it should still fix some issue Why did you just show a bit the error? Why not the full message, maybe even the full traceback!

code :

```
In [60]: sys = signal.lti(num_c, den_c)
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-60-21f71ecd8884> in <module>
----> 1 sys = signal.lti(num_c, den_c)
/usr/local/lib/python3.6/dist-packages/scipy/signal/ltisys.py in __init__(self, *system, **kwargs)
590 self._den = None
591
--> 592 self.num, self.den = normalize(*system)
593
594 def __repr__(self):
/usr/local/lib/python3.6/dist-packages/scipy/signal/filter_design.py in normalize(b, a)
1609 leading_zeros = 0
1610 for col in num.T:
-> 1611 if np.allclose(col, 0, atol=1e-14):
1612 leading_zeros += 1
1613 else:
<__array_function__ internals> in allclose(*args, **kwargs)
/usr/local/lib/python3.6/dist-packages/numpy/core/numeric.py in allclose(a, b, rtol, atol, equal_nan)
2169
2170 """
-> 2171 res = all(isclose(a, b, rtol=rtol, atol=atol, equal_nan=equal_nan))
2172 return bool(res)
2173
<__array_function__ internals> in isclose(*args, **kwargs)
/usr/local/lib/python3.6/dist-packages/numpy/core/numeric.py in isclose(a, b, rtol, atol, equal_nan)
2267 y = array(y, dtype=dt, copy=False, subok=True)
2268
-> 2269 xfin = isfinite(x)
2270 yfin = isfinite(y)
2271 if all(xfin) and all(yfin):
TypeError: ufunc 'isfinite' not supported for the input types, and the inputs could not be safely coerced to any supported types according to the casting rule ''safe''
```

```
In [55]: num_c[0]
Out[55]: 500000.000000000
In [56]: type(_)
Out[56]: sympy.core.numbers.Float
```

```
In [61]: np.array(num_c)
Out[61]: array([500000.000000000], dtype=object)
```

```
In [63]: np.array(num_c).astype(float)
Out[63]: array([500000.])
```

```
In [64]: sys = signal.lti(np.array(num_c).astype(float), np.array(den_c).astype(float))
In [65]: sys
Out[65]:
TransferFunctionContinuous(
array([100200.4008016]),
array([1.00000000e+00, 1.02004008e+05]),
dt: None
)
```

```
sys = signal.lti([float(i) for i in num_c],[float(i) for i in den_c])
```