From fd32adbcfa084c0217d5ff7ecd0fea44dce8bdd1 2017-01-12 15:16:13
From: Thomas Kluyver <thomas@kluyver.me.uk>
Date: 2017-01-12 15:16:13
Subject: [PATCH] New implementation of has_binding Qt check for Python 3.4+

Closes gh-10080

---

diff --git a/IPython/external/qt_loaders.py b/IPython/external/qt_loaders.py
index 860a570..e16cb2a 100644
--- a/IPython/external/qt_loaders.py
+++ b/IPython/external/qt_loaders.py
@@ -21,6 +21,15 @@ QT_API_PYQT5 = 'pyqt5'
 QT_API_PYQTv1 = 'pyqtv1' # Force version 2
 QT_API_PYQT_DEFAULT = 'pyqtdefault' # use system default for version 1 vs. 2
 QT_API_PYSIDE = 'pyside'
+QT_API_PYSIDE2 = 'pyside2'
+
+api_to_module = {QT_API_PYSIDE2: 'PySide2',
+                 QT_API_PYSIDE: 'PySide',
+                 QT_API_PYQT: 'PyQt4',
+                 QT_API_PYQTv1: 'PyQt4',
+                 QT_API_PYQT5: 'PyQt5',
+                 QT_API_PYQT_DEFAULT: 'PyQt4',
+                }
 
 
 class ImportDenier(object):
@@ -89,8 +98,9 @@ def loaded_api():
 
 
 def has_binding(api):
-    """Safely check for PyQt4/5 or PySide, without importing
-       submodules
+    """Safely check for PyQt4/5 or PySide, without importing submodules
+
+    Supports Python <= 3.3
 
        Parameters
        ----------
@@ -104,12 +114,7 @@ def has_binding(api):
     # we can't import an incomplete pyside and pyqt4
     # this will cause a crash in sip (#1431)
     # check for complete presence before importing
-    module_name = {QT_API_PYSIDE: 'PySide',
-                   QT_API_PYQT: 'PyQt4',
-                   QT_API_PYQTv1: 'PyQt4',
-                   QT_API_PYQT5: 'PyQt5',
-                   QT_API_PYQT_DEFAULT: 'PyQt4'}
-    module_name = module_name[api]
+    module_name = api_to_module[api]
 
     import imp
     try:
@@ -131,6 +136,48 @@ def has_binding(api):
     except ImportError:
         return False
 
+def has_binding_new(api):
+    """Safely check for PyQt4/5 or PySide, without importing submodules
+
+    Supports Python >= 3.4
+
+        Parameters
+        ----------
+        api : str [ 'pyqtv1' | 'pyqt' | 'pyqt5' | 'pyside' | 'pyqtdefault']
+             Which module to check for
+
+        Returns
+        -------
+        True if the relevant module appears to be importable
+     """
+    module_name = api_to_module[api]
+    from importlib.util import find_spec
+
+    required = ['QtCore', 'QtGui', 'QtSvg']
+    if api in (QT_API_PYQT5, QT_API_PYSIDE2):
+        # QT5 requires QtWidgets too
+        required.append('QtWidgets')
+
+    for submod in required:
+        try:
+            spec = find_spec('%s.%s' % (module_name, submod))
+        except ImportError:
+            # Package (e.g. PyQt5) not found
+            return False
+        else:
+            if spec is None:
+                # Submodule (e.g. PyQt5.QtCore) not found
+                return False
+
+    if api == QT_API_PYSIDE:
+        # We can also safely check PySide version
+        import PySide
+        return check_version(PySide.__version__, '1.0.3')
+
+    return True
+
+if sys.version_info >= (3, 4):
+    has_binding = has_binding_new
 
 def qtapi_version():
     """Return which QString API has been set, if any