I am trying to use the Decimal module to do some FX calculations (instead of using floats).
However when I do the following, I do not get the expected value output:
>>> from decimal import Decimal
>>> x = Decimal(1.3755)
>>> y = Decimal(1.2627)
>>> z = y/(1/x)
>>> print(z)
1.736843849999999839084452447
>>>
The output should be: 1.73684385
I thought using Decimals would correct this issue. How can I resolve this rounding issue?
from decimal import Decimal
x = Decimal('1.3755')
y = Decimal('1.2627')
print(y/(1/x))
# 1.736843850000000000000000000
Use str to construct Decimal instead of real number.
x = Decimal('5.73') and y = Decimal('6.7'), then print(y/(1/x)) gives 38.39099999999999999999999999 rather than the expected 38.39100000000000000000000000.String decimal objects are required:
>>> from decimal import Decimal
>>> x = Decimal('1.3755')
>>> y = Decimal('1.2627')
>>> z = y/(1/x)
>>> print(z)
1.736843850000000000000000000
>>>
Otherwise they would still be treated as regular python floats.
As @schwobaseggl mentioned:
Note that the float is passed to the Decimal constructor, so the precision is lost there already. The Decimal constructor has no chance of knowing the desired precision. The result is still a decimal object, but with the precision of the passed float.
you can use 0:.nf to round the numbers like below
:
print(z)
# 1.736843849999999839084452447
print("{0:.8f}".format(z))
# 1.73684385
Decimal objects who when handled with intent deal with the precision themselves. This question is not about string formatting.
try this, this will helps you, set your precision level
>>> from decimal import *
>>> getcontext().prec = 6
>>> Decimal(1) / Decimal(7)
Decimal('0.142857')
>>> getcontext().prec = 28
>>> Decimal(1) / Decimal(7)
Decimal('0.1428571428571428571428571429')
round(z, 5)