scipy.integrate.quad giving ValueError: invalid callable given

I have to define a function that includes an integral but it keeps giving me this error

ValueError: invalid callable given

Here is the code I used

import numpy as np
from scipy.integrate import quad

def w(x, w0):
    return w0*(1+x)

def fun(x, w0, H_i):
    f = ( 3 * (1+w(w0, x)) ) / ( 1+x )
    return quad(f,np.inf,0) + 2*np.log(H_i)

When I try this function with any value it always gives me that error. What can I do to fix this? Thank you very much and have a nice day

The "ValueError: invalid callable given" error you're seeing means that the code is having trouble with the argument you passed to the quad function. This function expects a callable function that takes a single argument and returns a float. However, in your fun function, you're actually passing in the quad function itself as the first argument.

To fix this, you should modify your fun function to define a new function that takes a single argument and returns the value of the integrand. You can then pass this new function to the quad function.

Here's an example of how you could modify your code to achieve this:

def fun(x, w0, H_i):
    def integrand(t):
        return ( 3 * (1+w(w0, t)) ) / ( 1+t )
    
    result, _ = quad(integrand, np.inf, x)
    return result + 2*np.log(H_i)

In this modified fun function, we define a new function integrand that takes a single argument t and returns the integrand function. We then pass this integrand function to the quad function as the first argument.

By making these changes, your fun function should work correctly without throwing the "invalid callable" error.

Hope this helps!