123.4+2=125.40000000000001

[Konrad Hinsen]

Peter Koppatz <pkop at brb.midat.de> writes:

> >>> 123.4+2
> 125.40000000000001   # is this OK?
> >>> print 123.4+2
> 125.4
> >>>
> 
> On my calculator: 123.4+2 = 125.4 !?

Because your calculator works with a decimal representation of
numbers, whereas Python (and the vast majority of other programming
languages) uses a binary representation. In binary, the result of your
calculation has an infinite number of digits (like 1./3. has in
decimal) and cannot be represented exactly in a computer. That causes
the effect you observe.
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