[Python-projects] Problem and Fix for PyQt4 and pylint

[Sylvain Thénault]

On 27 juillet 18:53, Derek Harland wrote:
> Hello,

Hi,
 
> The more recent releases of PyQt4 seem to break pylint ... pylint
> will emit the following errors
> (i) unable to find submodules of PyQt4
>     main.py:3: [E0611] No name 'QtCore' in module 'PyQt4'
>     main.py:4: [E0611] No name 'QtGui' in module 'PyQt4'
> (ii) as a result, all use of classes from eg QtGui, or inheritors
> from them, spark lots of errors
>     main.py:11: [E1101, MyValidator] Module 'PyQt4.QtGui2' has no
> 'QValidator' member
>     main.py:33: [E1101, DaycountWidget.__init__] Instance of
> 'DaycountWidget' has no 'setEditable' member
> 
> I've tracked down the problem I believe ...
> * PyQt4.QtCore's namespace has instances of a c-module defined type
> called pyqtSignal
> * pylint believes these are methoddescriptors
> [inspect.ismethoddescriptor(.) -> returns true ]
> * However, they do not have __name__ or __doc__ defined, which
> logilab/astng/raw_building.py:object_build_methoddescriptor expects

even if having a fix for this on the pylint/astng side, this is probably
worth mentionning to the pyqt team.
 
> As a result pylint basically refuses to load the Qt modules and this
> causes all subsequent errors.
> 
> How to fix?  The following patch will avoid the error

which error ? False positives as mentioned above ?
 
> --- logilab/astng/builder.py.orig	2009-07-27 18:43:54.000000000 +1200
> +++ logilab/astng/builder.py	2009-07-27 18:44:57.000000000 +1200
> @@ -194,8 +194,12 @@
>                      # recursion
>                      self.object_build(class_node, member)
>              elif ismethoddescriptor(member):
> -                assert isinstance(member, object)
> -                object_build_methoddescriptor(node, member)
> +                # avoid objects without __name__, they're not what
> they seem ...
> +                # (eg PyQt4.QtCore.pyqtSignal instances)
> +                if hasattr(member, "__name__") and hasattr(member,
> "__doc__"):
> +                    assert isinstance(member, object)
> +                    object_build_methoddescriptor(node, member)
> +                else: attach_dummy_node(node, name, member)
>              elif isdatadescriptor(member):
>                  assert isinstance(member, object)
>                  object_build_datadescriptor(node, member, name)

could you provide which version of pyqt are you using and a minimal
sample script to reproduce the pb ?

imo (but I've not at all tracked down this as you have), a better fix
consits in giving to object_build_* methods the name of the member
(eg the loop variable) if member.__name__ is not set.

> After this patch pylint seems to work as expected.  However users
> must ensure their code imports PyQt4.QtGui before PyQt4.QtCore or a
> bus error will occur when running pylint. (I have no idea why ...
> within a python program itself it doesn't mind the order in which
> they are imported).

Weird
 
> Hope this is useful, I know that there are a few posts to newsgroups
> wondering how to fix this problem

Bug reports, moreover those including results of digging the code, are
really valuable! Thank you for this one.

-- 
Sylvain Thénault                               LOGILAB, Paris (France)
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