Adding Decimals to classes with OOP + rounding to significant digits (ATM demo)

[bowlofred]

The round context isn't used here because you've passed in a float initially. That float doesn't represent exactly what you want and is already higher than the target. If you want to be exact, you have to pass in a string and let Decimal do the conversion.

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>>> Decimal(.505) #.505 isn't exact Decimal('0.50500000000000000444089209850062616169452667236328125') #Not "5.05".  Is closer to 5.1 >>> round(Decimal(.505),2) Decimal('0.51')   # Instead of float, pass in a string. '.505' is exact. >>> Decimal('.505') Decimal('0.505') >>> round(Decimal('.505'),2) # now the context matters Decimal('0.50') >>> decimal.getcontext().rounding = decimal.ROUND_HALF_UP >>> round(Decimal('.505'),2) Decimal('0.51')