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Python

Posted by chrisp
chrisp
13,686 Points

For the regular expression grouping construct, why is 'one' outputted and not 'zero'?

Not sure how the expression works and not getting the outputting process. 

 x = re.search('(?<=-)\w+', 'zero-one')
 m.group(0)
'one'

1 Answer

karis hutcheson
karis hutcheson
7,036 Points

This is because the expression 

?<=  # *something*

is a special "look-behind" character in Python regex. Meaning it's going to take whatever you put in something and look after it for the expression following. 

 (?<=-)\w+

looks for \w+ that occurs after a hyphen.

more information here: Python RegEx

chrisp
chrisp
13,686 Points

Thanks for the explanation, link, and examples. Now that looking through it again, it now makes sense, thanks you Karis. Just been 2 days I started with Python, so far it's pretty sweet!

All the best to you and your CS journey!

karis hutcheson
karis hutcheson
7,036 Points

No prob! :) and thank you.