custom print statement for python function objects

functional-programming, python

Solution

Few errors:

>>> def f():
...     pass
... 
>>> g = f()     <---- g is the return value of running f
>>> print g
None

in the first case, when you call print, you are calling a string representation of f

>>> f = F()
>>> print f    <----- f is an instance of class F and 
               <----- print f tries to provide a suitable string representation
               <----- by calling f.__str__

You should use doc strings for your motives

>>> def f():
...     " some doc"
...     pass
... 
>>> 
>>> f.__doc__
' some doc'
>>>

What you are trying to do is override the method wrapper `__str__`.

>>> def f():
...     "some documentation .."
...     pass
... 
>>> 
>>> f.__str__
<method-wrapper '__str__' of function object at 0x100430140>
>>>

Problem

I know that if I write a class, I can definite a custom print function as below. ``` >>> class F: ... def __str__(self): ... return 'This describes the data of F.' ... >>> f = F() >>> print f This describes the data of F. ``` But, what if I want to do the same for a function object? For example, ``` >>> def f(): ... pass ... >>> g = f >>> print g <function f at 0x7f738d6da5f0> ``` Instead of '<function f at 0x7f738d6da5f0>', I'd like to somehow specify what was printed. The motivation for doing this is that I'm going to store a bunch of function objects in a list, and I'd like to iterate over the list and print human-readable descriptions of the types of functions without adding additional complexity, e.g., tuples of function objects and strings. Thanks in advance for any help you can provide. Edit: I changed my example to reflect what I was trying to convey, unfortunately I typed 'f()' when I meant 'f'. I am interested in a custom label for the function object, not customizing the return (which it is obvious how to do). Sorry for any confusion this has caused.

Original source