如何摆脱Python sympy中的垂直渐近线？

Question

I try to compute the second derivative of f(x) = x**2 / (x-1) using Sympy package but the vertical asymptote appeared as if x were approaching to 1. How do I get rid of that? Here is my code:

import sympy as sp
import numpy as np
import pylab as pyl 

t = sp.symbols('t')
def fp(t):
    return t**2 / (t -1)
f = sp.lambdify(t, fp(t), modules=['numpy'])

dp = sp.diff(fp(t))
d2p = sp.diff(dp)
d2 = sp.lambdify(t, d2p, modules=['numpy'])

x = np.linspace(-7.5, 10, 10**3)

pyl.plot(x, d2(x), 'b-')

pyl.ylim(-6, 10)
pyl.grid()

pyl.show()

Vertical asymptote at x=1

Answer 1

I would try a second derivative in the same call:

d2p = sp.diff(t**2 / (t-1), t, 2)

and see if that makes a difference. You can also evaluate d2p and see what is the value of d2p(1) .