I have a regexp in Perl that converts the last digit of an ip address to
'9'. This is a very particular case so I don't want to go off on a
tangent of IP octets.
( my $s = $str ) =~ s/((\d+\.){3})\d+/${1}9/ ;
While I can do this in Python which accomplishes the same thing:
ip = ip[ :-1 ]
ip =+ '9'
I'm more interested, for my own edification in non-trivial cases, in how
one would convert the Perl RE to a Python RE that use groups. I am
somewhat familiar using the group method from the re package but I
wanted to know if there was a one-line solution.
Thank you. 6 2986
On Oct 19, 5:47*pm, Bruno Desthuilliers
<bdesth.quelque ch...@free.quel quepart.frwrote :
Pat a écrit :
I have a regexp in Perl that converts the last digit of an ip address to
*'9'. *This is a very particular case so I don't want to go off on a
tangent of IP octets.
*( my $s = $str ) =~ s/((\d+\.){3})\d+/${1}9/ ;
While I can do this in Python which accomplishes the same thing:
ip = ip[ :-1 ]
ip =+ '9'
or:
ip = ip[:-1]+"9"
I'm more interested, for my own edification in non-trivial cases, in how
one would convert the Perl RE to a Python RE that use groups. *I am
somewhat familiar using the group method from the re package but I
wanted to know if there was a one-line solution.
Is that what you want ?
*>>re.sub(r'^(( (\d+)\.){3})\d+ $', "\g<1>9", "192.168.1. 1")
'192.168.1.9'
>re.sub(r'^(((\ d+)\.){3})\d+$' , "\g<1>9", "192.168.1.100" )
'192.168.1.9'
The regular expression changes the last sequence of digits to
"9" ("192.168.1.100 " ="192.168.1. 9") but the other code replaces the
last digit ("192.168.1.100 " ="192.168.1.109 ").
MRAB:
The regular expression changes the last sequence of digits to
"9" ("192.168.1.100 " ="192.168.1. 9") but the other code replaces the
last digit ("192.168.1.100 " ="192.168.1.109 ").
Uhmm, this is a possible alternative:
>>s = " 192.168.1.100 " ".".join(s.st rip().split("." )[:3]) + ".9"
'192.168.1.9'
Bye,
bearophile
MRAB a écrit :
On Oct 19, 5:47 pm, Bruno Desthuilliers
<bdesth.quelque ch...@free.quel quepart.frwrote :
>Pat a écrit :
(snip)
>>ip = ip[ :-1 ] ip =+ '9'
or:
ip = ip[:-1]+"9"
(snip)
> >>re.sub(r'^((( \d+)\.){3})\d+$ ', "\g<1>9", "192.168.1. 1")
'192.168.1.9 '
>>>>re.sub(r'^( ((\d+)\.){3})\d +$', "\g<1>9", "192.168.1.100" )
'192.168.1.9 '
The regular expression changes the last sequence of digits to
"9" ("192.168.1.100 " ="192.168.1. 9") but the other code replaces the
last digit ("192.168.1.100 " ="192.168.1.109 ").
Mmm - yes, true.
ip = ".".join(ip.spl it('.')[0:3] + ['9'])
Bruno Desthuilliers wrote:
Pat a écrit :
>I have a regexp in Perl that converts the last digit of an ip address to '9'. This is a very particular case so I don't want to go off on a tangent of IP octets.
( my $s = $str ) =~ s/((\d+\.){3})\d+/${1}9/ ;
While I can do this in Python which accomplishes the same thing:
ip = ip[ :-1 ] ip =+ '9'
or:
ip = ip[:-1]+"9"
Yes! That's exactly what I was looking for.
>
>I'm more interested, for my own edification in non-trivial cases, in how one would convert the Perl RE to a Python RE that use groups. I am somewhat familiar using the group method from the re package but I wanted to know if there was a one-line solution.
Is that what you want ?
>>re.sub(r'^((( \d+)\.){3})\d+$ ', "\g<1>9", "192.168.1. 1")
'192.168.1.9'
>>>re.sub(r'^(( (\d+)\.){3})\d+ $', "\g<1>9", "192.168.1.100" )
'192.168.1.9'
Ah-hah! That's how one uses groups. It's beautiful. I couldn't find
that in my books. Thank you very, very much!
At first, I thought that using RE's in Python was going to be more
difficult than Perl. A lot of my Perl code makes heavy use of RE
searching and substitution.
I will never, ever write another line of Perl code as long as I live.
Pat a écrit :
Bruno Desthuilliers wrote:
>Pat a écrit :
>>I have a regexp in Perl that converts the last digit of an ip address to '9'. This is a very particular case so I don't want to go off on a tangent of IP octets.
( my $s = $str ) =~ s/((\d+\.){3})\d+/${1}9/ ;
While I can do this in Python which accomplishes the same thing:
ip = ip[ :-1 ] ip =+ '9'
or:
ip = ip[:-1]+"9"
Yes! That's exactly what I was looking for.
Perhaps not - cf MRAB's post earlier in this thread and bearophile's answer.
While this was a straightforward one-liner version of your own code, it
doesn't behave like the re version : this one only replace the last
_character_, while the re version replaces the last _group_. If you want
the re version's behaviour, use this instead:
ip = ".".join(ip.spl it('.')[0:3] + ['9'])
>>
>>I'm more interested, for my own edification in non-trivial cases, in how one would convert the Perl RE to a Python RE that use groups. I am somewhat familiar using the group method from the re package but I wanted to know if there was a one-line solution.
Is that what you want ?
> >>re.sub(r'^((( \d+)\.){3})\d+$ ', "\g<1>9", "192.168.1. 1")
'192.168.1.9 '
>>>>re.sub(r'^( ((\d+)\.){3})\d +$', "\g<1>9", "192.168.1.100" )
'192.168.1.9 '
Ah-hah! That's how one uses groups. It's beautiful. I couldn't find
that in my books.
Did you look at the FineManual(tm) ?-)
>
At first, I thought that using RE's in Python was going to be more
difficult than Perl. A lot of my Perl code makes heavy use of RE
searching and substitution.
Well... Python's re module makes for a bit more verbose code, and I'm
not sure all of the perl's regexps features are implemented. But that's
still quite enough to shoot yourself in the foot IMHO !-)
Now while regexps are a must-have in a programmer's toolbox, you can
already do quite a few things just using slicing and string methods. I
highly recommend you read the relevant doc.
I will never, ever write another line of Perl code as long as I live.
Hmmm... Never say "never again" ?-)
Bruno Desthuilliers wrote:
MRAB a écrit :
>On Oct 19, 5:47 pm, Bruno Desthuilliers <bdesth.quelqu ech...@free.que lquepart.frwrot e:
>>Pat a écrit :
(snip)
>>>ip = ip[ :-1 ] ip =+ '9' or:
ip = ip[:-1]+"9"
(snip)
>> >>re.sub(r'^((( \d+)\.){3})\d+$ ', "\g<1>9", "192.168.1. 1") '192.168.1. 9'
>re.sub(r'^ (((\d+)\.){3})\ d+$', "\g<1>9", "192.168.1.100" ) '192.168.1. 9'
The regular expression changes the last sequence of digits to "9" ("192.168.1.100 " ="192.168.1. 9") but the other code replaces the last digit ("192.168.1.100 " ="192.168.1.109 ").
Mmm - yes, true.
ip = ".".join(ip.spl it('.')[0:3] + ['9'])
As I first stated, in my very particular case, I knew that the last
octet was always going to be a single digit.
But I did learn a lot from everyone else's posts for the more generic
cases. thx! This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics |
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