First order derivation of standard algebraic polynomial in python

first_order_derivation.py

import re
x = "x**4 + 33*x**3 - 23*x**2 + 2*x + 1"
def first_order(x):
    res = ''
    for sign, coef, expo in re.findall("([\+-]?)\s?(\d+?)?\*?x\*?\*?(\d?)", '+' + x):
        if coef == "":
            coef = "1"
        coef = int(sign + coef)
        if expo == "":
            expo = "1"
        expo = int(expo)
        print(sign, coef, expo)
        
        new_coef = coef * expo
        new_expo = expo - 1
        if new_coef > 0:
            res += '+'
        if new_expo == 0:
            res += f"{new_coef}"
        elif new_expo == 1:
            res += f"{new_coef}*x"
        else:
            res += f"{new_coef}*x**{new_expo}"
            
    if res[0] == "+":
        res = res[1:]
    res = res.replace("+", " + ")
    res = res.replace("-", " - ")
    return res


mel = first_order(x)
print(mel)