about 'setattr(o, name, value)' and 'inspect.signature(f)'

[Terry Reedy]

On 10/10/2017 10:37 AM, xieyuheng wrote:

> 2. what kind of functions does not have signature,
>     so that 'inspect.signature(f)' can be used for them ?

When .signature was added, it may not have been usable with *any* 
C-coded function.  About the same, a mechanism was added to make 
signatures available with C-coded functions.  Using the mechanism 
requires recoding for each file.  By now, many CPython functions have 
been recoded.

>     section '29.12.3. Introspecting callables with the Signature object'
>     of the official documentation says :
> 
>     > Some callables may not be introspectable in certain implementations of Python.

So 'some' is a gradually shrinking set.

>     > For example, in CPython, some built-in functions defined in C
>     > provide no metadata about their arguments.
> 
>     this is depends on implementation, so I ask for CPython.

-- 
Terry Jan Reedy