Re: function to split strings and lists on predicate
On Mon, 06 Jan 2014 06:48:11 +, Mark Lawrence wrote: I came across this over the weekend http://paddy3118.blogspot.co.uk/2013/10/unifying-pythons-string-and-lis t.html. I couldn't come up with a solution to the fsplit function that seemed in any way cleaner. What can our nest of avid Pythonistas come up with? Looks like that link is already broken. Try the first half of page: http://paddy3118.blogspot.co.uk/2013_10_01_archive.html I can't see any way to simplify the generator Paddy produced, but the thing that bothered me is that it won't work on iterables, such as itself. For thar reason I think I'd stick with the separate functions, or write an adaptor to convert a iterable of lists to one of strings. -- DaveA -- https://mail.python.org/mailman/listinfo/python-list
function to split strings and lists on predicate
I came across this over the weekend http://paddy3118.blogspot.co.uk/2013/10/unifying-pythons-string-and-list.html. I couldn't come up with a solution to the fsplit function that seemed in any way cleaner. What can our nest of avid Pythonistas come up with? -- My fellow Pythonistas, ask not what our language can do for you, ask what you can do for our language. Mark Lawrence -- https://mail.python.org/mailman/listinfo/python-list
Re: Strings and Lists
Thank you all very much for your responses. It's especially reassuring to hear about other Python GA's as I have had some scepticism about Python's speed (or lack of it) being too big a problem for such an application. With regard to using numeric, arrays or integer lists -- I didn't mention that these strings can also contain wild cards (so I suppose it's not really binary -- sorry). This is traditionally done using a '#' symbol, but I was imagining using a value of None in a boolean list to represent this. Also there is currently a fair bit of research going into other representations (floating-point values, paired values etc) so I was hoping to be able to keep my framework extensible for the future. Many thanks again for your help. I will ``take the plunge'' and give the boolean list a go I think! -- http://mail.python.org/mailman/listinfo/python-list
Re: Strings and Lists
In article <[EMAIL PROTECTED]>,
[EMAIL PROTECTED] (Tom Longridge) wrote:
> My current Python project involves lots repeatating code blocks,
> mainly centred around a binary string of data. It's a genetic
> algorithm in which there are lots of strings (the chromosomes) which
> get mixed, mutated and compared a lot.
>
> Given Python's great list processing abilities and the relative
> inefficiencies some string operations, I was considering using a list
> of True and False values rather than a binary string.
>
> I somehow doubt there would be a clear-cut answer to this, but from
> this description, does anyone have any reason to think that one way
> would be much more efficient than the other? (I realise the best way
> would be to do both and `timeit` to see which is faster, but it's a
> sizeable program and if anybody considers it a no-brainer I'd much
> rather know now!)
I make no representations about how much mileage you would
get out of it, but if character data suits your purposes and
you just need a mutable array - in principle, I think it would
be more efficient to use an array. Like,
import array
a = array.array('c', strdata)
As I understand it, this object simply contains character data,
not a list of 1 character string objects, so it's much more
economical to store and examine.
Donn Cave, [EMAIL PROTECTED]
--
http://mail.python.org/mailman/listinfo/python-list
Re: Strings and Lists
Tom Longridge wrote: My current Python project involves lots repeatating code blocks, mainly centred around a binary string of data. It's a genetic algorithm in which there are lots of strings (the chromosomes) which get mixed, mutated and compared a lot. Given Python's great list processing abilities and the relative inefficiencies some string operations, I was considering using a list of True and False values rather than a binary string. I somehow doubt there would be a clear-cut answer to this, but from this description, does anyone have any reason to think that one way would be much more efficient than the other? (I realise the best way would be to do both and `timeit` to see which is faster, but it's a sizeable program and if anybody considers it a no-brainer I'd much rather know now!) Any advice would be gladly recieved. It depends more on the operations you are performing, and more importantly *which of those you have measured and found to be slow*, than on anything else. If, for example, you've got a particular complex set of slicing, dicing, and mutating operations going on, then that might say use one type of data structure. If, on the other hand, the evaluation of the fitness function is what is taking most of the time, then you should focus on what that algorithm does and needs and, after profiling (to get real data rather than shots-in-the-dark), you can pick an appropriate data structure for optimizing those operations. Strings seem to be what people pick, by default, without much thought, but I doubt they're the right thing for the majority of GA work... -Peter -- http://mail.python.org/mailman/listinfo/python-list
Re: Strings and Lists
On 18 Apr 2005 04:42:17 -0700, Tom Longridge <[EMAIL PROTECTED]> wrote: > My current Python project involves lots repeatating code blocks, > mainly centred around a binary string of data. It's a genetic > algorithm in which there are lots of strings (the chromosomes) which > get mixed, mutated and compared a lot. > > Given Python's great list processing abilities and the relative > inefficiencies some string operations, I was considering using a list > of True and False values rather than a binary string. > > I somehow doubt there would be a clear-cut answer to this, but from > this description, does anyone have any reason to think that one way > would be much more efficient than the other? (I realise the best way > would be to do both and `timeit` to see which is faster, but it's a > sizeable program and if anybody considers it a no-brainer I'd much > rather know now!) > > Any advice would be gladly recieved. > -- > http://mail.python.org/mailman/listinfo/python-list > Tom, it seems to me that, if efficiency is your main goal, you should store your data as a list of integers, and use the bit-twiddling operators to get at your data. These should be *very* fast, as well as memory efficient. Peace Bill Mill bill.mill at gmail.com -- http://mail.python.org/mailman/listinfo/python-list
Re: Strings and Lists
Hi, I not sure what sorts of operations you plan to do. But if you intend to use fixed length arrays or even carrying out repetetive operations. You should probably look at numeric http://numeric.scipy.org/ On 18 Apr 2005 04:42:17 -0700, Tom Longridge <[EMAIL PROTECTED]> wrote: > My current Python project involves lots repeatating code blocks, > mainly centred around a binary string of data. It's a genetic > algorithm in which there are lots of strings (the chromosomes) which > get mixed, mutated and compared a lot. > > Given Python's great list processing abilities and the relative > inefficiencies some string operations, I was considering using a list > of True and False values rather than a binary string. > > I somehow doubt there would be a clear-cut answer to this, but from > this description, does anyone have any reason to think that one way > would be much more efficient than the other? (I realise the best way > would be to do both and `timeit` to see which is faster, but it's a > sizeable program and if anybody considers it a no-brainer I'd much > rather know now!) > > Any advice would be gladly recieved. > -- > http://mail.python.org/mailman/listinfo/python-list > -- http://blogs.applibase.net/sidharth -- http://mail.python.org/mailman/listinfo/python-list
Re: Strings and Lists
Hello Tom, I think it is more efficient if we can use list (with True,False) member to do genetics algorithms. Of course a lot of works to do to change from string binary into boolean list. I do programming genetics algorithms in C# I guess I have to modify my program also because my old program use binary string manipulation. Sincerely Yours, Pujo -- http://mail.python.org/mailman/listinfo/python-list
Strings and Lists
My current Python project involves lots repeatating code blocks, mainly centred around a binary string of data. It's a genetic algorithm in which there are lots of strings (the chromosomes) which get mixed, mutated and compared a lot. Given Python's great list processing abilities and the relative inefficiencies some string operations, I was considering using a list of True and False values rather than a binary string. I somehow doubt there would be a clear-cut answer to this, but from this description, does anyone have any reason to think that one way would be much more efficient than the other? (I realise the best way would be to do both and `timeit` to see which is faster, but it's a sizeable program and if anybody considers it a no-brainer I'd much rather know now!) Any advice would be gladly recieved. -- http://mail.python.org/mailman/listinfo/python-list
