I have a function that returns an array:
def fun(x,a):
return [a*x,a*x**2]
and I want to integrate it (using scipy quad):
def integrate(a):
return quad(fun[0],0,1,args=a)
print integrate(1)
This gives TypeError: 'function' object is not subscriptable.
What's the right, pythonic way to do this?
Create a wrapper function around fun to select an element of the array. For example, the following will integrate the first element of the array.
from scipy.integrate import quad
# The function you want to integrate
def fun(x, a):
return np.asarray([a * x, a * x * x])
# The wrapper function
def wrapper(x, a, index):
return fun(x, a)[index]
# The integration
quad(wrapper, 0, 1, args=(1, 0))
Following @RobertB's suggestion, you should avoid defining a function int because it messes with the builtin names.
Your function returns an array, integrate.quad needs a float to integrate. So you want to give it a function that returns one of the elements from your array instead of the function itself. You can do that via a quick lambda:
def integrate(a, index=0)
return quad(lambda x,y: fun(x, y)[index], 0, 1, args=a)
ax?fun[0]is trying to subscript the function. Did you want to subscript the results of the function? In that case the syntax isfun(param1, param2)[0]funis your funciton, notfun[0]. Also, do not call the second function "int" since that clobbers the standard python "int" type in your namespace.