Need precision out to 25th decimal, Python keeps rounding down when computing-CodePudding

My code is essentially: arrA=arrB-arrC*varD. However, what happens after running that is that arrA ≠ arrB-arrC*varD, and instead arrA = arrB. I think arrC*varD is getting dropped off since it's super small, like 1e-20 at some point. However, arrA is also at like 1e-14 and I really need that precision. The arrays are float64, so I'm not sure why they're getting rounded and dropped off like that in computing.

Does anyone know how I can avoid this and keep precision out to at least the 25th decimal place? I've tried np.around to the 25th place but that's not helping either.

CodePudding user response：

use the python "decimal" module

    from decimal import *
    getcontext().prec = 30 #digits of precision that you want for your decimal object (default is 28)
    x = Decimal(1.2342346235723451432)/Decimal(4.326243232) #just an example problem -- just declare each value in your expression as a "Decimal" type to hold their precision
    #x is now a Decimal type object with precision of 30

CodePudding user response：

This has got to be already answered, think of a similar situation -pi

In intro to CS we went over this but there’s much easier methods, the simplest(laziest