数字修约值

数字修约  4舍6入 5看后  没后就看单双
def rv(a,k):
    a = str(a)
    if "." in a:
        b = a.find(".")
        if len(a[b + 1:]) <= k:  # 防止低位小数修正为高位小数
            a = a + "0" * (k - len(a[b + 1:]))
        else:
            m = a[b + k+1:]
            if int(m) > 5 * 10 ** (len(a) - (b + k + 2)):
                if a[b + k] == ".":
                    a = a[:b + k - 1] + str(int(a[b + k - 1]) + 1)
                else:
                    a = str(int(a[:b+k+1].replace(".", ""))+1)
                    a = a[:b] + "."+a[b:]
            elif int(m) == 5 * 10 ** (len(a) - (b + k + 2)):
                if a[b + k] == ".":
                    if int(a[b + k - 1]) / 2 == 0:
                        a = a[:b + k]
                    else:
                        a = str(int(a[:b + k + 1].replace(".", "")) + 1)
                        a = a[:b] + "." + a[b:]
                elif int(a[b + k]) / 2 == 0:
                    a = a[:b + k + 1]
                    # print(a)
                else:
                    a = a[:b + k] + str(int(a[b + k]) + 1)
            else:
                if a[b + k] == ".":
                    a = a[:b + k]
                else:
                    a = a[:b + k + 1]
    else:
        if k > 0:
            a = a + "." + "0" * k
        elif k == 0:
            a = a
    return a
for jj in range(15):
    print(jj,rv(1.99999998888,jj))