Re: [ctypes-users] Prototypes with c_double

[Lenard L. <le...@te...>]

Nicholas wrote:
> Hi,
>
> Im not sure if this is a bug or something I dont understand.
> import ctypes as c
> libc = c.cdll.msvcrt
> proto = c.CFUNCTYPE(c.c_double, c.c_double)
The CFUNCTYPE is for wrapping a Python callable in C function for use as 
a C callback.

> floor=proto(libc.floor)
> floor(4.5)
>
> Traceback (most recent call last):
>   File "\loewis\25\python\Modules\_ctypes\callbacks.c", line 206, in 
> 'calling callback function'
> ctypes.ArgumentError: argument 1: <type 'exceptions.TypeError'>: Don't 
> know how to convert parameter 1
>
> This however works fine:
> floor=libc.floor
> floor.argtypes=c.c_double,
floor.argtypes=[c.c_double]   # argtypes is plural an so takes a list.
> floor.restype = c.c_double
> floor(5.6)
> 5.0
>
This is the correct way to assign argument and return types to an 
foreign C function.

-- 
Lenard Lindstrom
<le...@te...>