Creating a new function as return in python function?

Question

I was wondering if it is possible in python to do the following:

def func1(a,b):    return func2(c,d) 

What I mean is that suppose I do something with a,b which leads to some coefficients that can define a new function, I want to create this function if the operations with a,b is indeed possible and be able to access this outside of func1.

An example would be a simple fourier series, F(x), of a given function f:

def fourier_series(f,N):    ...... math here......     return F(x) 

What I mean by this is I want to creat and store this new function for later use, maybe I want to derivate it, or integrate or plot or whatever I want to do, I do not want to send the point(s) x for evaluation in fourier_series (or func1(..)), I simply say that fourier_series creates a new function that takes a variable x, this function can be called later outside like y = F(3)... if I made myself clear enough?

Answer 1

You should be able to do this by defining a new function inline:

fourier_series(f, N):     def F(x):         ...     return F 

You are not limited to the arguments you pass in to fourier_series:

def f(a):     def F(b):         return b + 5     return F  >>> fun = f(10) >>> fun(3) 8 

Answer 2

You could use a lambda (although I like the other solutions a bit more, I think :) ):

>>> def func2(c, d): ...   return c, d ... >>> def func1(a, b): ...   c = a + 1 ...   d = b + 2 ...   return lambda: func2(c,d) ... >>> result = func1(1, 2) >>> print result <function <lambda> at 0x7f3b80a3d848> >>> print result() (2, 4) >>>