Python float round error 117.285 round to 117.28 not 117.29

Question

I am using python 2.7, and the code I have is:

a = 10.5 * 22.34 / 2.0
print \"%.2f\" % a

and the result I expect is 117.29, but it shows 11

Answer 1

Mr. Skeet has the correct answer, below is an example of how to use the decimal module to which he refers:

import decimal
a = decimal.Decimal('117.285')
rounded = a.quantize(decimal.Decimal('.01'), rounding=decimal.ROUND_HALF_UP)
print rounded
# 117.29
repr(rounded)
# "Decimal('117.29')"