Python3 compatibility issues

[jamesobutler]

There are some compatibilities issues that were found by a user using the recent Slicer nightly which uses Python3.

https://discourse.slicer.org/t/simple-filters-module-do-not-have-any-filters-in-latest-nightly-version/6787

• On loading module

  Error while reading "C:\Program Files\Slicer 4.11.0-2019-05-13\lib\Slicer-4.11\qt-scripted-modules/Resources/json\AbsImageFilter.json". Exception: name 'file' is not defined
  Error while reading "C:\Program Files\Slicer 4.11.0-2019-05-13\lib\Slicer-4.11\qt-scripted-modules/Resources/json\AbsoluteValueDifferenceImageFilter.json". Exception: name 'file' is not defined
  Error while reading "C:\Program Files\Slicer 4.11.0-2019-05-13\lib\Slicer-4.11\qt-scripted-modules/Resources/json\AcosImageFilter.json". Exception: name 'file' is not defined
  .
  .
  .

• Upon selecting one of the filters after changing file() usage to open(), there were more errors:

  Traceback (most recent call last):
  File "C:/Program Files/Slicer 4.11.0-2019-05-13/bin/../lib/Slicer-4.11/qt-scripted-modules/SimpleFilters.py", line 268, in onFilterSelect
  self.filterParameters.create(json)
  File "C:/Program Files/Slicer 4.11.0-2019-05-13/bin/../lib/Slicer-4.11/qt-scripted-modules/SimpleFilters.py", line 817, in create
  w = self.createIntWidget(member["name"],t)
  File "C:/Program Files/Slicer 4.11.0-2019-05-13/bin/../lib/Slicer-4.11/qt-scripted-modules/SimpleFilters.py", line 963, in createIntWidget
  w.setValue(int(default))
  NameError: name 'default' is not defined

More issues might be present, but these were the first I have noticed.

[blowekamp]

Thank you for reporting the issue. Is this bug in the currently posted nightly build?

[jamesobutler]

Yes. Slicer nightly was download from slicer.org today as indicated by C:\Program Files\Slicer 4.11.0-2019-05-13 in the errors above.

[blowekamp]

It looks like Python3 may not be as forgiving with joining paths on windows with a mix of '\' and '/' slashes. I believe the issue is here on these lines: https://github.com/SimpleITK/SlicerSimpleFilters/blob/12efaabb0151c270e61bc7a3b3d08ad4c8db8095/SimpleFilters/SimpleFilters.py#L35-L36

and like would only present itself on windows. I would think changing:

ICON_DIR = os.path.dirname(os.path.realpath(__file__)) + '/Resources/Icons/'

to

ICON_DIR = os.path.join( os.path.dirname(os.path.realpath(__file__)), 'Resources', 'Icons')
JSON_DIR = os.path.join( os.path.dirname(os.path.realpath(__file__)), 'Resources, 'json')

Are you able to give that change a try?

[jamesobutler]

Changing https://github.com/SimpleITK/SlicerSimpleFilters/blob/12efaabb0151c270e61bc7a3b3d08ad4c8db8095/SimpleFilters/SimpleFilters.py#L105 to use open() fixes the initial error.

The second error is something related to these type of calls where "default" is now undefined in python3. Changing the joining of paths doesn't solve this issue. https://github.com/SimpleITK/SlicerSimpleFilters/blob/12efaabb0151c270e61bc7a3b3d08ad4c8db8095/SimpleFilters/SimpleFilters.py#L962-L963

[blowekamp]

nice job tracking done the file error!

[jamesobutler]

Closed by #19.