd\U000a0000-\U000afffd\U000b0000-\U000bfffd\U000c0000-\U000cfffd\U00
0d0000-\U000dfffd\U000e1000-\U000efffd])|%[0-9A-F][0-9A-F]|[!$&'()*+,;=]|:|@)|[\
ue000-\uf8ff\U000f0000-\U000ffffd\U00100000-\U0010fffd]|/|\\?)*))?(?:\\#(?P<ifra
gment>(?:(?:(?:[a-zA-Z0-9._~-]|[\xa0-\ud7ff\uf900-\ufdcf\ufdf0-\uffef\U00010000-
\U0001fffd\U00020000-\U0002fffd\U00030000-\U0003fffd\U00040000-\U0004fffd\U00050
000-\U0005fffd\U00060000-\U0006fffd\U00070000-\U0007fffd\U00080000-\U0008fffd\U0
0090000-\U0009fffd\U000a0000-\U000afffd\U000b0000-\U000bfffd\U000c0000-\U000cfff
d\U000d0000-\U000dfffd\U000e1000-\U000efffd])|%[0-9A-F][0-9A-F]|[!$&'()*+,;=]|:|
@)|/|\\?)*))?|(?:(?://(?P<iauthority>(?:(?P<iuserinfo>(?:(?:[a-zA-Z0-9._~-]|[\xa
0-\ud7ff\uf900-\ufdcf\ufdf0-\uffef\U00010000-\U0001fffd\U00020000-\U0002fffd\U00
030000-\U0003fffd\U00040000-\U0004fffd\U00050000-\U0005fffd\U00060000-\U0006fffd
\U00070000-\U0007fffd\U00080000-\U0008fffd\U00090000-\U0009fffd\U000a0000-\U000a
fffd\U000b0000-\U000bfffd\U000c0000-\U000cfffd\U000d0000-\U000dfffd\U000e1000-\U
000efffd])|%[0-9A-F][0-9A-F]|[!$&'()*+,;=]|:)*)@)?(?P<ihost>\\[(?:(?:[0-9A-F]{1,
4}:){6}(?:[0-9A-F]{1,4}:[0-9A-F]{1,4}|(?:(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-
9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)))|::(?:[0-9A-F]{1,4}:){5}(?:
[0-9A-F]{1,4}:[0-9A-F]{1,4}|(?:(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3
}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)))|[0-9A-F]{1,4}?::(?:[0-9A-F]{1,4}:){4
}(?:[0-9A-F]{1,4}:[0-9A-F]{1,4}|(?:(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\
.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)))|(?:(?:[0-9A-F]{1,4}:)?[0-9A-F]{1
,4})?::(?:[0-9A-F]{1,4}:){3}(?:[0-9A-F]{1,4}:[0-9A-F]{1,4}|(?:(?:(?:25[0-5]|2[0-
4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)))|(?:(?
:[0-9A-F]{1,4}:){,2}[0-9A-F]{1,4})?::(?:[0-9A-F]{1,4}:){2}(?:[0-9A-F]{1,4}:[0-9A
-F]{1,4}|(?:(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][
0-9]|[01]?[0-9][0-9]?)))|(?:(?:[0-9A-F]{1,4}:){,3}[0-9A-F]{1,4})?::(?:[0-9A-F]{1
,4}:)(?:[0-9A-F]{1,4}:[0-9A-F]{1,4}|(?:(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]
?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)))|(?:(?:[0-9A-F]{1,4}:){,4}[0-
9A-F]{1,4})?::(?:[0-9A-F]{1,4}:[0-9A-F]{1,4}|(?:(?:(?:25[0-5]|2[0-4][0-9]|[01]?[
0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)))|(?:(?:[0-9A-F]{1,4}
:){,5}[0-9A-F]{1,4})?::[0-9A-F]{1,4}|(?:(?:[0-9A-F]{1,4}:){,6}[0-9A-F]{1,4})?::|
v[0-9A-F]+\\.(?:[a-zA-Z0-9_.~-]|[!$&'()*+,;=]|:)+)\\]|(?:(?:(?:25[0-5]|2[0-4][0-
9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?))|(?:(?:[a-zA
-Z0-9._~-]|[\xa0-\ud7ff\uf900-\ufdcf\ufdf0-\uffef\U00010000-\U0001fffd\U00020000
-\U0002fffd\U00030000-\U0003fffd\U00040000-\U0004fffd\U00050000-\U0005fffd\U0006
0000-\U0006fffd\U00070000-\U0007fffd\U00080000-\U0008fffd\U00090000-\U0009fffd\U
000a0000-\U000afffd\U000b0000-\U000bfffd\U000c0000-\U000cfffd\U000d0000-\U000dff
fd\U000e1000-\U000efffd])|%[0-9A-F][0-9A-F]|[!$&'()*+,;=])*)(?::(?P<port>[0-9]*)
)?)(?P<ipath>(?:/(?:(?:[a-zA-Z0-9._~-]|[\xa0-\ud7ff\uf900-\ufdcf\ufdf0-\uffef\U0
0010000-\U0001fffd\U00020000-\U0002fffd\U00030000-\U0003fffd\U00040000-\U0004fff
d\U00050000-\U0005fffd\U00060000-\U0006fffd\U00070000-\U0007fffd\U00080000-\U000
8fffd\U00090000-\U0009fffd\U000a0000-\U000afffd\U000b0000-\U000bfffd\U000c0000-\
U000cfffd\U000d0000-\U000dfffd\U000e1000-\U000efffd])|%[0-9A-F][0-9A-F]|[!$&'()*
+,;=]|:|@)*)*)|(?P<ipath>/(?:(?:(?:[a-zA-Z0-9._~-]|[\xa0-\ud7ff\uf900-\ufdcf\ufd
f0-\uffef\U00010000-\U0001fffd\U00020000-\U0002fffd\U00030000-\U0003fffd\U000400
00-\U0004fffd\U00050000-\U0005fffd\U00060000-\U0006fffd\U00070000-\U0007fffd\U00
080000-\U0008fffd\U00090000-\U0009fffd\U000a0000-\U000afffd\U000b0000-\U000bfffd
\U000c0000-\U000cfffd\U000d0000-\U000dfffd\U000e1000-\U000efffd])|%[0-9A-F][0-9A
-F]|[!$&'()*+,;=]|:|@)+(?:/(?:(?:[a-zA-Z0-9._~-]|[\xa0-\ud7ff\uf900-\ufdcf\ufdf0
-\uffef\U00010000-\U0001fffd\U00020000-\U0002fffd\U00030000-\U0003fffd\U00040000
-\U0004fffd\U00050000-\U0005fffd\U00060000-\U0006fffd\U00070000-\U0007fffd\U0008
0000-\U0008fffd\U00090000-\U0009fffd\U000a0000-\U000afffd\U000b0000-\U000bfffd\U
000c0000-\U000cfffd\U000d0000-\U000dfffd\U000e1000-\U000efffd])|%[0-9A-F][0-9A-F
]|[!$&'()*+,;=]|:|@)*)*)?)|(?P<ipath>(?:(?:[a-zA-Z0-9._~-]|[\xa0-\ud7ff\uf900-\u
fdcf\ufdf0-\uffef\U00010000-\U0001fffd\U00020000-\U0002fffd\U00030000-\U0003fffd
\U00040000-\U0004fffd\U00050000-\U0005fffd\U00060000-\U0006fffd\U00070000-\U0007
fffd\U00080000-\U0008fffd\U00090000-\U0009fffd\U000a0000-\U000afffd\U000b0000-\U
000bfffd\U000c0000-\U000cfffd\U000d0000-\U000dfffd\U000e1000-\U000efffd])|%[0-9A
-F][0-9A-F]|[!$&'()*+,;=]|@)+(?:/(?:(?:[a-zA-Z0-9._~-]|[\xa0-\ud7ff\uf900-\ufdcf
\ufdf0-\uffef\U00010000-\U0001fffd\U00020000-\U0002fffd\U00030000-\U0003fffd\U00
040000-\U0004fffd\U00050000-\U0005fffd\U00060000-\U0006fffd\U00070000-\U0007fffd
\U00080000-\U0008fffd\U00090000-\U0009fffd\U000a0000-\U000afffd\U000b0000-\U000b
fffd\U000c0000-\U000cfffd\U000d0000-\U000dfffd\U000e1000-\U000efffd])|%[0-9A-F][
0-9A-F]|[!$&'()*+,;=]|:|@)*)*)|(?P<ipath>))(?:\\?(?P<iquery>(?:(?:(?:[a-zA-Z0-9.
_~-]|[\xa0-\ud7ff\uf900-\ufdcf\ufdf0-\uffef\U00010000-\U0001fffd\U00020000-\U000
2fffd\U00030000-\U0003fffd\U00040000-\U0004fffd\U00050000-\U0005fffd\U00060000-\
U0006fffd\U00070000-\U0007fffd\U00080000-\U0008fffd\U00090000-\U0009fffd\U000a00
00-\U000afffd\U000b0000-\U000bfffd\U000c0000-\U000cfffd\U000d0000-\U000dfffd\U00
0e1000-\U000efffd])|%[0-9A-F][0-9A-F]|[!$&'()*+,;=]|:|@)|[\ue000-\uf8ff\U000f000
0-\U000ffffd\U00100000-\U0010fffd]|/|\\?)*))?(?:\\#(?P<ifragment>(?:(?:(?:[a-zA-
Z0-9._~-]|[\xa0-\ud7ff\uf900-\ufdcf\ufdf0-\uffef\U00010000-\U0001fffd\U00020000-
\U0002fffd\U00030000-\U0003fffd\U00040000-\U0004fffd\U00050000-\U0005fffd\U00060
000-\U0006fffd\U00070000-\U0007fffd\U00080000-\U0008fffd\U00090000-\U0009fffd\U0
00a0000-\U000afffd\U000b0000-\U000bfffd\U000c0000-\U000cfffd\U000d0000-\U000dfff
d\U000e1000-\U000efffd])|%[0-9A-F][0-9A-F]|[!$&'()*+,;=]|:|@)|/|\\?)*))?)

In una riga:

(?P<scheme>[a-zA-Z][a-zA-Z0-9+.-]*):(?://(?P<iauthority>(?:(?P<iuserinfo>(?:(?:[a-zA-Z0-9._~-]|[\xa0-\ud7ff\uf900-\ufdcf\ufdf0-\uffef\U00010000-\U0001fffd\U00020000-\U0002fffd\U00030000-\U0003fffd\U00040000-\U0004fffd\U00050000-\U0005fffd\U00060000-\U0006fffd\U00070000-\U0007fffd\U00080000-\U0008fffd\U00090000-\U0009fffd\U000a0000-\U000afffd\U000b0000-\U000bfffd\U000c0000-\U000cfffd\U000d0000-\U000dfffd\U000e1000-\U000efffd])|%[0-9A-F][0-9A-F]|[!$&'()*+,;=]|:)*)@)?(?P<ihost>\\[(?:(?:[0-9A-F]{1,4}:){6}(?:[0-9A-F]{1,4}:[0-9A-F]{1,4}|(?:(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)))|::(?:[0-9A-F]{1,4}:){5}(?:[0-9A-F]{1,4}:[0-9A-F]{1,4}|(?:(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)))|[0-9A-F]{1,4}?::(?:[0-9A-F]{1,4}:){4}(?:[0-9A-F]{1,4}:[0-9A-F]{1,4}|(?:(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)))|(?:(?:[0-9A-F]{1,4}:)?[0-9A-F]{1,4})?::(?:[0-9A-F]{1,4}:){3}(?:[0-9A-F]{1,4}:[0-9A-F]{1,4}|(?:(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)))|(?:(?:[0-9A-F]{1,4}:){,2}[0-9A-F]{1,4})?::(?:[0-9A-F]{1,4}:){2}(?:[0-9A-F]{1,4}:[0-9A-F]{1,4}|(?:(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)))|(?:(?:[0-9A-F]{1,4}:){,3}[0-9A-F]{1,4})?::(?:[0-9A-F]{1,4}:)(?:[0-9A-F]{1,4}:[0-9A-F]{1,4}|(?:(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)))|(?:(?:[0-9A-F]{1,4}:){,4}[0-9A-F]{1,4})?::(?:[0-9A-F]{1,4}:[0-9A-F]{1,4}|(?:(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)))|(?:(?:[0-9A-F]{1,4}:){,5}[0-9A-F]{1,4})?::[0-9A-F]{1,4}|(?:(?:[0-9A-F]{1,4}:){,6}[0-9A-F]{1,4})?::|v[0-9A-F]+\\.(?:[a-zA-Z0-9_.~-]|[!$&'()*+,;=]|:)+)\\]|(?:(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?))|(?:(?:[a-zA-Z0-9._~-]|[\xa0-\ud7ff\uf900-\ufdcf\ufdf0-\uffef\U00010000-\U0001fffd\U00020000-\U0002fffd\U00030000-\U0003fffd\U00040000-\U0004fffd\U00050000-\U0005fffd\U00060000-\U0006fffd\U00070000-\U0007fffd\U00080000-\U0008fffd\U00090000-\U0009fffd\U000a0000-\U000afffd\U000b0000-\U000bfffd\U000c0000-\U000cfffd\U000d0000-\U000dfffd\U000e1000-\U000efffd])|%[0-9A-F][0-9A-F]|[!$&'()*+,;=])*)(?::(?P<port>[0-9]*))?)(?P<ipath>(?:/(?:(?:[a-zA-Z0-9._~-]|[\xa0-\ud7ff\uf900-\ufdcf\ufdf0-\uffef\U00010000-\U0001fffd\U00020000-\U0002fffd\U00030000-\U0003fffd\U00040000-\U0004fffd\U00050000-\U0005fffd\U00060000-\U0006fffd\U00070000-\U0007fffd\U00080000-\U0008fffd\U00090000-\U0009fffd\U000a0000-\U000afffd\U000b0000-\U000bfffd\U000c0000-\U000cfffd\U000d0000-\U000dfffd\U000e1000-\U000efffd])|%[0-9A-F][0-9A-F]|[!$&'()*+,;=]|:|@)*)*)|(?P<ipath>/(?:(?:(?:[a-zA-Z0-9._~-]|[\xa0-\ud7ff\uf900-\ufdcf\ufdf0-\uffef\U00010000-\U0001fffd\U00020000-\U0002fffd\U00030000-\U0003fffd\U00040000-\U0004fffd\U00050000-\U0005fffd\U00060000-\U0006fffd\U00070000-\U0007fffd\U00080000-\U0008fffd\U00090000-\U0009fffd\U000a0000-\U000afffd\U000b0000-\U000bfffd\U000c0000-\U000cfffd\U000d0000-\U000dfffd\U000e1000-\U000efffd])|%[0-9A-F][0-9A-F]|[!$&'()*+,;=]|:|@)+(?:/(?:(?:[a-zA-Z0-9._~-]|[\xa0-\ud7ff\uf900-\ufdcf\ufdf0-\uffef\U00010000-\U0001fffd\U00020000-\U0002fffd\U00030000-\U0003fffd\U00040000-\U0004fffd\U00050000-\U0005fffd\U00060000-\U0006fffd\U00070000-\U0007fffd\U00080000-\U0008fffd\U00090000-\U0009fffd\U000a0000-\U000afffd\U000b0000-\U000bfffd\U000c0000-\U000cfffd\U000d0000-\U000dfffd\U000e1000-\U000efffd])|%[0-9A-F][0-9A-F]|[!$&'()*+,;=]|:|@)*)*)?)|(?P<ipath>(?:(?:[a-zA-Z0-9._~-]|[\xa0-\ud7ff\uf900-\ufdcf\ufdf0-\uffef\U00010000-\U0001fffd\U00020000-\U0002fffd\U00030000-\U0003fffd\U00040000-\U0004fffd\U00050000-\U0005fffd\U00060000-\U0006fffd\U00070000-\U0007fffd\U00080000-\U0008fffd\U00090000-\U0009fffd\U000a0000-\U000afffd\U000b0000-\U000bfffd\U000c0000-\U000cfffd\U000d0000-\U000dfffd\U000e1000-\U000efffd])|%[0-9A-F][0-9A-F]|[!$&'()*+,;=]|:|@)+(?:/(?:(?:[a-zA-Z0-9._~-]|[\xa0-\ud7ff\uf900-\ufdcf\ufdf0-\uffef\U00010000-\U0001fffd\U00020000-\U0002fffd\U00030000-\U0003fffd\U00040000-\U0004fffd\U00050000-\U0005fffd\U00060000-\U0006fffd\U00070000-\U0007fffd\U00080000-\U0008fffd\U00090000-\U0009fffd\U000a0000-\U000afffd\U000b0000-\U000bfffd\U000c0000-\U000cfffd\U000d0000-\U000dfffd\U000e1000-\U000efffd])|%[0-9A-F][0-9A-F]|[!$&'()*+,;=]|:|@)*)*)|(?P<ipath>))(?:\\?(?P<iquery>(?:(?:(?:[a-zA-Z0-9._~-]|[\xa0-\ud7ff\uf900-\ufdcf\ufdf0-\uffef\U00010000-\U0001fffd\U00020000-\U0002fffd\U00030000-\U0003fffd\U00040000-\U0004fffd\U00050000-\U0005fffd\U00060000-\U0006fffd\U00070000-\U0007fffd\U00080000-\U0008fffd\U00090000-\U0009fffd\U000a0000-\U000afffd\U000b0000-\U000bfffd\U000c0000-\U000cfffd\U000d0000-\U000dfffd\U000e1000-\U000efffd])|%[0-9A-F][0-9A-F]|[!$&'()*+,;=]|:|@)|[\ue000-\uf8ff\U000f0000-\U000ffffd\U00100000-\U0010fffd]|/|\\?)*))?(?:\\#(?P<ifragment>(?:(?:(?:[a-zA-Z0-9._~-]|[\xa0-\ud7ff\uf900-\ufdcf\ufdf0-\uffef\U00010000-\U0001fffd\U00020000-\U0002fffd\U0003000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0e1000-\U000efffd])|%[0-9A-F][0-9A-F]|[!$&'()*+,;=]|:|@)|[\ue000-\uf8ff\U000f0000-\U000ffffd\U00100000-\U0010fffd]|/|\\?)*))?(?:\\#(?P<ifragment>(?:(?:(?:[a-zA-Z0-9._~-]|[\xa0-\ud7ff\uf900-\ufdcf\ufdf0-\uffef\U00010000-\U0001fffd\U00020000-\U0002fffd\U00030000-\U0003fffd\U00040000-\U0004fffd\U00050000-\U0005fffd\U00060000-\U0006fffd\U00070000-\U0007fffd\U00080000-\U0008fffd\U00090000-\U0009fffd\U000a0000-\U000afffd\U000b0000-\U000bfffd\U000c0000-\U000cfffd\U000d0000-\U000dfffd\U000e1000-\U000efffd])|%[0-9A-F][0-9A-F]|[!$&'()*+,;=]|:|@)|/|\\?)*))?)

nota - Lepl non è più mantenuto o supportato.

RFC 3696 definisce "best practice" per la convalida degli URL: http://www.faqs.org/rfcs/rfc3696.html

L'ultima versione di Lepl (una libreria parser Python) include un'implementazione di RFC 3696. La useresti qualcosa del tipo:

from lepl.apps.rfc3696 import Email, HttpUrl

# compile the validators (do once at start of program)
valid_email = Email()
valid_http_url = HttpUrl()

# use the validators (as often as you like)
if valid_email(some_email):
    # email is ok
else:
    # email is bad
if valid_http_url(some_url):
    # url is ok
else:
    # url is bad

Sebbene i validatori siano definiti in Lepl, che è un parser discendente ricorsivo, sono in gran parte compilati internamente in espressioni regolari. Ciò combina il meglio di entrambi i mondi: una definizione (relativamente) facile da leggere che può essere verificata rispetto alla RFC 3696 e un'implementazione efficiente. C'è un post sul mio blog che mostra come questo semplifica il parser - http://www.acooke.org/cute/LEPLOptimi0.html

Lepl è disponibile su http://www.acooke.org/lepl e il modulo RFC 3696 è documentato su http://www.acooke.org/lepl/rfc3696.html

Questo è completamente nuovo in questa versione, quindi potrebbe contenere bug. Per favore contattami se hai problemi e li risolverò al più presto. Grazie.

Al giorno d'oggi, nel 90% dei casi, se lavori con URL in Python, probabilmente usi le richieste python. Da qui la domanda: perché non riutilizzare la convalida dell'URL dalle richieste?

from requests.models import PreparedRequest
import requests.exceptions


def check_url(url):
    prepared_request = PreparedRequest()
    try:
        prepared_request.prepare_url(url, None)
        return prepared_request.url
    except requests.exceptions.MissingSchema, e:
        raise SomeException

Caratteristiche:

• Non reinventare la ruota
• ASCIUTTO
• Lavoro offline
• Risorsa minima

La regex fornita deve corrispondere a qualsiasi URL del modulo http://www.ietf.org/rfc/rfc3986.txt ; e lo fa quando viene testato nell'interprete python.

Che formato hanno gli URL che hai riscontrato problemi di analisi?

Ho dovuto farlo molte volte nel corso degli anni e finisco sempre per copiare l'espressione regolare di qualcun altro che ci ha pensato molto più di quanto io voglia pensarci.

Detto questo, c'è una regex nel codice dei moduli Django che dovrebbe fare il trucco:

http://code.djangoproject.com/browser/django/trunk/django/forms/fields.py#L534

regex di convalida dell'URL di Django modificato:

import re

ul = '\u00a1-\uffff'  # unicode letters range (must not be a raw string)

# IP patterns 
ipv4_re = r'(?:25[0-5]|2[0-4]\d|[0-1]?\d?\d)(?:\.(?:25[0-5]|2[0-4]\d|[0-1]?\d?\d)){3}' 
ipv6_re = r'\[[0-9a-f:\.]+\]'

# Host patterns 
hostname_re = r'[a-z' + ul + r'0-9](?:[a-z' + ul + r'0-9-]{0,61}[a-z' + ul + r'0-9])?'
domain_re = r'(?:\.(?!-)[a-z' + ul + r'0-9-]{1,63}(?<!-))*' # domain names have max length of 63 characters
tld_re = ( 
    r'\.'                                # dot 
    r'(?!-)'                             # can't start with a dash 
    r'(?:[a-z' + ul + '-]{2,63}'         # domain label 
    r'|xn--[a-z0-9]{1,59})'              # or punycode label 
    r'(?<!-)'                            # can't end with a dash 
    r'\.?'                               # may have a trailing dot 
) 
host_re = '(' + hostname_re + domain_re + tld_re + '|localhost)'

regex = re.compile( 
    r'^(?:http|ftp)s?://' # http(s):// or ftp(s)://
    r'(?:\S+(?::\S*)?@)?'  # user:pass authentication 
    r'(?:' + ipv4_re + '|' + ipv6_re + '|' + host_re + ')' # localhost or ip
    r'(?::\d{2,5})?'  # optional port
    r'(?:[/?#][^\s]*)?'  # resource path
    r'\Z', re.IGNORECASE)

fonte: https://github.com/django/django/blob/master/django/core/validators.py#L74

urlfinders = [
    re.compile("([0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3}|(((news|telnet|nttp|file|http|ftp|https)://)|(www|ftp)[-A-Za-z0-9]*\\.)[-A-Za-z0-9\\.]+)(:[0-9]*)?/[-A-Za-z0-9_\\$\\.\\+\\!\\*\\(\\),;:@&=\\?/~\\#\\%]*[^]'\\.}>\\),\\\"]"),
    re.compile("([0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3}|(((news|telnet|nttp|file|http|ftp|https)://)|(www|ftp)[-A-Za-z0-9]*\\.)[-A-Za-z0-9\\.]+)(:[0-9]*)?"),
    re.compile("(~/|/|\\./)([-A-Za-z0-9_\\$\\.\\+\\!\\*\\(\\),;:@&=\\?/~\\#\\%]|\\\\
)+"),
    re.compile("'\\<((mailto:)|)[-A-Za-z0-9\\.]+@[-A-Za-z0-9\\.]+"),
]

NOTA: per quanto brutto possa sembrare nel tuo browser, copia e incolla e la formattazione dovrebbe essere buona

Trovato nelle mailing list di python e usato per gnome-terminal

fonte: http://mail.python.org/pipermail/python-list/2007-January/595436.html