Not rounding to desired decimal places?

[Gribouillis]

Floating numbers are stored in binary format by the computer. Real numbers such as 0.1 that have a finite number of decimal digits may have an infinite number of binary digits. It means that they are not stored exactly and a rounding error may become visible in arithmetic operations. For example

>>> 0.10047 - (0.09047 + 0.01)
1.3877787807814457e-17
>>> 0.09047 * 100
9.046999999999999

See this manual page. Note that this limitation is not due to the Python language.