On Dec 14, 5:27 pm, Steven D'Aprano <steve +comp.lang.pyt...@pearwood.info> wrote: > On Wed, 14 Dec 2011 14:20:40 -0800, Eric wrote: > > I'm trying to read some file data into a set of arrays. The file data > > is just four columns of numbers, like so: > > > 1.2 2.2 3.3 0.5 > > 0.1 0.2 1.0 10.1 > > ... and so on > > > I'd like to read this into four arrays, one array for each column. > > Alternatively, I guess something like this is okay too: > > > [[1.2, 2.2, 3.3, 0.5], [0.1, 0.2, 1.0, 10.1], ... and so on] > > First thing: due to the fundamental nature of binary floating point > numbers, if you convert text like "0.1" to a float, you don't get 0.1, > you get 0.10000000000000001. That is because 0.1000...01 is the closest > possible combination of fractions of 1/2, 1/4, 1/8, ... that adds up to > 1/10. > > If this fact disturbs you, you can import the decimal module and use > decimal.Decimal instead; otherwise forget I said anything and continue > using float. I will assume you're happy with floats. >
Yeah, I don't think it'll be a problem. As I understand it a float in python is a double in C and all our old C programs used doubles. From PDP-11 to MIPS3k to P2 I've seen what I think may have been rounding or precision errors but I haven't heard any complaints because of them. Thanks, eric -- http://mail.python.org/mailman/listinfo/python-list
