Floating point weirdness

[Joshua Ginsberg]

WTF, mate?
'2.3.3 (#1, May 7 2004, 10:31:40) \n[GCC 3.3.3 20040412 (Red Hat Linux
3.3.3-7)]'19.899999999999999

Why can't I just get 19.95?

-jag

 

[Benjamin Niemann]

WTF, mate?


'2.3.3 (#1, May 7 2004, 10:31:40) \n[GCC 3.3.3 20040412 (Red Hat Linux
3.3.3-7)]'

19.949999999999999

19.949999999999999

19.899999999999999

Why can't I just get 19.95?

floats are represented as 64 (or 128?) bit values and there's no value
that exactly represents 19.95 or 19.9 (=round(19.949, 1)). The last
example results in the closest value to 19.9, but not exactly. Python
prints this value with maximum precision. If you want a string
representation of a float with e.g. 2 digits precision, use
"%.2f" % 19.949