On Sat, 2009-03-21 at 04:12 +0100, Lada Kugis wrote: > I'm a newbie learning python, so forgive for, what may seem to some, > like a stupid question. > > I understand the basic integer and fp type, but what I'm having a > little trouble are the long type and infinite precision type. > > Also, when I do > > >>> math.pi - (math.sqrt(math.pi))**2. > > I get > > >>>4.4408920985006262e-016 > > Please, could someone in just a few words, in newbie speak, explain > why does that happen ? And what do the types actually mean ? What I > mean, how can something have infinite precision but still not return > zero as a result. (Btw, I always thought floating points had precision > up to 8 significant digits, doubles 16). > > Nice regards > Lada
The types used here are 'float'. >>> math.pi 3.1415926535897931 >>> type(math.pi) <type 'float'> Floating point is inherently imprecise. Whatever encoding is used to represent the number will have a finite size. That finite size puts a limit on the precision available. >>> 1.0/3 0.33333333333333331 >>> type(1.0/3) <type 'float'> Do you see how small a number the result represents >>> print "%2.32f" % (4.4408920985006262e-016) 0.00000000000000044408920985006262 Have you tried this in any other programming languages? -- http://mail.python.org/mailman/listinfo/python-list
