Python decimal precision and rounding

Question

I want to limit the precision of my float and use it as an exact value for next operations, but I'm doing something wrong with decimal module.

from decimal import *

factor = 350/float(255)

# Settings
getcontext().prec = 1
getcontext().rounding = ROUND_UP

print Decimal(factor)

Python output: 1.372549019607843145962533526471816003322601318359375

Expected and wanted result: 1.4

Answer 1

From Python Documentation: ( https://docs.python.org/2/library/decimal.html )

The significance of a new Decimal is determined solely by the number of digits input. Context precision and rounding only come into play during arithmetic operations .

getcontext().prec = 6
Decimal('3.0')
Decimal('3.0')
Decimal('3.1415926535')
Decimal('3.1415926535')
Decimal('3.1415926535') + Decimal('2.7182818285')
Decimal('5.85987')
getcontext().rounding = ROUND_UP
Decimal('3.1415926535') + Decimal('2.7182818285')
Decimal('5.85988')

so you need to use decimal in operation, not when printing result.