[Python-bugs-list] [ python-Feature Requests-798046 ] select module doesn't allow any iterable.

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Feature Requests item #798046, was opened at 2003-08-31 00:31
Message generated for change (Settings changed) made by bcannon
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>Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Jeremy Fincher (jemfinch)
Assigned to: Nobody/Anonymous (nobody)
Summary: select module doesn't allow any iterable.

Initial Comment:
The select module only allows lists, not any 
iterable.  While this may slightly increase efficiency 
for the select.select() function itself, for many 
applications passing select.select a sets.Set would 
probably be much more efficient (i.e., when things 
are being added/removed from the readable or 
writable lists quite often, the O(n) removal of lists 
would certainly be worse than the O(1) removal of 
sets.) 

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Comment By: Brett Cannon (bcannon)
Date: 2003-09-06 15:22

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There seems to be two things that are preventing the use of an 

object that supports the iterator protocol instead of a list.  One is 

the explicit check that the arguments are lists; PyList_Check is run 

on the passed-in lists for a basic sanity check.  Then there is a call 

to a function called list2set that takes in a Python list and then 

sets the passed-in fd_set properly.  In that function there is 

nothing that screams "we should only use lists" beyond it allows 

assuming a list and thus doesn't have any hoops to jump through.



But the iterator protocol was set up to minimize hoop jumping.  

There seems to be little stopping a move over to using the iterator 

protocol beyond a minimial amount of recoding to rip out the list 

check to replace it with PyIter_Check and instead of using a 'for' 

loop through a list you just use a 'while' calling PyIter_Next .



But since this seems to have gone so long without being changed I 

would feel better about having someone tell me it is okay to 

change.  I will email python-dev and ask.

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Comment By: Armin Rigo (arigo)
Date: 2003-09-02 11:23

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Using select.poll() instead of select.select() might be a

good alternative, at least on platforms that support it, if

the sets are getting large enough for you to want to avoid

having to build lists explicitely as in :



    select.select(list(a), list(b), list(c))



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