On 20/11/2021 09.17, Chris Angelico wrote: > On Sat, Nov 20, 2021 at 5:08 AM ast <ast@invalid> wrote: >> Le 19/11/2021 à 03:51, MRAB a écrit : >>> On 2021-11-19 02:40, 2qdxy4rzwzuui...@potatochowder.com wrote: >>>> On 2021-11-18 at 23:16:32 -0300, >>>> René Silva Valdés <rene.silva.val...@gmail.com> wrote: >>>>> Working with floats i noticed that: >>>>> int(23.99999999999999/12) returns 1, and >>>>> int(23.999999999999999/12) returns 2
Has the OP (now) realised that the observation is a "feature" not a "bug"? It is one of the difficulties of representing small numbers or numerical-components in binary - there are many decimal values which cannot be accurately-expressed in binary - exactly as noted. ... >> >>> 0.3 + 0.3 + 0.3 == 0.9 >> False > > That's because 0.3 is not 3/10. It's not because floats are > "unreliable" or "inaccurate". It's because the ones you're entering > are not what you think they are. > > When will people understand this? > (Probably never. Sigh.) Am not aware of any institution which teaches the inner-workings of a CPU/ALU/FPU/GPU in a general programming class, ie "Programming" and particularly "Coding", have diverged from "Computer Science" - in at least this respect. As well as the approximations involved in trying to maintain decimal-numbers (floats/floating-point numbers), and particularly values to the 'right' of a decimal-point; we had to study?suffer classes in "Numerical Analysis" and be able to gauge the declining accuracy and precision of sundry calculations. A skill disappearing as fast as slide-rules!? This 'pool of ignorance' is particularly noticeable in folk who have come 'up' through the 'CodeCamp'/'BootCamp' approach to training. On the other hand, if one is not intending to 'get into' a scientific or highly mathematical branch of computing/Python, eg commercial applications using (only) Decimal (or int), the average web-app, and similar; why bother? -- Regards, =dn -- https://mail.python.org/mailman/listinfo/python-list
