pyqtgraph < 0.10 fail to run from pyqtgraph import __version__ , us…

[k-okada]

…e pkg_resources

@dirk-thomas 's fix at ros-visualization/rqt_common_plugins#415 failing on default kinetic enviroment whcih uses 0.9.10 of python-pyqtgraph https://packages.ubuntu.com/xenial/python-pyqtgraph

$ rqt_plot /joint_state/position[0]
Traceback (most recent call last):
  File "/opt/ros/kinetic/bin/rqt_plot", line 6, in <module>
    from rqt_plot.plot import Plot
  File "/opt/ros/kinetic/lib/python2.7/dist-packages/rqt_plot/plot.py", line 43, in <module>
    from .data_plot import DataPlot
  File "/opt/ros/kinetic/lib/python2.7/dist-packages/rqt_plot/data_plot/__init__.py", line 44, in <module>
    from .pyqtgraph_data_plot import PyQtGraphDataPlot
  File "/opt/ros/kinetic/lib/python2.7/dist-packages/rqt_plot/data_plot/pyqtgraph_data_plot.py", line 46, in <module>
    from pyqtgraph import __version__ as pyqtgraph_version
  File "/usr/lib/python2.7/dist-packages/pyqtgraph/__init__.py", line 13, in <module>
    from .Qt import QtGui
  File "/usr/lib/python2.7/dist-packages/pyqtgraph/Qt.py", line 104, in <module>
    from PyQt4 import QtGui, QtCore, uic
RuntimeError: the PyQt4.QtCore and PyQt5.QtCore modules both wrap the QObject class

[dirk-thomas]

The python-pyqtgraph package on Xenial is using Qt 4 and will therefore not be compatible with RQt in Kinetic because it targets Qt 5 (hence the version check).

I am not sure what this patch should achieve - especially since the version comparion is left untouched which raises a RuntimeError for that version of pyqtgraph?

[k-okada]

from pyqtgraph import __version__ as pyqtgraph_version itself failed with pyqtgraph < 0.10 (?) because , when we evaluate this line, it also try to read all

  File "/usr/lib/python2.7/dist-packages/pyqtgraph/__init__.py", line 13, in <module>

file and that includes

    from .Qt import QtGui

which raises error

RuntimeError: the PyQt4.QtCore and PyQt5.QtCore modules both wrap the QObject class

as seen in error message.

This PR catch this exception and try with other method, using pkg_resource to get the version number string. May be

- from pyqtgraph import __version__ as pyqtgraph_version
+ import pkg_resources
+ pyqtgraph_version = pkg_resources.get_distribution("pyqtgraph").version

would be ok.

[dirk-thomas]

Please catch a specific exception type here as well as add a comment when it is expected to be raised.

[k-okada]

@dirk-thomas sorry for late, updated to catch only "RuntimeError"

[dirk-thomas]

Thank you for the patch and the update.