Issue
I can't figure out how to specify my decimal precision for logs, importing decimal and setting the context does not affect the log functions.
from decimal import *
getcontext().prec = 54
print(Decimal(197)/ Decimal(83))
2.37349397590361445783132530120481927710843373493975904
print(math.log(Decimal(197)))
5.2832037287379885
I would like to set a high precision for functions other than fractions. Python 3 btw.
Solution
Possible solutions:
String formatting:
- f-strings have the benefit of not requiring another package to be imported
- f-Strings: A New and Improved Way to Format Strings in Python
- Extend the decimal places shown, to the same extent as the
decimal
module
x = 4567.09710599898797936589076897
y = 2445.89790870380808990080797897
Lengthen:
print(f'{(x/y):.054f}')
>>> 1.867247643389702504990168563381303101778030395507812500
calculation = math.log(197)
print(f'{calculation:.050f}')
>>> 5.28320372873798849155946300015784800052642822265625
Shorten:
print(f'{(x/y):.02f}')
>>> 1.87
numpy
:
Shorten:
print(np.round(x/y, 2))
>>> 1.87
Lengthen:
numpy
does not extend the precision shown, beyond what's shown by python.
print(np.around(x/y, 54))
>>> 1.8672476433897025
print(x/y)
>>> 1.8672476433897025
decimal
Module:
Example from the question:
print(math.log(197))
>>> 5.2832037287379885
print(math.log(Decimal(197.0)))
>>> 5.2832037287379885
print(Decimal(math.log(197)))
>>> 5.28320372873798849155946300015784800052642822265625
print(Decimal(197).ln())
>>> 5.283203728737988506779797329
print(f'{math.log(197):.050f}')
>>> 5.28320372873798849155946300015784800052642822265625
Notes:
- Either method can be used to format the number to the required decimal place, prior to writing into a log.
- Caveat: due to the way numbers are represented in computers, I'm doubtful if increasing the number of decimal places shown, increases the precision.
- Using
f-strings
provided the same final output precision as using thedecimal
module.
Answered By - Trenton McKinney Answer Checked By - Willingham (PHPFixing Volunteer)
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