Eric Snow wrote:
> In Python, three types of objects have special syntax and mechanics
> for their instantiation, during which a code object is generated:
> modules, classes, and functions.
I believe you are labouring under a misapprehension. Modules and classes
don't generate code objects.
The simplest possible module just has a name:
>>> import sys
>>> module = type(sys)
>>> module("name")
<module 'name' (built-in)>
Or if you prefer to do it the "normal" way by importing from source code,
the simplest source code of all is just an empty file.
A module is an object with a __dict__, a __name__, and a __docstring__ which
defaults to None. That's it. No code objects, unless you populate the
__dict__ with functions, but it is the *functions* that have the code
objects, not the module itself. The module is just a container.
Classes are similar. The simplest class:
class K:
pass
or if you prefer:
>>> type('K', (), {})
<class '__main__.K'>
Again, no code objects unless you populate the dict with functions (which
get turned into methods). Again, the class object is just a container. A
more complex container than modules, with a richer set of inherited
behaviour, but still just a container.
The signature for creating a function is very different:
help(type(lambda: None)) =>
class function(object)
| function(code, globals[, name[, argdefs[, closure]]])
|
| Create a function object from a code object and a dictionary.
| The optional name string overrides the name from the code object.
| The optional argdefs tuple specifies the default argument values.
| The optional closure tuple supplies the bindings for free variables.
The simplest function I can think of:
>>> co = compile('pass', '', 'single')
>>> f = type(lambda: None)(co, {})
Even simpler than
def f():
pass
Can you see why?
If you inspect a function object, you will see that it always has a code
object, even if the code object does nothing but return None:
>>> import dis
>>> dis.dis(f.func_code)
1 0 LOAD_CONST 0 (None)
3 RETURN_VALUE
There may be some other obscure built-in type that includes code objects,
but I can't imagine what it would be. I feel confident in saying that
functions, and functions alone, contain code. Even methods are just
wrappers around functions. Even built-in functions like len don't contain
code! (Or at least, their code isn't accessible from Python.) Which makes
sense, if you think about it: their code is part of the Python virtual
machine, not the object.
--
Steven
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