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

[Derek Harland]

Hi Sylvain

* First up, I should point out that I think pylint is a great tool ...  
I use it in combination with flymake in emacs to give me realtime  
error checking which is very helpful.
* I have already posted the suggested fix to the PyQt mailing list,  
along with the note of a bus error
* On the bus error I have more information but will post that separately
* As request, attached is an example simple PyQt app.  Here is what  
the unpatched pylint output appears as

$ pylint-2.6 -f parseable -r n --disable-msg-cat=C,R testcase.py
testcase.py:9: [E0611] No name 'QtGui' in module 'PyQt4'
testcase.py:9: [E0611] No name 'QtCore' in module 'PyQt4'
testcase.py:11: [W0232, TextWidget] Class has no __init__ method
testcase.py:11: [E1101, TextWidget] Module 'PyQt4.QtGui' has no  
'QLineEdit' member
testcase.py:14: [E1101, MainWindow] Module 'PyQt4.QtGui' has no  
'QDialog' member
testcase.py:16: [E1101, MainWindow.__init__] Module 'PyQt4.QtGui' has  
no 'QDialog' member
testcase.py:21: [E1101, MainWindow.init] Module 'PyQt4.QtGui' has no  
'QGroupBox' member
testcase.py:22: [E1101, MainWindow.init] Module 'PyQt4.QtGui' has no  
'QRadioButton' member
testcase.py:23: [E1101, MainWindow.init] Module 'PyQt4.QtGui' has no  
'QRadioButton' member
testcase.py:24: [E1101, MainWindow.init] Module 'PyQt4.QtGui' has no  
'QRadioButton' member
testcase.py:27: [E1101, MainWindow.init] Module 'PyQt4.QtGui' has no  
'QVBoxLayout' member
testcase.py:35: [E1101, MainWindow.init] Module 'PyQt4.QtGui' has no  
'QVBoxLayout' member
testcase.py:38: [E1101, MainWindow.init] Instance of 'TextWidget' has  
no 'setEnabled' member
testcase.py:42: [E1101, MainWindow.init] Module 'PyQt4.QtGui' has no  
'QPushButton' member
testcase.py:45: [E1101, MainWindow.init] Instance of 'MainWindow' has  
no 'setLayout' member
testcase.py:48: [E1101, MainWindow.quit] Instance of 'MainWindow' has  
no 'done' member
testcase.py:47: [W0613, MainWindow.quit] Unused argument 'args'
testcase.py:47: [W0613, MainWindow.quit] Unused argument 'kw'
testcase.py:51: [E1101] Module 'PyQt4.QtGui' has no 'QApplication'  
member
testcase.py:53: [E1101] Instance of 'MainWindow' has no 'exec_' member
testcase.py:9: [W0611] Unused import QtCore

Its mostly full of false positives.  A largish module using Qt gets  
swamped with output, and in my case it means emacs highlights every  
other line as containing a problem :-)

With the patch it appears as

$ pylint-2.6 -f parseable -r n --disable-msg-cat=C,R testcase.py
testcase.py:47: [W0613, MainWindow.quit] Unused argument 'args'
testcase.py:47: [W0613, MainWindow.quit] Unused argument 'kw'
testcase.py:9: [W0611] Unused import QtCore

Pleased to (hopefully) help.
derek.

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On 29/07/2009, at 12:37 AM, Sylvain Th?nault wrote:

> 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 Th?nault                               LOGILAB, Paris (France)
> Formations Python, Debian, M?th. Agiles: http://www.logilab.fr/formations
> D?veloppement logiciel sur mesure:       http://www.logilab.fr/ 
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