Calculate derivative for provided function, using finite difference, Python -

i should start saying relatively new python, have coded in java , matlab before.

in python, code

def func(f):     return f g = func(cos) print(g(0)) 

gives result

>1.0 

as g defined cosine function.

i want write function calculates derivative of provided function using finite difference approach. function defined as

def derivator(f, h = 1e-8): 

and achieve follwing:

g = derivator(cos) print(g(0)) # should 0 print(g(pi/2)) # should -1 

at moment derivator function looks this

def derivator(f, h = 1e-8):     return (f(x+h/2)-f(x-h/2))/h 

which wrong, not sure how should fix it. thoughts?

your current derivator() function (which should called differentiator()) uses undefined variable x , return single value, if x defined--the value of f'(x). want return function takes x value. can define inner function , return it:

def fprime(x):     return (f(x+h/2)-f(x-h/2))/h return fprime 

because don't use function anywhere else, though, can use lambda instead, shorter:

return lambda x: (f(x+h/2)-f(x-h/2))/h 

the thing pep 8 says lambdas should not assign result of lambda variable, return it:

fprime = lambda x: (f(x+h/2)-f(x-h/2))/h  # don't this! return fprime