不知道怎样补全这个程序的代码

此程序是封装复数类，要求补全代码，请有会的人帮忙看一下该如何补全这个代码。谢谢。

class MyComplex(object):
    def __init__(self, x=0, y=0):
        self._a = x
        self._b = y

    def __add__(self, other):
        other = list(str(other))
        if 'i' not in other:
            a = eval(other)
            b = 0
        else:
            length = len(other)
            index = []
            for i in range(length):
                if other[i] in '+-':
                    index.append(i)
            if index[0] == 0:
                a = eval(''.join(other[index[0]:index[1]]))
                b = eval(''.join(other[index[1]:-1]))
            else:
                a = eval(''.join(other[:index[0]]))
                b = eval(''.join(other[index[0]:-1]))
        return MyComplex(x=self._a + a, y=self._b + b)

    def __sub__(self, other):
        other = list(str(other))
        if 'i' not in other:
            a = eval(other)
            b = 0
        else:
            length = len(other)
            index = []
            for i in range(length):
                if other[i] in '+-':
                    index.append(i)
            if index[0] == 0:
                a = eval(''.join(other[index[0]:index[1]]))
                b = eval(''.join(other[index[1]:-1]))
            else:
                a = eval(''.join(other[:index[0]]))
                b = eval(''.join(other[index[0]:-1]))
        return MyComplex(x=self._a - a, y=self._b - b)

    def __doubleOrInt__(self, num):
        if type(num) == int:
            return str(num)
        else:
            return "{.2f}".format(num)

    def __isOne(self, num):
        if num == "1":
            return ""
        elif num == "-1":
            return '-'
        else:
            return num

    def __str__(self):
        if self._b > 0:
            return f"{self._a}+{self._b}i"
        elif self._b == 0:
            return f"{self._a}"
        else:
            return f"{self._a}{self._b}i"


if __name__ == '__main__':
    one = MyComplex(1, 3)
    two = MyComplex(-2, 4)
    three = one.__add__(two)
    print("one=", one)
    print('two=', two)
    print('three=', three)

class MyComplex(object):
    def __init__(self,x=0,y=0):
        self.__a = x
        self.__b = y

    def __add__(self, other):
        x = self.__a + other.__a
        y = self.__b + other.__b
        return MyComplex(x, y)
        
    def __sub__(self, other):
        x = self.__a - other.__a
        y = self.__b - other.__b
        return MyComplex(x, y)

    def __str__(self):
        if self.__a==0:
            if self.__b==0:
                return '0'
            return f'{self.__b}i'
        if self.__b==0:
            return str(self.__a)
        sign = '+' if self.__b>0 else ''
        return f'{self.__a}{sign}{self.__isOne(self.__doubleOrInt(self.__b))}i'
            
    def __doubleOrInt(self, num):
        if type(num) == int:
            return str(num)
        else:
            return str(round(num,2))

    def __isOne(self, num):
        if num=='1':
            return ''
        elif num=='-1':
            return '-'
        else:
            return num

    def __repr__(self):
        return self.__str__() 


if __name__ == '__main__':
    
    num1 = MyComplex(  5,  7)
    num2 = MyComplex( -5, -1)
    num3 = MyComplex( -3, -7)

    print("num1 = " + str(num1))
    print("num2 = " + str(num2))
    print("num3 = " + str(num3))

    num4 = num1 + num2
    num5 = num2 - num3
    print("num1+num2 = " + str(num4))
    print("num2-num3 = " + str(num5))

''' out:
num1 = 5+7i
num2 = -5-5i
num3 = -3-7i
num1+num2 = 2i
num2-num3 = -2+2i
'''