Function argument conformity check

[dlists.cad@gmail.com]

Hi. I am looking for a way to check if some given set of (*args,
**kwds) conforms to the argument specification of a given function,
without calling that function.

For example, given the function foo:
def foo(a, b, c): pass

and some tuple args and some dict kwds, is there a way to tell if i
_could_ call foo(*args, **kwds) without getting an exception for those
arguments? I am hoping there is a way to do this without actually
writing out the argument logic python uses.

Thanks.

[=?iso-8859-1?q?C=E9dric_Lucantis?=]

Re: Function argument conformity check

Hi,

Le Wednesday 18 June 2008 20:19:12 dlists.cad@gmai l.com, vous avez écrit :

Hi. I am looking for a way to check if some given set of (*args,
**kwds) conforms to the argument specification of a given function,
without calling that function.
>
For example, given the function foo:
def foo(a, b, c): pass
>
and some tuple args and some dict kwds, is there a way to tell if i
_could_ call foo(*args, **kwds) without getting an exception for those
arguments? I am hoping there is a way to do this without actually
writing out the argument logic python uses.
>

Each function object is associated to a code object which you can get with
foo.func_code. Two of this object's attributes will help you: co_argcount and
co_varnames. The first is the number of arguments of the function, and the
second a list of all the local variables names, including the arguments
(which are always the first items of the list). When some arguments have
default values, they are stored in foo.func_defaul ts (and these arguments are
always after non-default args in the co_argnames list).

Finally, it seems that some flags are set in code.co_flags if the function
accepts varargs like *args, **kwargs, but I don't know where these are
defined.

Note that I never found any doc about that and merely guessed it by playing
with func objects, so consider all this possibly wrong or subject to change.

--
Cédric Lucantis

[dlists.cad@gmail.com]

Re: Function argument conformity check

On Jun 18, 3:13 pm, Cédric Lucantis <o...@no-log.orgwrote:

Hi,
>
Le Wednesday 18 June 2008 20:19:12 dlists....@gmai l.com, vous avez écrit :
>

Hi. I am looking for a way to check if some given set of (*args,
**kwds) conforms to the argument specification of a given function,
without calling that function.

>

For example, given the function foo:
def foo(a, b, c): pass

>

and some tuple args and some dict kwds, is there a way to tell if i
_could_ call foo(*args, **kwds) without getting an exception for those
arguments? I am hoping there is a way to do this without actually
writing out the argument logic python uses.

>
Each function object is associated to a code object which you can get with
foo.func_code. Two of this object's attributes will help you: co_argcountand
co_varnames. The first is the number of arguments of the function, and the
second a list of all the local variables names, including the arguments
(which are always the first items of the list). When some arguments have
default values, they are stored in foo.func_defaul ts (and these argumentsare
always after non-default args in the co_argnames list).
>
Finally, it seems that some flags are set in code.co_flags if the function
accepts varargs like *args, **kwargs, but I don't know where these are
defined.
>
Note that I never found any doc about that and merely guessed it by playing
with func objects, so consider all this possibly wrong or subject to change.
>
--
Cédric Lucantis

I am aware of these attributes, although you can get them all in a
more organized form using the getfullargspec function in the inspect
module from the standard library.

The problem is that using these attributes, I would essentially have
to re-write the logic python uses when calling a function with a given
set of arguments. I was hoping there is a way to get at that logic
without rewriting it.

[Matthew Woodcraft]

Re: Function argument conformity check

In article <9577cf2e-4440-4d97-b8e8-1dbc00bfca68@34 g2000hsh.google groups.com>,

The problem is that using these attributes, I would essentially have
to re-write the logic python uses when calling a function with a
given set of arguments. I was hoping there is a way to get at that
logic without rewriting it.

I don't think there is. I ended up rewriting it when I wanted to do a
similar thing.

-M-

[George Sakkis]

Re: Function argument conformity check

On Jun 18, 3:41 pm, dlists....@gmai l.com wrote:

On Jun 18, 3:13 pm, Cédric Lucantis <o...@no-log.orgwrote:
>
>
>

Hi,

>

Le Wednesday 18 June 2008 20:19:12 dlists....@gmai l.com, vous avez écrit :

>

Hi. I am looking for a way to check if some given set of (*args,
**kwds) conforms to the argument specification of a given function,
without calling that function.

>

For example, given the function foo:
def foo(a, b, c): pass

>

and some tuple args and some dict kwds, is there a way to tell if i
_could_ call foo(*args, **kwds) without getting an exception for those
arguments? I am hoping there is a way to do this without actually
writing out the argument logic python uses.

>

Each function object is associated to a code object which you can get with
foo.func_code. Two of this object's attributes will help you: co_argcount and
co_varnames. The first is the number of arguments of the function, and the
second a list of all the local variables names, including the arguments
(which are always the first items of the list). When some arguments have
default values, they are stored in foo.func_defaul ts (and these arguments are
always after non-default args in the co_argnames list).

>

Finally, it seems that some flags are set in code.co_flags if the function
accepts varargs like *args, **kwargs, but I don't know where these are
defined.

>

Note that I never found any doc about that and merely guessed it by playing
with func objects, so consider all this possibly wrong or subject to change.

>

--
Cédric Lucantis

>
I am aware of these attributes, although you can get them all in a
more organized form using the getfullargspec function in the inspect
module from the standard library.
>
The problem is that using these attributes, I would essentially have
to re-write the logic python uses when calling a function with a given
set of arguments. I was hoping there is a way to get at that logic
without rewriting it.

Sure; copy it from someone that has already done it ;-)

http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/551779

HTH,
George

[crazychimp132@gmail.com]

Re: Function argument conformity check

On Jun 18, 5:05 pm, George Sakkis <george.sak...@ gmail.comwrote:

On Jun 18, 3:41 pm, dlists....@gmai l.com wrote:
>
>
>

On Jun 18, 3:13 pm, Cédric Lucantis <o...@no-log.orgwrote:

>

Hi,

>

Le Wednesday 18 June 2008 20:19:12 dlists....@gmai l.com, vous avez écrit :

>

Hi. I am looking for a way to check if some given set of (*args,
**kwds) conforms to the argument specification of a given function,
without calling that function.

>

For example, given the function foo:
def foo(a, b, c): pass

>

and some tuple args and some dict kwds, is there a way to tell if i
_could_ call foo(*args, **kwds) without getting an exception for those
arguments? I am hoping there is a way to do this without actually
writing out the argument logic python uses.

>

Each function object is associated to a code object which you can getwith
foo.func_code. Two of this object's attributes will help you: co_argcount and
co_varnames. The first is the number of arguments of the function, and the
second a list of all the local variables names, including the arguments
(which are always the first items of the list). When some arguments have
default values, they are stored in foo.func_defaul ts (and these arguments are
always after non-default args in the co_argnames list).

>

Finally, it seems that some flags are set in code.co_flags if the function
accepts varargs like *args, **kwargs, but I don't know where these are
defined.

>

Note that I never found any doc about that and merely guessed it by playing
with func objects, so consider all this possibly wrong or subject to change.

>

--
Cédric Lucantis

>

I am aware of these attributes, although you can get them all in a
more organized form using the getfullargspec function in the inspect
module from the standard library.

>

The problem is that using these attributes, I would essentially have
to re-write the logic python uses when calling a function with a given
set of arguments. I was hoping there is a way to get at that logic
without rewriting it.

>
Sure; copy it from someone that has already done it ;-)
>

http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/551779

>
HTH,
George

This is exactly what I was looking for- thanks!

[Bruno Desthuilliers]

Re: Function argument conformity check

dlists.cad@gmai l.com a écrit :

Hi. I am looking for a way to check if some given set of (*args,
**kwds) conforms to the argument specification of a given function,
without calling that function.

import inspect
help(inspect.ge targspec)