Calculator Code Python

def searchChar(expr, char):
    parenthesisCounter = 0
    for i in range(len(expr)-1, -1, -1):
        if expr[i] == ")":
            parenthesisCounter += 1
        elif expr[i] == "(":
            parenthesisCounter -= 1
        elif expr[i] == char and parenthesisCounter == 0 and expr[i-1] not in ("*", "/", "-", "+", "^"):
            return i
    return -1

def calc(expr):
    try:
        return float(expr)
    except ValueError:
        pass

    searchingOrder = ["+", "-", "*", "/", "^"]
    for op in searchingOrder:
        idx = searchChar(expr, op)
        if idx != -1:
            left = expr[:idx]
            right = expr[idx+1:]
            if op == "+":
                if len(left) == 0:
                    left = "0"
                return calc(left) + calc(right)

            elif op == "-":
                if len(left) == 0:
                    left = "0"
                return calc(left) - calc(right)

            elif op == "*":
                return calc(left) * calc(right)

            elif op == "/":
                return calc(left) / calc(right)

            elif op == "^":
                return calc(left) ** calc(right)
    if expr[0] == "(":
        # Strip parenthesis from expr and calc
        return calc(expr[1:-1])