問題描述
假設我有 8.8333333333333339，我想將其轉換為 8.84.如何在 Python 中完成此操作?
round(8.8333333333333339, 2) 給出 8.83 而不是 8.84.我是 Python 或一般編程新手.
我不想把它打印成字符串，結果會被進一步使用.有關該問題的更多信息，請查看
從示例輸出看來，他們四舍五入每月付款，這就是許多人所說的上限函數的效果.這意味著每個月支付的總金額略多于 1?12.這使得最后的付款比平時少了一點——剩下的未付余額只有 8.76.
使用正常舍入產生 8.83 的每月付款和 8.87 稍高的最終付款同樣有效.然而，在現實世界中，人們通常不喜歡他們的付款增加，因此將每筆付款四舍五入是常見的做法——它也可以更快地將錢還給貸方.
Suppose I have 8.8333333333333339, and I want to convert it to 8.84. How can I accomplish this in Python?
round(8.8333333333333339, 2) gives 8.83 and not 8.84. I am new to Python or programming in general.
I don't want to print it as a string, and the result will be further used. For more information on the problem, please check Tim Wilson's Python Programming Tips: Loan and payment calculator.
8.833333333339 (or 8.833333333333334, the result of 106.00/12) properly rounded to two decimal places is 8.83. Mathematically it sounds like what you want is a ceiling function. The one in Python's math module is named ceil:
import math
v = 8.8333333333333339
print(math.ceil(v*100)/100) # -> 8.84
Respectively, the floor and ceiling functions generally map a real number to the largest previous or smallest following integer which has zero decimal places — so to use them for 2 decimal places the number is first multiplied by 102 (or 100) to shift the decimal point and is then divided by it afterwards to compensate.
If you don't want to use the math module for some reason, you can use this (minimally tested) implementation I just wrote:
def ceiling(x):
n = int(x)
return n if n-1 < x <= n else n+1
How all this relates to the linked Loan and payment calculator problem:
From the sample output it appears that they rounded up the monthly payment, which is what many call the effect of the ceiling function. This means that each month a little more than 1?12 of the total amount is being paid. That made the final payment a little smaller than usual — leaving a remaining unpaid balance of only 8.76.
It would have been equally valid to use normal rounding producing a monthly payment of 8.83 and a slightly higher final payment of 8.87. However, in the real world people generally don't like to have their payments go up, so rounding up each payment is the common practice — it also returns the money to the lender more quickly.
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