En Wed, 28 Sep 2011 18:51:00 -0300, Chris Kaynor
<ckay...@zindagigames.com> escribió:
On Wed, Sep 28, 2011 at 2:37 PM, Arnaud Delobelle <arno...@gmail.com>
wrote:
On 28 September 2011 22:26, Ethan Furman <et...@stoneleaf.us> wrote:
I remember that 'class' is sugar for type(....).
I don't remember if 'def' is sugar for something besides lambda.
Any clues for me? Heck, I'll even be grateful for outright answers!
It's not really sugar. But I think you mean something like this:
class A: pass
...
type(A)
<class 'type'>
type is type(A)
True
So the closest you get for functions will be:
def f(): pass
...
type(f)
<class 'function'>
Try help(type(f)) to see how to use it to create a function object.
The problem is that you need to provide a code object, and the easiest
way to create a code object is to use a def statement :)
I would say compile isn't too much harder to use:
c = compile('a = 123', 'test', 'exec')
d = {}
f = types.FunctionType(c, d, 'test')
f()
print d
{'a': 123}
Although it appears you get all of the variables defined as global
apparently (try "f = types.FunctionType(c, globals(), 'test')"
instead).
I know no way of compiling a function body alone. Suppose you have this
function:
def foo(x):
print x
y = 2*x
return y
py> compile(" print x\n y = 2*x\n return y", "<string>", "exec")
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<string>", line 1
print x
^
IndentationError: unexpected indent
py> compile("print x\ny = 2*x\nreturn y", "<string>", "exec")
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<string>", line 3
SyntaxError: 'return' outside function
If you include the 'def' statement in the source string, the resulting
code object does not represent the function itself, but a "module"
defining it:
py> f = FunctionType(compile("def foo(x):\n print x\n y = 2*x\n return
y\n",
... "<string>", "exec"), globals(), "foo")
py> f(3)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: <module>() takes no arguments (1 given)
py> dis.dis(f)
1 0 LOAD_CONST 0 (<code object foo at 00C0FAD0,
file "<string>", line 1>)
3 MAKE_FUNCTION 0
6 STORE_NAME 0 (foo)
9 LOAD_CONST 1 (None)
12 RETURN_VALUE
To get at the actual function code, one should use
f.func_code.co_consts[0]; this would be the 'code' parameter for
types.FunctionType. Very complicated, really; nothing can beat the 'def'
statement for defining a function ;)
--
Gabriel Genellina
--
http://mail.python.org/mailman/listinfo/python-list
