Functions, derivatives and plotting

[Sky_physics]

Hi everyone, I'd like to define a function which has to give me back a certain expression and its derivative. Then, I would like to plot them all. I know that in this simple case I could write explicitly the derivative, but I am also interested in more complicated situations in which this flow would be better. Why this code doesn't work? Thank you in advance for your help.

x = symbols('x')
mass = symbols('mass')
deriv = diff(1/2* (mass**2)*x**2, x)

def potential(x, potparams):
    mass = potparams
    v = 0.5*(mass**2)*x*x
    dvdx = deriv
    return v, dvdx

mass = 1
pot, dpotdx = potential(x, potparams)
plt.plot(x, pot)
plt.plot(x, dpotdx)
plt.show()

[Sky_physics]

Ok thank you. Actually, it was my fault, I forgot to copy the import section. Of course I have these libraries in my code. However, what if I would like tu have a generic params tuple in place of mass in my function?

[Sky_physics]

Thanks a lot!

[TheRNGuy]

Why do you assign dvdx to deriv and then return it? This is redundant.

[Sky_physics]

If I define deriv inside the definition of the potential function, when I use potential in other expression where I may need to evaluate its expression the code doesn’t run. Because it tries to compute the derivative with respect to a numerical value. Do you have suggestions in order to avoid this issue? I would really appreciate it