On Tue, 6 Sep 2011 03:57 pm xyz wrote: > hi all: > > As we know , 1.1 * 1.1 is 1.21 . > But in python ,I got following : > >>>> 1.1 * 1.1 > 1.2100000000000002
The problem is that 1.1 is a *decimal* number, but computers use *binary*, and it is impossible to express 1.1 exactly as a binary number. So when you type 1.1 into nearly all computer languages, what you are actually getting is a tiny bit more than 1.1: >>> repr(1.1) '1.1000000000000001' which is the closest number to 1.1 that is possible using a C double floating point number. Normally you don't see it, because Python truncates the result when printing: >>> str(1.1) '1.1' but the difference is there. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
