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How to get a set of keys with largest values?

Hi all,

I have a dictionary with n elements, and I want to get the m(m<=n)
keys with the largest values.

For example, I have dic that includes n=4 elements, I want m=2 keys
have the largest values)
dic = {0:4,3:1,5:2,7:8}
So, the the largest values are [8,4], so the keys are [7,0].

Is there any fast way to implement this algorithm?
Any suggestions are welcome!

Best regards,
Davy

Nov 12 '07 #1
6 6350
On Nov 12, 10:07 am, Davy <zhushe...@gmail.comwrote:
Hi all,

I have a dictionary with n elements, and I want to get the m(m<=n)
keys with the largest values.

For example, I have dic that includes n=4 elements, I want m=2 keys
have the largest values)
dic = {0:4,3:1,5:2,7:8}
So, the the largest values are [8,4], so the keys are [7,0].

Is there any fast way to implement this algorithm?
Any suggestions are welcome!

Best regards,
Davy
Have a look at http://docs.python.org//lib/module-heapq.html

Nov 12 '07 #2
Why are you doing that with key-value pairs? Why not with the array
module or lists?

Nov 12 '07 #3
Jeff <je******@gmail.comwrote:
Why are you doing that with key-value pairs? Why not with the array
module or lists?
The original poster asked about a problem with key-value pairs. I just
answered his question.
Nov 12 '07 #4
On Nov 12, 8:54 pm, Jeff <jeffo...@gmail.comwrote:
Why are you doing that with key-value pairs? Why not with the array
module or lists?
Hi,

The original question is a bit complex. I have to implement a sparse
matrix which use a dict of dict implementation.
For example, sp_mat = {1:{2:1,3:4},2:{4:6,8:9}}.

And I want to get m key with the largest values in each row? Any good
ideas?

Best regards,
Davy

Nov 13 '07 #5
On Nov 12, 1:07 am, Davy <zhushe...@gmail.comwrote:
Hi all,

I have a dictionary with n elements, and I want to get the m(m<=n)
keys with the largest values.

For example, I have dic that includes n=4 elements, I want m=2 keys
have the largest values)
dic = {0:4,3:1,5:2,7:8}
So, the the largest values are [8,4], so the keys are [7,0].

Is there any fast way to implement this algorithm?
Any suggestions are welcome!

Best regards,
Davy
#get a list of tuples, with value in 1st position, key second
li = [(value,key) for key, value in dic.items()]

#sort the list
li.sort()

m = 2
#grab the m highest values, from the end of the list
li_high_keys = [k for v, k in li[-m:]]

p.s. sorry if this ends up appearing multiple times, google groups can
be a bit cranky at times with postings.

Nov 13 '07 #6
On Nov 12, 1:07 am, Davy <zhushe...@gmail.comwrote:
Hi all,

I have a dictionary with n elements, and I want to get the m(m<=n)
keys with the largest values.

For example, I have dic that includes n=4 elements, I want m=2 keys
have the largest values)
dic = {0:4,3:1,5:2,7:8}
So, the the largest values are [8,4], so the keys are [7,0].

Is there any fast way to implement this algorithm?
Any suggestions are welcome!

Best regards,
Davy
#get a list of tuples, with value in 1st position, key second
li = [(value,key) for key, value in dic.items()]

#sort the list
li.sort()

m = 2
#grab the m highest values, from the end of the list
li_high_keys = [k for v, k in li[-m:]]

Nov 13 '07 #7

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