round(value, 2) 有什么作用？答案

【问题标题】：What does round(value, 2) do?round(value, 2) 有什么作用？
【发布时间】：2015-07-23 23:16:49
【问题描述】：

我目前正在通过 MIT OCW 参加免费的在线课程。我遇到了某个问题，我正在尝试了解解决方案。我不确定“2”在做什么。是 (minMonthlyPaymentRate * balance, 2) 中的两个，解决方法如下：

# 6.00 PS1-A Solution
# Determines remaining credit card balance after a year of making the minimum payment each month

balance = float(raw_input("Enter the outstanding balance on your credit card: "))
annualInterestRate = float(raw_input("Enter the annual credit card interest rate as a decimal: "))
minMonthlyPaymentRate = float(raw_input("Enter the minimum monthly payment rate as a decimal: "))

# Monthly Interest Rate
monthlyInterestRate = annualInterestRate/12

# Initialize state variables
numMonths = 1
totalAmtPaid = 0

while numMonths <= 12:
    # Minimum monthly payment of balance at start of the month
    minPayment = round(minMonthlyPaymentRate * balance,2)**This Two!?**
    totalAmtPaid += minPayment

    # Amt of monthly payment that goes to interest
    interestPaid = round(monthlyInterestRate * balance,2)

    # Amt of principal paid off
    principalPaid = minPayment - interestPaid

    # Subtract monthly payment from outstanding balance
    balance -= principalPaid

    print "Month:", numMonths
    print "Minimum monthly payment:", minPayment
    print "Remaining balance:", balance

    # Count this as a new month     
    numMonths += 1

print "RESULT"
print "Total amount paid:",totalAmtPaid
print "Remaining balance:",balance

【问题讨论】：

查看docs，它四舍五入到位数，在本例中为 2
它只是说结果应该四舍五入到小数点后两位...
好的，谢谢。这是有道理的。
您自己在文档中找不到这个？
你能把例子减少到一行吗？

标签： python rounding

【解决方案1】：

正如python documentation of the function round() 中所见，它声明“四舍五入到小数点后的 ndigits 位”。所以这意味着结果将四舍五入到小数点后两位数。

【讨论】：

【解决方案2】：

一张图抵千言。

【讨论】：

【解决方案3】：

round() 四舍五入到给定的位数并返回浮点数。

示例代码：

val=2.665
print(round(val, 2);

output:
6.67

【讨论】：