One of the nice features of 3.0 is that differences between classes
defined in C and Python (other than speed) are mostly erased or hidden
from the view of a Python programmer.
However, there are still sometimes surprising and quite visible
differences between 'functions' written in C and Python. Can these be
better unified also?
In particular, built-in functions, in spite of of being labeled
'builtin_function_or_method', are not usable as methods because they
lack the __get__ method needed to bind function to instance.
[Q. Any reason to not shorten that to 'built-in function'?]
So, as a c.l.p poster discovered, within a class statement,
__hash__ = lambda x: id(x) # works, while the apparently cleaner
__hash__ = id # raises TypeError: id() takes exactly one argument (0 given)
[Irony: trivial lambda wrapping, lambda x: f(x) has been described here
as useless and diseased, but is seems that casting 'built-in function'
to 'function' is not so completely useless. ;-]
In this case, __hash__ = object.__hash__ is available, as is
object.__repr__, but this is not true in general for C functions.
The difference between a C function and a C method wrapper is
tantalizingly small:
>>> i = set(dir(id))
>>> h = set(dir(object.__hash__))
>>> i-h
{'__module__', '__self__'}
>>> h-i
{'__objclass__', '__get__'}
Similarly, for
>>> def f(): pass
>>> ff = set(dir(f))
>>> ff - i
{'__defaults__', '__annotations__', '__kwdefaults__', '__globals__',
'__closure__', '__dict__', '__code__', '__get__'}
the only un-obvious difference is __get__,
So I cannot help but wonder: is this is essential? or could it be
removed but has not yet? Could the object wrapper for C functions get a
__get__ method so they become methods when accessed via a class just
like Python functions do?
Terry Jan Reedy
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