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Details

Type: Bug
Resolution: Done
Priority: P2: Important
Fix Version/s: 6.0
Affects Version/s: 1.2.x, 5.11.0
Component/s: PySide
Labels:
- PreTP
- harder
Environment:
Ubuntu 12.04 x64 with Python 3.4.0 x64 running PySide 1.2.2 installed via pip 1.5.6. I had previously seen the problem with Python 3.3.5 and PySide 1.2.1 using the attached "enum.py" and upgraded in hopes that it would be fixed.

Commits:
4f1739e062623d3ab8aebe9540e945464734a75b (pyside/pyside-setup/5.14)

Description

When attempting to use the new Python 3.4.0 "enum.Enum", I encounter multiple problems.

Consider the following PY file:

pysideEnumBug.py

from enum import Enum
from PySide import QtCore, QtGui
import sys
import traceback

class MYENUM(Enum):
  A = 1
  B = 2
  C = 3

def work(val):
  print("'work' called with val {}".format(repr(val)))

class TwoButton(QtGui.QWidget):

  works = QtCore.Signal(str)

  import pdb; pdb.set_trace()
  worksNot = QtCore.Signal(MYENUM)

  def __init__(self):
    super().__init__()
    layout = QtGui.QHBoxLayout()
    btn = QtGui.QPushButton('Works', self)
    layout.addWidget(btn)
    btn.clicked.connect(self.onWorks)
    btn = QtGui.QPushButton('Doesn\'t Work', self)
    layout.addWidget(btn)
    btn.clicked.connect(self.onDoesntWork)
    self.setWindowTitle('Enum Signal Bug Demo')
    self.setLayout(layout)
    self.show()

  def onWorks(self):
    self.works.emit("hello123")
  
  def onDoesntWork(self):
    try:
      self.worksNot.emit(MYENUM.A)
    except:
      traceback.print_exc()

if __name__ == '__main__':
  app = QtGui.QApplication(sys.argv)
  wgt = TwoButton()
  wgt.works.connect(work)
  wgt.worksNot.connect(work)
  sys.exit(app.exec_())

shell

USER@USER-PC:~/scripts$ python3.4 pysideEnumBug.py 
Segmentation fault (core dumped)
USER@USER-PC:~/scripts$ python3.4 pysideEnumBug.py 
> /home/USER/scripts/pysideEnumBug.py(18)TwoButton()
-> worksNot = QtCore.Signal(MYENUM)
(Pdb) s
--Call--
> /usr/lib/python3.4/enum.py(263)__len__()
-> def __len__(cls):
(Pdb) n
> /usr/lib/python3.4/enum.py(264)__len__()
-> return len(cls._member_names_)
(Pdb) s
--Return--
> /usr/lib/python3.4/enum.py(264)__len__()->3
-> return len(cls._member_names_)
(Pdb) s
--Call--
> /usr/lib/python3.4/enum.py(257)__getitem__()
-> def __getitem__(cls, name):
(Pdb) n
> /usr/lib/python3.4/enum.py(258)__getitem__()
-> return cls._member_map_[name]
(Pdb) s
KeyError: 0
> /usr/lib/python3.4/enum.py(258)__getitem__()
-> return cls._member_map_[name]
(Pdb) s
--Return--
> /usr/lib/python3.4/enum.py(258)__getitem__()->None
-> return cls._member_map_[name]
(Pdb) s
Segmentation fault (core dumped)
USER@USER-PC:~/scripts$

"name" in this case is an integer, and PySide uses the length reported by "_len_" to query the various indexes of the MYENUM object. Since Enum doesn't support indexing, it raises a KeyError and this causes the segmentation fault.

If I modify the source code for "enum.Enum._getitem" to accept integers and return the proper item from its internal OrderedDict (e.g. ".getitem_(1)" would return MYENUM.A), the code will compile, but then I'll get "TypeError: worksNot() only accepts 0 arguments, 2 given!" when I try to do "worksNot.emit(MYENUM.A)". I've attached the modified "enum.py" to this bug report.

shell

USER@USER-PC:~/scripts$ python3.4 pysideEnumBug.py 
> /home/USER/scripts/pysideEnumBug.py(19)TwoButton()
-> worksNot = QtCore.Signal(MYENUM)
(Pdb) c
#Click the "Works" button.
'work' called with val 'hello123'
#Click the "Doesn't Work" button.
Traceback (most recent call last):
  File "pysideEnumBug.py", line 39, in onDoesntWork
    self.worksNot.emit(MYENUM.A)
TypeError: worksNot() only accepts 0 arguments, 2 given!

Such an error message is typically a symptom of the target class not deriving from the new Python class type. However, this is Python 3.x; all classes are the new type. For the sake of completeness, I tried modifying the enum.Enum source code to explicitly derive from "object" ("class Enum(object, metaclass=EnumMeta)"), but this did not change the outcome.