Most efficient solution?

Simon Brunning SBrunning at trisystems.co.uk
Mon Jul 16 16:41:21 CEST 2001


> From:	Simon Brunning 
> 	From:	Jeffery D. Collins [SMTP:jcollins at boulder.net]
> 	> List B consists of my "stopwords", meaning, the words I don't want
> included in my final version of list A. So what I need to 
> 	> do is check every item in list A, and if it occurs in list B, then
> I want to remove it from the final version of A. My first thought 
> 	> would be:
> 	> 
> 	> for eachItem in A:
> 	>     if eachItem in B:
> 	>         A.remove(eachItem)
> 	> 
> 
> 	How about: 
> 
> 	map(A.remove, B)
>  
> Clever! Unfortunately, it dies (giving a ValueError) if any of the tokens
> in B are not present in A. Nasty, but how about:
> 
> map((A + B).remove, B)
 
That will teach me to post without testing. This doesn't work at all - items
from B are removed from the temporary, unnamed list created for A + B.

A bit neared the truth would be:

A += B
map(A.remove, B)

But this doesn't really work, either. Only the first occurrence of each
token in B is removed.

It strikes me that if B is large, it might be quicker to build a re pattern
from its elements, and match on that, rather than use 'in'. I'll give that a
bash later.

Cheers,
Simon Brunning
TriSystems Ltd.
sbrunning at trisystems.co.uk




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