On 3/7/2014 3:10 PM, Jurko Gospodnetić wrote:
Hi.
I just noticed that the way help() function displays a function
signature changed between Python 3.3 & 3.4 but I can not find this
documented anywhere. Here's a matching example in both Python 3.3 &
Python 3.4 for comparison:
----------------------------------------
Python 3.3.3 (v3.3.3:c3896275c0f6, Nov 18 2013, 21:19:30) [MSC v.1600
64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
def f(a, b, c):
... print(a, b, c)
...
def g(*args, **kwargs):
... f(*args, **kwargs)
...
import inspect
print(inspect.signature(f))
(a, b, c)
print(inspect.signature(g))
(*args, **kwargs)
g.__wrapped__ = f
print(inspect.signature(f))
(a, b, c)
print(inspect.signature(g))
(a, b, c)
help(f)
Help on function f in module __main__:
f(a, b, c)
help(g)
Help on function g in module __main__:
g(*args, **kwargs)
----------------------------------------
Python 3.4.0b3 (v3.4.0b3:a97ce3ecc96a, Jan 26 2014, 17:50:55) [MSC
v.1600 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
def f(a, b, c):
... print(a, b, c)
...
def g(*args, **kwargs):
... f(*args, **kwargs)
...
import inspect
print(inspect.signature(f))
(a, b, c)
print(inspect.signature(g))
(*args, **kwargs)
g.__wrapped__ = f
print(inspect.signature(f))
(a, b, c)
print(inspect.signature(g))
(a, b, c)
help(f)
Help on function f in module __main__:
f(a, b, c)
help(g)
Help on function g in module __main__:
g(a, b, c)
----------------------------------------
As you can see by comparing those two outputs, setting the __wrapped__
attribute on a wrapper function affects the inspect.signature() results
on that function. This behaviour is the same in both Python 3.3. & 3.4
and is (somewhat) described in the Python documentation.
I suspect that is it intentional that the output of help is not exactly
defined, just as exception messages are not. We consider either fair
game to be changed in new versions.
However, help() output is not affected by this in Python 3.3,
That was a bug.
but is
affected in Python 3.4, and I can not find anything regarding this in
the Python 3.4 docs.
Assuming that pydoc (and hence help()) have not (yet?) been switched to
using .signature directly, I suspect this is a side-effect of
http://bugs.python.org/issue17481
inspect.getfullargspec should use __signature__
Can something related to this be added at least to the 'what's changed'
docs, if not to the help() documentation as well?
Perhaps add something to
Other Language Changes
----------------------
* Signatures reported by help() have been modified and improved by
Argument Clinic and changes to the inspect module.
--
Terry Jan Reedy
_______________________________________________
Python-Dev mailing list
Python-Dev@python.org
https://mail.python.org/mailman/listinfo/python-dev
Unsubscribe:
https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
