Question

Consider the following (broken) code:

import functools                                                            
class Foo(object):                                                          
  def __init__(self):                                                 
    def f(a,self,b):                                            
      print a+b                                           
    self.g = functools.partial(f,1)                             
x=Foo()                                                                     
x.g(2)

What I want to do is take the function f and partially apply it, resulting in a function g(self,b). I would like to use this function as a method, however this does not currently work and instead I get the error

Traceback (most recent call last):
  File "test.py", line 8, in <module>
    x.g(2)
TypeError: f() takes exactly 3 arguments (2 given)

Doing x.g(x,2) however works, so it seem the issue is that g is considered a “normal” function instead of a method of the class. Is there a way to get x.g to behave like a method (i.e implicitly pass the self parameter) instead of a function?

Answer 1

This will work. But I’m not sure if this is what you are looking for

class Foo(object):                                                          
  def __init__(self):                                                 
    def f(a,self,b):                                            
      print a+b                                           
    self.g = functools.partial(f,1, self) # <= passing `self` also.

x = Foo()
x.g(2)