How would I change....
"Take dog1 and dog5 to the dog kennel"
to
"Take animal_1 and animal_5 to the dog kennel"
? So I only want to substitute "animal_" for "dog" if "dog" has a number after it. Any help is welcome.
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1Did you try doing some research? The simplest way would be to match the digit and put it back in the replacement. Another way would be to use a lookahead.Jerry– Jerry2014-08-26 16:22:19 +00:00Commented Aug 26, 2014 at 16:22
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I've read the python doc on regex, the tutorialspoint doc as well as these message boards. I've been playing around with my interpreter with no luck. I could do it with ordinary python but I figured there would be a short way with regex.user3319934– user33199342014-08-26 16:39:15 +00:00Commented Aug 26, 2014 at 16:39
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I gave you two hints with that comment. Did you make use of them? The lookahead itself takes a while to be understood usually.Jerry– Jerry2014-08-26 16:41:42 +00:00Commented Aug 26, 2014 at 16:41
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I got my answer from a quick read of the python regex functions. But mine below is also the most basic.user2615862– user26158622014-08-26 16:45:42 +00:00Commented Aug 26, 2014 at 16:45
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@Jerry I said thats how I found my solution (answered below). I think you mean the guy who asked the question (user3319934)user2615862– user26158622014-08-26 17:24:46 +00:00Commented Aug 26, 2014 at 17:24
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3 Answers
You could try the below re.sub function,
>>> import re
>>> s = "Take dog1 and dog5 to the dog kennel"
>>> m = re.sub(r'dog(\d)', r'animal_\1', s)
>>> m
'Take animal_1 and animal_5 to the dog kennel'
Through lookahead,
>>> m = re.sub(r'dog(?=\d)', r'animal_', s)
>>> m
'Take animal_1 and animal_5 to the dog kennel'
2 Comments
user3319934
Ah! This is what I was looking for. It works. I couldn't find out how to reference the parameter. "\1" did the trick.
user3319934
Thanks again. I'm a noob here.
you can probably do the following:
import re
old_sting = 'Take dog1 and dog5 to the dog kennel'
dog_finder = re.compile(r'dog(\d+)')
new_string = re.sub(dog_finder, lambda dog: 'animal_' + dog.group(1), old_sting)
Comments
Something like this:
>>> import re
>>> def dog_replace(matchobj):
... number = matchobj.group(0)[-1:];
... return "animal_"+ number
>>> re.sub('dog[0-9]', dog_replace, "Take dog1 and dog5 to the dog kennel")
"Take animal_1 and animal_5 to the dog kennel"
This works as I have tested it on my local machine. It is essentially the same as the lambda...i'm just an old bear and I think this is more readable.
