Python - Wrong long mantissa in simple calculation

Asked Sep 26 '17 at 04:06

Active Sep 26 '17 at 04:08

Viewed 31 times

So, I new in python and i found a bug in my code. With this combination of variable (a,b,c) result of calculation (d) is wrong (0.8999999999999 instead 0.9). Other combination of variable calculate correct. I use python 3.6. What have I missed?

a = 0.3
b = 2
c = 0.6

d = a + (b - 1)*c
print(d)

edited Sep 26 '17 at 04:08

asked Sep 26 '17 at 04:06

Vadim

2

That your program is correct and floating point number arithmetic isn't exact. – Alex Huszagh Sep 26 '17 at 04:07
you can use round of >> round(d,2) – Somil Sep 26 '17 at 04:10
You can try to round your result, but code is correct – amarynets Sep 26 '17 at 04:10
Can I use something other than rounding in my situation? – Vadim Sep 26 '17 at 04:11
go through with docs https://docs.python.org/2/tutorial/floatingpoint.html – Somil Sep 26 '17 at 04:13
Also see [The Floating Point Guide](http://floating-point-gui.de/) – Davy M Sep 26 '17 at 04:13
Many thanks, i will try – Vadim Sep 26 '17 at 04:15

Python - Wrong long mantissa in simple calculation

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