Use the same logic as MPL uses when picking Qt interface.

Daniel O'Connor · Daniel O'Connor · commit f8855f248bb2 · 2013-07-17T22:02:13.000+09:30
Thanks to Michael Droettboom (matplotlib#2221 (comment))
diff --git a/examples/animation/old_animation/animation_blit_qt4.py b/examples/animation/old_animation/animation_blit_qt4.py
@@ -11,9 +11,12 @@
 from matplotlib.figure import Figure
 from matplotlib.backends.backend_qt4agg import FigureCanvasQTAgg as FigureCanvas
 
-try:
+from matplotlib.backends import qt4_compat
+use_pyside = qt4_compat.QT_API == qt4_compat.QT_API_PYSIDE
+
+if use_pyside:
     from PySide import QtCore, QtGui
-except ImportError:
+else:
     from PyQt4 import QtCore, QtGui
 
 ITERS = 1000
diff --git a/examples/user_interfaces/embedding_in_qt4.py b/examples/user_interfaces/embedding_in_qt4.py
@@ -11,12 +11,12 @@
 
 from __future__ import unicode_literals
 import sys, os, random
-try:
+from matplotlib.backends import qt4_compat
+use_pyside = qt4_compat.QT_API == qt4_compat.QT_API_PYSIDE
+if use_pyside:
     from PySide import QtGui, QtCore
-    usepyside = True
-except ImportError:
+else:
     from PyQt4 import QtGui, QtCore
-    usepyside = False
 
 from numpy import arange, sin, pi
 from matplotlib.backends.backend_qt4agg import FigureCanvasQTAgg as FigureCanvas
@@ -62,7 +62,7 @@ class MyDynamicMplCanvas(MyMplCanvas):
     def __init__(self, *args, **kwargs):
         MyMplCanvas.__init__(self, *args, **kwargs)
         timer = QtCore.QTimer(self)
-        if usepyside: 
+        if use_pyside: 
             timer.timeout.connect(self.update_figure)
         else:
             QtCore.QObject.connect(timer, QtCore.SIGNAL("timeout()"), self.update_figure)
diff --git a/examples/user_interfaces/embedding_in_qt4_wtoolbar.py b/examples/user_interfaces/embedding_in_qt4_wtoolbar.py
@@ -8,10 +8,13 @@
 from matplotlib.backends.backend_qt4agg import (
     FigureCanvasQTAgg as FigureCanvas,
     NavigationToolbar2QTAgg as NavigationToolbar)
-try:
+from matplotlib.backends import qt4_compat
+use_pyside = qt4_compat.QT_API == qt4_compat.QT_API_PYSIDE
+
+if use_pyside:
     from PySide.QtCore import *
     from PySide.QtGui import *
-except ImportError:
+else:
     from PyQt4.QtCore import *
     from PyQt4.QtGui import *
 
