Python: getting a reference to a function from inside itself

Question

If I define a function:

def f(x):
    return x+3

I can later store objects as attributes of the function, like so:

f.thing="hello!"

I would like to do this from inside the code of the function itself. Problem is, how do I get a reference to the function from inside itself?

Answer 1

The same way, just use its name.

>>> def g(x):
...   g.r = 4
...
>>> g
<function g at 0x0100AD68>
>>> g(3)
>>> g.r
4

Answer 2

If you are trying to do memoization, you can use a dictionary as a default parameter:

def f(x, memo={}):
  if x not in memo:
    memo[x] = x + 3
  return memo[x]

Answer 3

Or use a closure:

def gen_f():
    memo = dict()
    def f(x):
        try:
            return memo[x]
        except KeyError:
            memo[x] = x + 3
    return f
f = gen_f()
f(123)

Somewhat nicer IMHO