Python random formatting issues

[Gribouillis]

This is a limitation of binary floating point arithmetics. The python number 0.0952 is not exactly equal to the real number 952/10000 because 0.0952 is stored in base 2 and only a finite number of bits are kept. In other words it cannot be represented exactly in memory at the machine precision. You can see the error with the fractions module

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>>> from fractions import Fraction >>> Fraction(0.0952) - Fraction(952, 10000) Fraction(77, 11258999068426240000)

you see that there is an error. This is not a Python specific error: you would get the same behavior in all languages or systems that use 64 bits floating point numbers.

The consequence for you is that B*100 is not exactly equal to 9.52

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>>> x = 0.0952 >>> x * 100 9.520000000000001

By printing with the format() method, you don't see this error because the format method performs a rounding when transforming the number to a string

1 2	>>> '{:.2f}'.format(x * 100) '9.52'