python 2.7字符串格式为十进制为round函数

Question

I got a problem in string format function which I don't understand. Please help to explain why and how to fix this. thanks. ( python 2.7.3 , [GCC 4.6.3] on linux2 , ubuntu 12.04 x86 )

>>> import locale
>>> locale.format("%0.{0}f".format(2), 1.135, grouping=True)
'1.14'
>>> locale.format("%0.{0}f".format(2), 1.125, grouping=True)
'1.12'

>>> ("%0.2f")%(1.135)
'1.14'
>>> ("%0.2f")%(1.125)
'1.12'

I need the format result to match the round() function

>>> round(1.135, 2)
1.14
>>> round(1.125, 2)
1.13

Thank everyone.

Answer 1

That's because rounding is not simply bringing the last digit greater than 5 up, while truncating those lower than 4, since this method would introduce an increase in the expected average of rounded numbers.

The solution is to use Bankers' Rounding , that's what you see here.