Python standard library - decimal numbers and mathematical module of Introduction to use

Standard library - numbers and mathematical module of the decimal use Description

by: award-off QQ : 1033553122

example

>>>from decimal import *

>>>getcontext()

Context(prec=28, rounding=ROUND_HALF_EVEN, Emin=-999999, Emax=999999, capitals=1, clamp=0, flags=[], traps=[InvalidOperation, DivisionByZero, Overflow])

 

>>>Decimal('5')/3

Decimal('1.666666666666666666666666667')

 

>>> getcontext (). Prec = 6 # setting accuracy, i.e. the maximum number of decimal places

 

>>>Decimal('5')/3

Decimal('1.66667')

>>>getcontext().prec = 2

>>>Decimal('5')/3

Decimal('1.7')

>>>Decimal('5')/Decimal(3)

Decimal('1.7')

 

>>>Decimal('3.14')

Decimal('3.14')

 

>>>Decimal('3.14') * Decimal(0.5)

Decimal('1.570')

 

>>>Decimal('3.1415926535')

Decimal('3.1415926535')

 

>>>Decimal('NaN')

Decimal ( 'in')

 

>>>Decimal('-Infinity')

Decimal('-Infinity')

 

Conclusion: if and only if the accuracy of "calculation result" exceeds the number of decimal places getContext () set at the time, it will exceed the accuracy of decimal places truncated portion