Banker's rounding

Question

Please tell me, are there any ways of classic rounding in Python 3?

Answer 1

Oh sorry, Aymane Boukrouh. My mistake. Alisa🌸🌸, there are no built-in functions to do what you're talking about, but you can create a custom function:
import math
def bankers_rounding(num):
if math.floor(num) % 2 == 0: #if rounding down num returns an even number
return math.floor(num)
else:
return math.ceil(num)

Answer 2

Thank you, it was so easy

Answer 3

Abhishek Sahoo, This is really useful and may come in handy, thank you :)

Answer 4

You're welcome.

Answer 5

Jianmin Chen 你好，can you please test your solution against test cases of 4.6 and 5.3?

Answer 6

https://code.sololearn.com/ccPlRd5ZSdyj/?ref=app

Alisa🌸🌸 Please let me know if it's helpful

Answer 7

Gordon , I'm pretty sure the program works correctly for those two numbers. 4.6 will return 4, and 5.3 will return 6.

By the way, 你好吗？我会说中文和英文。😃

Answer 8

Jianmin Chen 我也會中文呀

banker's rounding 的話，4.6還是應該進位為5，5.3還是應該捨棄為5。只有.5時才要找最接近雙數，來平衡多次加減的誤差bias。

見：
https://en.m.wikipedia.org/wiki/Rounding

引用一：

Round half to even Edit
A tie-breaking rule without positive/negative bias and without bias toward/away from zero is round half to even. By this convention, if the fractional part of x is 0.5, then y is the even integer nearest to x. Thus, for example, +23.5 becomes +24, as does +24.5; while −23.5 becomes −24, as does −24.5. This function minimizes the expected error when summing over rounded figures, even when the inputs are mostly positive or mostly negative.

This variant of the round-to-nearest method is also called convergent rounding, statistician's rounding, Dutch rounding, Gaussian rounding, odd–even rounding,[6] or bankers' rounding.

解決的問題，見 Vancouver Stock Exchange那段。

Answer 9

Jianmin Chen yes it is correct banker's rounding now~ 👏

甭客气～

Answer 10

Gordon, I see my error! Thanks for informing me, I wouldn't have known. So, Alisa🌸🌸, this means the correct code is:
import math
def bankers_rounding(num):
if (num - 0.5).is_integer() and (num + 0.5).is_integer(): #if number is exactly between two whole numbers
if math.floor(num) % 2 == 0: #if rounding down returns an even number
return math.floor(num)
else:
return math.ceil(num)
else:
return round(num) #if not exactly between two whole numbers, return the normally rounded amount
I believe that's my mistake, right? The number had to be exactly between two whole numbers in order to be rounded in the bankers' rounding method.

谢谢, Gordon.