[Python-Dev] Examples for PEP 572
tjreedy at udel.edu
Thu Jul 5 01:13:13 EDT 2018
On 7/4/2018 2:32 PM, Sven R. Kunze wrote:
> Sorry for adding yet another mail. :-(
> On 04.07.2018 10:54, Serhiy Storchaka wrote:
>> Sorry, this PEP was rewritten so many times that I missed your Appendix.
>>> while total != (total := total + term):
>>> term *= mx2 / (i*(i+1))
>>> i += 2
>>> return total
> This very example here caught my eye.
> Isn't total not always equal to total
Repeat response given elsewhere. No. Python has limited precision
floats, not reals. Floats do not obey laws of real numbers.
>>> 1e50 + 1e34 == 1e50
>>> 1e50 + 1e35 == 1e50
Basic numerical analysis operation: approximate infinite sum of
decreasing terms by summing terms until they become small enough that
they can be ignored.
Terry Jan Reedy
More information about the Python-Dev