Programming Forums - Sorting integer lists

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sixstringartist

Sep 30th, 2007 3:57 PM

Sorting integer lists

Im studying python and I am unsure of how to solve a problem.

Im taking user input of two strings consisting of integers. I split these on whitespace into two lists, merge the lists, and sort it. My problem is that these lists are being sorted by character and not integers (i.e. 22 > 3).

Ive searched for a solution to this but have yet to find one. Does Python know these are characters? Can I convert each value, element-by-element into integers and expect it to sort them numerically?

Thanks.

DaWei

Sep 30th, 2007 4:50 PM

>>> int("23")

23

>>> "23" * 2

'2323'

>>> int("23") * 2

46

Arevos

Oct 1st, 2007 1:26 PM

Some additional useful code:

>>> xs = ["2", "13", "3"]
>>> xs.sort()
>>> xs
['13', '2', '3']
 
>>> ys = map(int, xs)
>>> ys
[13, 2, 3]
>>> ys.sort()
>>> ys
[2, 3, 13]
 
>>> zs = [int(i) for i in x]
>>> zs
[13, 2, 3]
>>> zs.sort()
[2, 3, 13]

sixstringartist

Oct 5th, 2007 5:08 PM

Thanks DaWei but I was already aware that the issue was with they type of data in the list. What I was looking for was an approach like Arevos posted. I resorted to converting each value one by one to an int, but I was looking for a built-in way. It seems "map()" is what I was looking for. I'll read more about it.

somehollis

Dec 4th, 2007 3:27 PM

Re: Sorting integer lists

I realize this thread is rather old, but for reference, you can also use your list's sort() method if you add a parameter to it.

numList = ["12","4","66","55"]

numList.sort(cmp = lambda x,y: int(x) - int(y))

# returns ['4','12','55',66']

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