python regex and replace

Question

I am trying to learn python and regex at the same time and I am having some trouble in finding how to match till end of string and make a replacement on the fly.

So, I have a string like so:

ss="this_is_my_awesome_string/mysuperid=687y98jhAlsji"

What I'd want is to first find 687y98jhAlsji (I do not know this content before hand) and then replace it to myreplacedstuff like so:

ss="this_is_my_awesome_string/mysuperid=myreplacedstuff"

Ideally, I'd want to do a regex and replace by first finding the contents after mysuperid= (till the end of string) and then perform a .replace or .sub if this makes sense.

I would appreciate any guidance on this.

Casimir et Hippolyte · Accepted Answer · 2013-06-10 01:28:31Z

6

You can try this:

 re.sub(r'[^=]+$', 'myreplacedstuff', ss)

The idea is to use a character class that exclude the delimiter (here =) and to anchor the pattern with $

explanation:

[^=] is a character class and means all characters that are not =
[^=]+ one or more characters from this class
$ end of the string

Since the regex engine works from the left to the right, only characters that are not an = at the end of the string are matched.

edited Jun 10, 2013 at 1:28

answered Jun 10, 2013 at 0:15

Casimir et Hippolyte

90k5 gold badges102 silver badges131 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

AJW Over a year ago

Thanks so much for this. So, does the +$ look for end of string?

Casimir et Hippolyte Over a year ago

No only $, + is quantifier for [^=] that mean 1 or more times, I will edit a more detailed explanation soon.

AJW Over a year ago

Thanks so much for your detailed explanation - I have certainly learnt here. Accepted your answer.

TerryA · Accepted Answer · 2013-06-10 00:17:03Z

1

You can use regular expressions:

>>> import re
>>> mymatch = re.search(r'mysuperid=(.*)', ss)
>>> ss.replace(mymatch.group(1), 'replacing_stuff')
'this_is_my_awesome_string/mysuperid=replacing_stuff'

You should probably use @Casimir's answer though. It looks cleaner, and I'm not that good at regex :p.

answered Jun 10, 2013 at 0:17

TerryA

60.2k11 gold badges122 silver badges148 bronze badges

3 Comments

AJW Over a year ago

thanks so much for the alternative solution. I agree, Casimirs answer is a clean one liner. I agree - I am trying to be good with regex! I am quite bad at this!

TerryA Over a year ago

@JamesW Well, you aren't alone :)

zmo Over a year ago

you should read more about regexps on sites like courses on the MIT and also practice on tutorial sites. I think it helps a lot to understand that Regexps are "simply" automata with cabalistical characters. In the end, it's expression is far less sophisticated than most programming language.. but the paradox is that it is harder to learn :-)

Collectives™ on Stack Overflow

python regex and replace

2 Answers 2

3 Comments

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related