introspection and functions

[Bruno Desthuilliers]

yagyala a écrit :

Hi. I would like to be able to tell, at run time, how many parameters
a function requires. Ideally I would like to be able to tell which are
optional as well. I've tried looking at the functions attributes, but
haven't found one that helps in this. How can I do this?

(['arg1', 'arg2', 'arg3'], 'args', 'kw', ('toto',))


HTH

 

[yagyala]

Hi. I would like to be able to tell, at run time, how many parameters
a function requires. Ideally I would like to be able to tell which are
optional as well. I've tried looking at the functions attributes, but
haven't found one that helps in this. How can I do this?

Thanks

 

[Wildemar Wildenburger]

Hi. I would like to be able to tell, at run time, how many parameters
a function requires. Ideally I would like to be able to tell which are
optional as well. I've tried looking at the functions attributes, but
haven't found one that helps in this. How can I do this?

I've never used it before, but there is the "inspect" module.
<url:http://docs.python.org/lib/module-inspect.html>.
That any good?

/W

 

[James Stroud]

Hi. I would like to be able to tell, at run time, how many parameters
a function requires. Ideally I would like to be able to tell which are
optional as well. I've tried looking at the functions attributes, but
haven't found one that helps in this. How can I do this?

Thanks

py> def doit(a, b, c, x=14):
.... pass
....
py> doit.func_code.co_argcount
4
py> doit.func_code.co_varnames
('a', 'b', 'c', 'x')
py> doit.func_defaults
(14,)

James

 

[Scott David Daniels]

Hi. I would like to be able to tell, at run time, how many parameters
a function requires. Ideally I would like to be able to tell which are
optional as well. I've tried looking at the functions attributes, but
haven't found one that helps in this. How can I do this?

Thanks

This really only will work for those functions that are simply
constructed. You are better off not trying to do this, or code
like the following will confound your code:

from functools import partial

def somefunction(a=23, b=14, c='hi'):
print 'Finally'

f = partial(somefunction, b=13)
g = partial(f, a=19)
h = partial(g, c=123)
print whatargs(h)

 

[Ayaz Ahmed Khan]

"James Stroud" typed:

py> def doit(a, b, c, x=14):
... pass
...
py> doit.func_code.co_argcount
4
py> doit.func_code.co_varnames
('a', 'b', 'c', 'x')
py> doit.func_defaults
(14,)

Neat.

 

[=?ISO-8859-1?Q?Ricardo_Ar=E1oz?=]

"James Stroud" typed:

Neat.

How do you know the 14 corresponds to x ?

 

[Wildemar Wildenburger]

How do you know the 14 corresponds to x ?

Well, there is one optional argument (len(doit.func_defaults)==1) and
those *must* come after mendatory arguments. More generally: If a
function has n optional args, they're the n last ones. There is never
any ambiguity.

/W