Feature Requests item #1281053, was opened at 2005-09-02 18:30
Message generated for change (Comment added) made by rhettinger
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Category: Python Library
Group: None
Status: Closed
Resolution: Invalid
Priority: 5
Submitted By: Ecnassianer of the Green Storm (ecnassianer)
Assigned to: Nobody/Anonymous (nobody)
Summary: non-sequence map() arguments for optimization
Initial Comment:
I'm trying to optimize some code thats similiar to this:
anObject = someConstructor() # This isn't a sequence
myList = myListMaker() # This IS a sequence
for items in myList:
function(items, anObject)
I'd like to be able to do this:
map(function, myList, anObject)
But the map function takes two lists, so I have to do
somethign like this:
list2 = []
for x in range(len(myList)):
list2.append(anObject)
map(function, myList, list2)
But intializing list2 kind of defeats the purpose of
optimization. I was looking for some way to convince
anObject that it was really a list containing a lots of
entries of itself, but couldn't find anything in the API.
What I'd love to have is a version of the map function
which takes a function, a sequence, and an object as
arguments and calls the function with the first
argument as an element in the sequence, and the second
element as the object for as many times as their are
items in the sequence.
(Note: Currently the API says if you pass sequences of
unequal lenghths to map, it uses None to fill up the
rest of the calls)
----------------------------------------------------------------------
>Comment By: Raymond Hettinger (rhettinger)
Date: 2005-09-03 11:36
Message:
Logged In: YES
user_id=80475
Or just:
map(function, myList, repeat(anObject, len(myList)))
----------------------------------------------------------------------
Comment By: Raymond Hettinger (rhettinger)
Date: 2005-09-03 11:26
Message:
Logged In: YES
user_id=80475
from itertools import imap, repeat
list(imap(function, myList, repeat(anObject)))
----------------------------------------------------------------------
Comment By: Reinhold Birkenfeld (birkenfeld)
Date: 2005-09-03 01:43
Message:
Logged In: YES
user_id=1188172
Use a list comprehension:
[function(item, anObject) for item in myList]
or, if you must use map,
map(lambda item: function(item, anObject), myList)
And please direct such questions to comp.lang.python in the
future.
----------------------------------------------------------------------
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