python实现四舍五入

由于python的round进行四舍五入时是遇六进一而不是遇五进一，所以要从新编写一个算法
具体代码如下
#coding:utf-8

class round(object):

    #返回浮点数类型的值
    def roundF(self, value, digit):
        result = str(value)
        if (float(value) < 0):
            result = result[1:]
            if (result != ''):
                indexDec = result.find('.')
                if (indexDec > 0):
                    decimal = result[indexDec + 1:]
                    decimalCount = len(decimal)
                    if (decimalCount > digit):
                        xiaoshu = result[indexDec + digit + 1]  # 第digit+1位小数
                        if (int(xiaoshu) > 4):
                            result = str(float(value) * -1 + pow(10, digit * -1))
                            # 存在进位的可能，小数点会移位
                            indexDec = result.find('.')
                            result = result[:indexDec + digit + 1]
                        else:
                            result = result[:indexDec + digit + 1]
                    else:
                        lens = digit - len(result[indexDec:]) + 1
                        for i in range(lens):
                            result += '0'
            result = float(result) * -1
            return result
        else:
            if (result != ''):
                indexDec = result.find('.')
                if (indexDec > 0):
                    decimal = result[indexDec + 1:]
                    decimalCount = len(decimal)
                    if (decimalCount > digit):
                        xiaoshu = result[indexDec + digit + 1]  # 第digit+1位小数
                        if (int(xiaoshu) > 4):
                            result = str(float(value) + pow(10, digit * -1))
                            # 存在进位的可能，小数点会移位
                            indexDec = result.find('.')
                            result = result[:indexDec + digit + 1]
                        else:
                            result = result[:indexDec + digit + 1]
                    else:
                        lens = digit - len(result[indexDec:]) + 1
                        for i in range(lens):
                            result += '0'
            return float(result)

    #返回字符串类型的值
    def roundStr(self,value, digit):
        result = str(value)
        if (float(value) < 0):
            result = result[1:]
            if (result != ''):
                indexDec = result.find('.')
                if (indexDec > 0):
                    decimal = result[indexDec + 1:]
                    decimalCount = len(decimal)
                    if (decimalCount > digit):
                        xiaoshu = result[indexDec + digit + 1]  # 第digit+1位小数
                        if (int(xiaoshu) > 4):
                            result = str(float(value) * -1 + pow(10, digit * -1))
                            # 存在进位的可能，小数点会移位
                            indexDec = result.find('.')
                            result = result[:indexDec + digit + 1]
                        else:
                            result = result[:indexDec + digit + 1]
                    else:
                        lens = digit - len(result[indexDec:]) + 1
                        for i in range(lens):
                            result += '0'
            # result = float(result) * -1
            return '-'+result
        else:
            if (result != ''):
                indexDec = result.find('.')
                if (indexDec > 0):
                    decimal = result[indexDec + 1:]
                    decimalCount = len(decimal)
                    if (decimalCount > digit):
                        xiaoshu = result[indexDec + digit + 1]  # 第digit+1位小数
                        if (int(xiaoshu) > 4):
                            dg=pow(10, digit * -1)
                            result = str(float(value) +dg )
                            # 存在进位的可能，小数点会移位
                            indexDec = result.find('.')
                            result = result[:indexDec + digit + 1]
                        else:
                            result = result[:indexDec + digit + 1]
                    else:
                        lens = digit - len(result[indexDec:]) + 1
                        for i in range(lens):
                            result += '0'
            return result

if __name__ == '__main__':
    d=round().roundStr(2346.23502,4)
    print(d)