On Aug 12, 9:43 pm, Bradley Hintze <bradle...@aggiemail.usu.edu> wrote: > Hi all. > > Is there a way I can keep my floating point number as I typed it? For > example, I want 34.52 to be 34.52 and NOT 34.5200000002.
Nitpick: unless you're on very unusual hardware, you're missing some zeros here. On my machine, under Python 2.6, the float 34.52 displays as 34.520000000000003, and the value stored internally is actually 34.52000000000000312638803734444081783294677734375; so that's within 1 part in 10**16 of the value you entered. Why do you care? That's a serious question, and its answer goes a long way to determining what you should do. - If you're doing calculations with this number, then the difference between the number Python stores and 34.52 is so miniscule that in normal situations it's not going to matter. In particular, if it represents some physical quantity then any error in the representation will be swamped by the inherent measurement error. IOW, it's not worth worrying about. - If you're printing this number, and you just want the output to look nice (why? perhaps because you're showing this to other people?), then use float formatting operations to limit the number of decimal places you're printing. For example, '%.6f' % my_float, or format(my_float, '.6f'), will give my_float to 6 places after the decimal point. Or, as others have mentioned, it just so happens that Python 2.7 and 3.x will output a nice representation for this float automatically. That wouldn't necessarily be true if the result were coming from a calculation, though, so you shouldn't rely on repr producing nice results in those versions of Python. - If you *really* need a number that represents the *exact* value 34.52, then use the decimal module, or perhaps consider using a simple home-brewed fixed-point representation. One situation where you might care is when doing financial calculations, and in particular when rounding a quantity to a smaller number of decimal digits. Here binary floats can give unpredictable results in halfway cases. (E.g., round(2.675, 2) might give 2.68 or 2.67, depending on what version of Python you're using, and also possibly depending on your platforms.) -- Mark -- http://mail.python.org/mailman/listinfo/python-list
