Unexpected decimal on a subtraction

Question

I'm using Python 3.5. I have a basic operation but I get a wrong result:

def main(argv):
    cms=None
    damin=4.815
    dbmax=4.858
    it=(dbmax-damin)*1000
    print('Damin {0}    Dbmax {1}    IT {2}'.format(damin, dbmax, dbmax-damin))

So the result is:

Damin 4.815    Dbmax 4.858    IT 0.04299999999999926

But I expect this :

Damin 4.815    Dbmax 4.858    IT 0.043

https://docs.python.org/3/tutorial/floatingpoint.html – Tim Bender Sep 29 '15 at 07:17 — Tim Bender, Sep 29 '15 at 07:17

score 0 · Answer 1 · answered Sep 29 '15 at 07:19

0

Reading up on floating point numbers may be worth while: https://docs.python.org/3/tutorial/floatingpoint.html

Not every number can be represented quite so perfectly and programs do there best to use the closest representation possible. Including when interpreting the magic numbers written into the code.

answered Sep 29 '15 at 07:19

Tim Bender

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Tip: `decimal` module can get the most close float number. – Remi Guan Sep 29 '15 at 07:21

Unexpected decimal on a subtraction

1 Answers1