introspecting builtin functions/methods

[Gonçalo Rodrigues]

Hi,

Does anyone know if and how I can, from within Python, read the
signatures of builtin methods/functions?

The following fails:

import inspect
inspect.getargspec(list.append) Traceback (most recent call last):
File "<interactive input>", line 1, in ?
File "C:\Python23\lib\inspect.py", line 655, in getargspec
raise TypeError('arg is not a Python function')
TypeError: arg is not a Python function inspect.getargspec(list.append.__call__) Traceback (most recent call last):
File "<interactive input>", line 1, in ?
File "C:\Python23\lib\inspect.py", line 655, in getargspec
raise TypeError('arg is not a Python function')
TypeError: arg is not a Python function

Also:
for elem in dir(list.append):

.... print elem
....
__call__
__class__
__delattr__
__doc__
__get__
__getattribute__
__hash__
__init__
__name__
__new__
__objclass__
__reduce__
__reduce_ex__
__repr__
__setattr__
__str__

gives no clue.

TIA, with my best regards,
G. Rodrigues

[Jp Calderone]

On Tue, Dec 16, 2003 at 03:56:45PM +0000, Gon?alo Rodrigues wrote:

Hi,

Does anyone know if and how I can, from within Python, read the
signatures of builtin methods/functions?

The signatures for builtins are not available via any of the normal
introspection routines. The way argument parsing works in C makes it so
that the expected arguments are not available anywhere (typically) except as
a string literal inside the function definition.

It would be pretty handy if this information was available, but I think
converting the existing code to make it available would be a herculean
effort.

Jp

[Fredrik Lundh]

Gonçalo Rodrigues wrote:

Does anyone know if and how I can, from within Python, read the
signatures of builtin methods/functions?

For methods/functions written in C, the signature is defined by a
string passed to an internal C function (ParseTuple). And functions
don't even have to use that function to process their arguments;
they can pull values right out of the argument tuple (or they can
use ParseTuple more than once, in order to support multiple calling
conventions).

I'd say your only hope is the doc string:

inspect.getdoc(list.append)

'L.append(object) -- append object to end'

</F>

[Martin Franklin]

On Tue, 2003-12-16 at 15:56, =?UNKNOWN?Q?Gon=E7alo?= Rodrigues wrote:

Hi,

Does anyone know if and how I can, from within Python, read the
signatures of builtin methods/functions?

The following fails:

import inspect
inspect.getargspec(list.append) Traceback (most recent call last):
File "<interactive input>", line 1, in ?
File "C:\Python23\lib\inspect.py", line 655, in getargspec
raise TypeError('arg is not a Python function')
TypeError: arg is not a Python function inspect.getargspec(list.append.__call__) Traceback (most recent call last):
File "<interactive input>", line 1, in ?
File "C:\Python23\lib\inspect.py", line 655, in getargspec
raise TypeError('arg is not a Python function')
TypeError: arg is not a Python function

Also:
for elem in dir(list.append): ... print elem
...
__call__
__class__
__delattr__
__doc__
__get__
__getattribute__
__hash__
__init__
__name__
__new__
__objclass__
__reduce__
__reduce_ex__
__repr__
__setattr__
__str__

gives no clue.

TIA, with my best regards,
G. Rodrigues

You mean something like:

list.append.__doc__ 'L.append(object) -- append object to end' list.count.__doc__

'L.count(value) -> integer -- return number of occurrences of value'

--
Martin Franklin <mf********@gatwick.westerngeco.slb.com>