any modules having a function to partition a list by predicate provided?
knifenomad
just by implementing simple function like below.
def partition(target, predicate):
"""
split a list into two partitions with a predicate
provided.
any better ideas? :)
"""
true = []
false= []
for item in target:
if predicates(item):
true.append(item)
else:
false.append(item)
return true, false
but i wonder if there's another way to do this with standard libraries
or .. built-ins.
if it's not, i'd like the list objects to have partition method like
string module has.
true, false = [1,2,3,4].partition(lambda x: x >1)
print true, false
[2,3,4] [1]
Chris Rebert
> i know it's not very hard to get that solution.
> just by implementing simple function like below.
>
> def partition(target, predicate):
> """
> split a list into two partitions with a predicate
> provided.
> any better ideas? :)
> """
> true = []
> false= []
> for item in target:
> if predicates(item):
> true.append(item)
> else:
> false.append(item)
> return true, false
>
> but i wonder if there's another way to do this with standard libraries
> or .. built-ins.
> if it's not, i'd like the list objects to have partition method like
> string module has.
(A) str.partition() has a /completely/ different meaning from your partition()
(B) You'd probably have better luck getting it added to the itertools
module since the concept is applicable to all iterables.
[http://docs.python.org/library/itertools.html]
Cheers,
Chris
--
http://blog.rebertia.com
segunai
yep, my mistake. i shouldn't have compared it to string's partition().
i just wanted that convenience string.partition() has as a built-in.
anyway, thanks for itertools. :)
Krister Svanlund
> http://mail.python.org/mailman/listinfo/python-list
>
The way I would do it is probably apply filter to the list:
>>> def f(x): return x % 2 != 0 and x % 3 != 0
...
>>> filter(f, range(2, 25))
[5, 7, 11, 13, 17, 19, 23]
Bryan
> i know it's not very hard to get that solution.
> just by implementing simple function like below.
>
> def partition(target, predicate):
> """
> split a list into two partitions with a predicate
> provided.
> any better ideas? :)
> """
> true = []
> false= []
> for item in target:
> if predicates(item):
> true.append(item)
> else:
> false.append(item)
> return true, false
>
> but i wonder if there's another way to do this with standard libraries
> or .. built-ins.
> if it's not, i'd like the list objects to have partition method
I've oft collected partitions in a dict, so I'll suggest the
generalization:
def partition(target, predicate):
result = {}
for item in target:
result.setdefault(predicate(item), []).append(item)
return result
> true, false = [1,2,3,4].partition(lambda x: x >1)
>
> print true, false
> [2,3,4] [1]
With my version you'd get:
{False: [1], True: [2, 3, 4]}
--
--Bryan