[PyQt] 'import PyQt4.uic.Compiler' fails with Python 3.2

[Arfrever Frehtes Taifersar Arahesis]

2010-09-23 18:22:20 Phil Thompson napisał(a):
> On Wed, 22 Sep 2010 16:16:05 +0200, Arfrever Frehtes Taifersar Arahesis
> <arfrever.fta at gmail.com> wrote:
> > 2010-09-19 22:58:26 Phil Thompson napisał(a):
> >> On Sun, 19 Sep 2010 22:55:17 +0200, Arfrever Frehtes Taifersar Arahesis
> >> <arfrever.fta at gmail.com> wrote:
> >> > 2010-09-19 15:24:53 Phil Thompson napisał(a):
> >> >> On Fri, 17 Sep 2010 20:51:55 +0200, Arfrever Frehtes Taifersar
> >> >> Arahesis
> >> >> <arfrever.fta at gmail.com> wrote:
> >> >> > I use SIP 4.11.1 and PyQt4 4.7.6.
> >> >> > 
> >> >> > $ python3.1 -c 'import PyQt4.uic.Compiler'
> >> >> > $ python3.2 -c 'import PyQt4.uic.Compiler'
> >> >> > Traceback (most recent call last):
> >> >> >   File
> >> >> >  
> >> "/usr/lib64/python3.2/site-packages/PyQt4/uic/Compiler/proxy_type.py",
> >> >> >   line 16, in __getattribute__
> >> >> >     return type.__getattribute__(cls, name)
> >> >> > AttributeError: type object 'ProxyBase' has no attribute 'module'
> >> >> > 
> >> >> > During handling of the above exception, another exception
> occurred:
> >> >> > 
> >> >> > Traceback (most recent call last):
> >> >> >   File "<string>", line 1, in <module>
> >> >> >   File "/usr/lib64/python3.2/site-packages/PyQt4/uic/__init__.py",
> >> line
> >> >> 3,
> >> >> >   in <module>
> >> >> >     from PyQt4.uic.Compiler import indenter, compiler
> >> >> >   File
> >> >> >  
> >> "/usr/lib64/python3.2/site-packages/PyQt4/uic/Compiler/compiler.py",
> >> >> line
> >> >> >   5, in <module>
> >> >> >     from PyQt4.uic.Compiler import qtproxies
> >> >> >   File
> >> >> >  
> >> "/usr/lib64/python3.2/site-packages/PyQt4/uic/Compiler/qtproxies.py",
> >> >> >   line 8, in <module>
> >> >> >     from PyQt4.uic.port_v3.proxy_base import ProxyBase
> >> >> >   File
> >> >> >  
> >> "/usr/lib64/python3.2/site-packages/PyQt4/uic/port_v3/proxy_base.py",
> >> >> >   line 4, in <module>
> >> >> >     class ProxyBase(metaclass=ProxyType):
> >> >> >   File
> >> >> >  
> >> "/usr/lib64/python3.2/site-packages/PyQt4/uic/Compiler/proxy_type.py",
> >> >> >   line 11, in __init__
> >> >> >     if not hasattr(args[0], "module"):
> >> >> >   File
> >> >> >  
> >> "/usr/lib64/python3.2/site-packages/PyQt4/uic/Compiler/proxy_type.py",
> >> >> >   line 19, in __getattribute__
> >> >> >     from PyQt4.uic.Compiler.qtproxies import LiteralProxyClass
> >> >> > ImportError: cannot import name LiteralProxyClass
> >> >> 
> >> >> This looks like a Python 3.2a2 bug.
> >> > 
> >> > If it's really a bug in Python, and not another intentional,
> >> incompatible
> >> > change,
> >> > then could you report it to http://bugs.python.org/ ?
> >> > (I use snapshots of Python, updated at least once per week, not
> 3.2a2.)
> >> 
> >> It disappears if you add a str(cls) just before the import statement
> >> which
> >> suggests it's a bug rather than a change. However I don't have enough
> >> information to put together a proper bug report.
> > 
> > It's not a bug in Python 3.2 :) .
> > 
> > http://docs.python.org/dev/py3k/whatsnew/3.2.html:
> > "The hasattr() function used to catch and suppress any Exception.
> > Now, it only catches AttributeError. Under the hood, hasattr() works
> > by calling getattr() and throwing away the results. This is necessary
> > because dynamic attribute creation is possible using __getattribute__()
> > or __getattr__(). If hasattr() were to just scan instance and class
> > dictionaries it would miss the dynamic methods and make it difficult
> > to implement proxy objects."
> > 
> > The attached patch changes ImportError into AttributeError, which fixes
> > 'import PyQt4.uic.Compiler'.
> 
> This doesn't explain the problem...
> 
> - the import of the qtproxies module shouldn't fail so wrapping it in
> try/except shouldn't make any difference

I don't know why 'from PyQt4.uic.Compiler.qtproxies import LiteralProxyClass'
initially fails, but it also fails with Python 2.6, 2.7 and 3.1.

You can apply the following patch to see this behavior:

--- pyuic/uic/Compiler/proxy_type.py
+++ pyuic/uic/Compiler/proxy_type.py
@@ -16,7 +16,12 @@
             return type.__getattribute__(cls, name)
         except AttributeError:
             # Avoid a circular import.
-            from PyQt4.uic.Compiler.qtproxies import LiteralProxyClass
+            try:
+                from PyQt4.uic.Compiler.qtproxies import LiteralProxyClass
+                print("'from PyQt4.uic.Compiler.qtproxies import LiteralProxyClass' succeeded")
+            except ImportError:
+                print("'from PyQt4.uic.Compiler.qtproxies import LiteralProxyClass' failed")
+                raise
 
             return type(name, (LiteralProxyClass, ),
                         {"module": moduleMember(type.__getattribute__(cls, "module"),

Try to import PyQt4.uic.Compiler after applying this patch.

> - if Python is no longer suppressing certain exceptions then you would
> expect to see new exceptions raised, not a segfault

I see exceptions, not a segmentation fault.

> - if adding a call to str(), which shouldn't have any side effects, avoids
> the segfault then that implies a memory corruption problem.

str(x) calls x.__str__(), which can have side effects.

-- 
Arfrever Frehtes Taifersar Arahesis
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