Converts a control lib transfer function to sympy lib symbolic equation, uses x instead of s for the symbolic representation

tf_to_symbolic.py

def tf_to_symbolic_fraction(tf):
    x = symbols('x')
    num, den = tfdata(tf)
    num = num[0][0]
    den = den[0][0]
    counter = 1
    length_num = len(num)
    length_den = len(den)

    sym_num, sym_den = 0,0

    if(length_num == 0):
        raise ValueError ("The fraction num should not be empty")
    elif(length_den == 0 ):
        raise ValueError("The fraction den should not be empty")

    for i in range(length_num):
        sym_num+=num[i]*(x**(length_num - counter))
        counter += counter
    counter = 1
    for i in range(length_den):
        sym_den+=den[i]*(x**(length_den - counter))
        counter += counter
    return sym_num/sym_den

make sure to do the following imports:

from control import *
from sympy import *