python - Python程序，谁能告诉我这里的2有什么意义？

Question

在 round 函数中，作为第二个参数的数字 2 是什么意思？

##This is a program that calcs your credit card, and compounds down the total

a=float(raw_input("Enter the outstanding balance on your credit card:"))
b=float(raw_input("Enter the annual crdit card interest rate as a deicimal:"))           
c=float(raw_input("Enter the minimum monthly payment as a decimal:"))
for month in range(1, 13):
    print "Month: ", str(month)
    MMP = round((c * a),2)                  ##the 2 here and below, what does it do?
    print "Minimum monthly payment: ", MMP
    IP = round((b/12 * a),2)
    print "Interest payed: ", IP 
    PP = round(((c*a) - ((b/12)*a)),2)
    print "principal payed: ", PP
    a = round((a - PP),2)
    print "Remaining balance", a 

Answer 1

2 作为第二个参数传递给round，给出要四舍五入的小数位数。这会将它四舍五入到最接近的浮点数，表示四舍五入到小数点后两位的数字。请注意，这是一个非常糟糕的主意，也是常见的错误来源。请改用 fractions.Fraction 或 decimal.Decimal。

浮点数永远不应该用来赚钱，尤其是当你像这样四舍五入时。

Answer 2

2是在舍入操作中使用的小数位数。看看这里：http ://docs.python.org/library/functions.html#round

Answer 3

这会将一个数字四舍五入，以便在操作后它有 2 个十进制数字。检查以下文档：

http://docs.python.org/library/functions.html#round