Programming Forums > Script Programming > Python

sixstringartist · Sep 30th, 2007, 3:57 PM

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

(Toggle Plain Text)

>>> int("23")
23
>>> "23" * 2
'2323'
>>> int("23") * 2
46

Arevos · Oct 1st, 2007, 1:26 PM

Some additional useful code:

 python Syntax (Toggle Plain Text) 
>>> 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]
>>> 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

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.

(Toggle Plain Text)

numList = ["12","4","66","55"]
numList.sort(cmp = lambda x,y: int(x) - int(y))
# returns ['4','12','55',66']

Sep 30th, 2007, 3:57 PM	#1
sixstringartist Programmer Join Date: Jun 2005 Posts: 68 Rep Power: 4	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.

Sep 30th, 2007, 4:50 PM	#2
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	(Toggle Plain Text) >>> int("23") 23 >>> "23" * 2 '2323' >>> int("23") * 2 46 >>> int("23") 23 >>> "23" * 2 '2323' >>> int("23") * 2 46 __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Oct 1st, 2007, 1:26 PM	#3
Arevos Programming Guru Join Date: Aug 2005 Location: England Posts: 1,499 Rep Power: 5	Some additional useful code: python Syntax (Toggle Plain Text) >>> 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] >>> 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]

Dec 4th, 2007, 3:27 PM	#5
somehollis Programmer Join Date: May 2006 Location: Memphis, TN Posts: 31 Rep Power: 0	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. (Toggle Plain Text) numList = ["12","4","66","55"] numList.sort(cmp = lambda x,y: int(x) - int(y)) # returns ['4','12','55',66'] numList = ["12","4","66","55"] numList.sort(cmp = lambda x,y: int(x) - int(y)) # returns ['4','12','55',66']

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Oct 5th, 2007, 5:08 PM	#4
sixstringartist Programmer Join Date: Jun 2005 Posts: 68 Rep Power: 4	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.

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Programming Forums > Script Programming > Python

Sorting integer lists