Derivative Calculator (Still In Development)

operator = ["(", ")", "/", "*", "+", "-", "^"]
priorityDict = {"+": 1, "-": 1, "*": 2, "/": 2, "(": 0, "^": 3}


def refine(f):
    f = "".join(f.strip().split())
    print(f)
    result = ""
    for char in f:
        if char in operator:
            result += " " + char + " "
        else:
            result += char
    return result.strip()


def getPriority(operator):
    return priorityDict[operator]


def toPostfix(f):
    result = []
    stack = []

    def processWord(word):
        if word not in operator:
            result.append(word)
        else:
            if word == "(":
                stack.append(word)
            elif word == ")":
                char = ""
                while char != "(":
                    char = stack.pop()
                    if char != "(":
                        result.append(char)
            elif word in ["+", "-", "*", "/", "^"]:
                while stack and getPriority(word) <= getPriority(stack[-1]):
                    result.append(stack.pop())
                stack.append(word)
    for word in f.split():
        processWord(word)
    while stack:
        result.append(stack.pop())
    return result


def toInfix(fStack):
    stack = []
    for index, item in enumerate(fStack):
        if item not in operator:
            stack.append(item)
        else:
            first = stack.pop()
            second = stack.pop()
            stack.append("( " + second + " " + item + " " + first + " )")
    return stack[0]


def getExp(fStack):
    stack = []
    for index, item in enumerate(fStack):
        if item not in operator:
            stack.append(item)
        else:
            if index == len(fStack) - 1:
                exp1 = toPostfix(refine(stack.pop()))
                exp2 = toPostfix(refine(stack.pop()))
                return (exp2, exp1)
            else:
                first = stack.pop()
                second = stack.pop()
                stack.append("( " + second + " " + item + " " + first + " )")


def getDerivative(fStack):
    if len(fStack) == 1:
        if fStack[0] == "x":
            return ["1"]
        elif fStack[0].isnumeric:
            return ["0"]
    else:
        _operator = fStack[-1]
        exp1, exp2 = getExp(fStack)
        derivative1, derivative2 = getDerivative(exp1), getDerivative(exp2)
        print("Derivatives: ")
        print(derivative1)
        print(derivative2)
        if _operator == "+":
            return derivative1 + derivative2 + ["+"]
        elif _operator == "-":
            return derivative1 + derivative2 + ["-"]
        elif _operator == "*":
            firstExp = derivative1 + exp2 + ["*"]
            secondExp = derivative2 + exp1 + ["*"]
            return firstExp + secondExp + ["-"]
        elif _operator == "/":
            firstExp = derivative1 + exp2 + ["*"]
            secondExp = derivative2 + exp1 + ["*"]
            numerator = firstExp + secondExp + ["-"]
            denominator = secondExp + ["2"] + ["^"]


print("Derivative Calculator Beta (default June 14) :: Tran Viet Anh")
print("type 'operator' for help and list of math operation")
print("f(x) = ", end="")
function = input()

function = refine(function)
print("Refined function: ", function)
toPostfix(function)
postFixStack = toPostfix(function)
print("Postfix stack: ", postFixStack)
derivativeResult = getDerivative(postFixStack)
print(toInfix(derivativeResult))