Cameron Walsh wrote:
> Hi,
>> I have two lists, A and B, such that B is a subset of A.
>> I wish to sort A such that the elements in B are at the beginning of A,
> and keep the existing order otherwise, i.e. stable sort. The order of
> elements in B will always be correct.
>> for example:
>> A = [0,1,2,3,4,5,6,7,8,9,10]
> B = [2,3,7,8]
>> desired_result = [2,3,7,8,0,1,4,5,6,9,10]
>>> At the moment I have defined a comparator function:
>> def sort_by_in_list(x,y):
> ret = 0
> if x in B:
> ret -= 1
> if y in B:
> ret += 1
> return ret
>> and am using:
>> A.sort(sort_by_in_list)
>> which does produce the desired results.
>> I do now have a few questions:
>> 1.) Is this the most efficient method for up to around 500 elements? If
> not, what would be better?
> 2.) This current version does not allow me to choose a different list
> for B. Is there a bind_third function of some description that I could
> use to define a new function with 3 parameters, feed it the third (the
> list to sort by), and have the A.sort(sort_by_in_list) provide the other
> 2 variables?
>>> Regards to all,
>> Cameron.
Well I found an answer to the second question with the following:
>>> A=[0,1,2,3,4,5,6,7,8,9,10]
>>> B=[2,3,7,8]
>>> def sort_by_in_list(in_list):
def ret_function(x,y):
ret = 0
if x in in_list:
ret -= 1
if y in in_list:
ret += 1
return ret
return ret_function
>>> A.sort(sort_by_in_list(B))
>>> A
[2, 3, 7, 8, 0, 1, 4, 5, 6, 9, 10]
Hope it helps someone,
Cameron.
