py2 vs py3 addition output difference in float format

Question

a = 310.97
b = 233.33
sum= 0.0
for i in [a,b]:
    sum += i
print(sum)

py2 o/p: 544.3

py3 o/p: 544.3000000000001

Any way to report py3 output as same as py2 with futurizing? without using round-off ?

Answer 1

You could convert the values to integers before performing the operation and afterwards divide by a constant e.g. 100.0 in this case.

a = 310.97
b = 233.33
c = int(a * 100)
d = int(b * 100)
sum = 0
for i in [c,d]:
    sum += i
result = sum / 100.0
print(result)  # 544.3

The reason for the difference is the precision in the conversion from float to string in the two versions of Python.

a = 310.97
b = 233.33
sum = 0.0
for i in [a,b]:
    sum += i
print("{:.12g}".format(x)) # 544.3

See this answer for further details: Python format default rounding when formatting float number