Return a function with parameters

Question

I am trying to make a function that returns itself with parameters.

Def a (x,y):
   *code*
   Return a(x,y)

this returns an error when I try to run it.

>>> a(1,2)
RecursionError: maximum recursion depth exceeded

What I want is

>>> a(1,2)
a(1,2)

It there a way to return the function with parameters?

I know it can be done but I don’t know how to do it

>>> datetime.time(0,0)
Datetime.time(0,0)

Edit: Preferably I would like not to have to import any modules

You're getting the error because the function just keeps calling itself, until the maximum recursion depth (to prevent a stack overflow). Why would you want to this? — rpm192, Sep 27 '19 at 14:14
What you want to do is recursion without base condition? Please look into if this is exactly what you want to do. — Poojan, Sep 27 '19 at 14:17
As @wjandrea is saying, it looks like you're after a `__repr__` from a class, not a function. — Hampus Larsson, Sep 27 '19 at 14:24

score 1 · Answer 1 · answered Sep 27 '19 at 14:17

1

It looks like you have no valid return. The error means it calls itself so many times python just gives up. Example (good) will end after ''num'' times:

def a(x, num):
  if num == 0:
    return x
  return a(x + 1, num - 1)

Example (bad) will never return anything else as itself:

def a(x, num):
  if num == 0:
    return x
  return a(x + 1, num)

answered Sep 27 '19 at 14:17

Tom Nijhof

542
4
11

This is also known as a "bootstrap condition" in the recursive function. – KDecker Sep 27 '19 at 14:21

score 0 · Answer 2 · answered Sep 27 '19 at 14:17

Assuming you mean you want it to return a string representation of the function as called:

def a (x,y):
   *code*
   return f"a({x},{y})"

Alternatively if you are not able to use f-strings:

def a (x,y):
   *code*
   return "a({x},{y})".format(x=x, y=y)

score 0 · Accepted Answer · answered Sep 27 '19 at 14:30

I think you've misunderstood what is "returned" when you call the following row:

>>> datetime.time(0,0)
Datetime.time(0,0)

The original call datetime.time(0,0) creates a datatime-object to the console. Because you're not saving the returned object, the console automatically calls for the class-method called __repr__.

To replicate the behavior we can create the following class:

>>> class a:
...   def __init__(self, x,y):
...     self.x = x
...     self.y = y
...   def __repr__(self):
...     return "a({},{})".format(self.x, self.y)
...
>>> a(1,2)
a(1,2)

score 0 · Answer 4 · answered Sep 27 '19 at 14:35

0

Maybe using a nested function or lambda ?

$ python -q
>>> def a(x,y):
...     def _a():
...             return x + y
...     return _a
... 
>>> a(1,2)
<function a.<locals>._a at 0x7f048329e560>
>>> a(1,2)()
3

answered Sep 27 '19 at 14:35

Charles Paulet

191
1
2

Return a function with parameters

4 Answers4