给你一个string和x的value让你解出y的值

比如'2x - ((x - (3x + 1) + 2) + 3) + 4 = x + y'

def caculate(s, xVal):
    l, r = s.split('=')
    lNumX, lNumY, lNum = processOneSide(l, 1)
    rNumX, rNumY, rNum = processOneSide(r, -1)
    x = (lNumX + rNumX)*xVal
    yDigit = lNumY + rNumY
    return (-x-(lNum+rNum))/float(yDigit)

def processOneSide(s, globalSign):
    numX = 0
    numY = 0
    num = 0

    tmpNum = 0
    sign = 1
    stack = []
    cur_sign = 1
    for i, c in enumerate(s):
        if c.isdigit():
            tmpNum = tmpNum*10 + int(c)
        elif c=='x':
            if not tmpNum:
                numX += 1*sign*cur_sign
            else:
                numX += tmpNum*sign*cur_sign
                tmpNum = 0
        elif c=='y':
            if not tmpNum:
                numY += 1*sign*cur_sign
            else:
                numY += tmpNum*sign*cur_sign
                tmpNum = 0
        elif c in '+-':
            num += tmpNum*sign*cur_sign
            sign = [-1, 1][c=='+']
            tmpNum = 0
        elif c in '(':
            stack.append(sign)
            cur_sign *= sign
            sign = 1
        elif c in ')':
            if i == len(s)-1:
                num += tmpNum*sign*cur_sign
                tmpNum = 0
            cur_sign *= stack.pop()
            sign = 1


    if tmpNum != 0:
        print (sign, cur_sign)
        num += tmpNum*sign*cur_sign

    return (globalSign*numX, globalSign*numY, globalSign*num)


# s = '2x - (4x+ y) = 1'
# print caculate(s, 1)
s = '2x - ((x - (3x + 1) + 2) + 3) + 4 = x + y'

1 - 2 - 3 + 4
print caculate(s, 1)