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"""
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This module contains factory functions that attempt
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to return Qt submodules from the various python Qt bindings.
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It also protects against double-importing Qt with different
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bindings, which is unstable and likely to crash
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This is used primarily by qt and qt_for_kernel, and shouldn't
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be accessed directly from the outside
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"""
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import sys
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from functools import partial
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from IPython.utils.version import check_version
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# Available APIs.
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QT_API_PYQT = 'pyqt'
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QT_API_PYQTv1 = 'pyqtv1'
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QT_API_PYQT_DEFAULT = 'pyqtdefault' # don't set SIP explicitly
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QT_API_PYSIDE = 'pyside'
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class ImportDenier(object):
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"""Import Hook that will guard against bad Qt imports
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once IPython commits to a specific binding
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"""
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def __init__(self):
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self.__forbidden = None
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def forbid(self, module_name):
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sys.modules.pop(module_name, None)
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self.__forbidden = module_name
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def find_module(self, fullname, path=None):
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if path:
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return
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if fullname == self.__forbidden:
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return self
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def load_module(self, fullname):
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raise ImportError("""
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Importing %s disabled by IPython, which has
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already imported an Incompatible QT Binding: %s
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""" % (fullname, loaded_api()))
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ID = ImportDenier()
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sys.meta_path.append(ID)
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def commit_api(api):
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"""Commit to a particular API, and trigger ImportErrors on subsequent
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dangerous imports"""
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if api == QT_API_PYSIDE:
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ID.forbid('PyQt4')
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else:
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ID.forbid('PySide')
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def loaded_api():
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"""Return which API is loaded, if any
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If this returns anything besides None,
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importing any other Qt binding is unsafe.
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Returns
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-------
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None, 'pyside', 'pyqt', or 'pyqtv1'
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"""
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if 'PyQt4.QtCore' in sys.modules:
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if qtapi_version() == 2:
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return QT_API_PYQT
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else:
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return QT_API_PYQTv1
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elif 'PySide.QtCore' in sys.modules:
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return QT_API_PYSIDE
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return None
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def has_binding(api):
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"""Safely check for PyQt4 or PySide, without importing
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submodules
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Parameters
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----------
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api : str [ 'pyqtv1' | 'pyqt' | 'pyside' | 'pyqtdefault']
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Which module to check for
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Returns
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-------
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True if the relevant module appears to be importable
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"""
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# we can't import an incomplete pyside and pyqt4
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# this will cause a crash in sip (#1431)
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# check for complete presence before importing
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module_name = {QT_API_PYSIDE: 'PySide',
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QT_API_PYQT: 'PyQt4',
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QT_API_PYQTv1: 'PyQt4',
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QT_API_PYQT_DEFAULT: 'PyQt4'}
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module_name = module_name[api]
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import imp
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try:
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#importing top level PyQt4/PySide module is ok...
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mod = __import__(module_name)
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#...importing submodules is not
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imp.find_module('QtCore', mod.__path__)
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imp.find_module('QtGui', mod.__path__)
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imp.find_module('QtSvg', mod.__path__)
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#we can also safely check PySide version
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if api == QT_API_PYSIDE:
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return check_version(mod.__version__, '1.0.3')
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else:
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return True
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except ImportError:
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return False
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def qtapi_version():
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"""Return which QString API has been set, if any
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Returns
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-------
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The QString API version (1 or 2), or None if not set
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"""
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try:
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import sip
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except ImportError:
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return
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try:
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return sip.getapi('QString')
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except ValueError:
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return
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def can_import(api):
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"""Safely query whether an API is importable, without importing it"""
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if not has_binding(api):
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return False
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current = loaded_api()
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if api == QT_API_PYQT_DEFAULT:
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return current in [QT_API_PYQT, QT_API_PYQTv1, None]
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else:
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return current in [api, None]
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def import_pyqt4(version=2):
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"""
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Import PyQt4
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Parameters
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----------
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version : 1, 2, or None
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Which QString/QVariant API to use. Set to None to use the system
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default
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ImportErrors rasied within this function are non-recoverable
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"""
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# The new-style string API (version=2) automatically
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# converts QStrings to Unicode Python strings. Also, automatically unpacks
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# QVariants to their underlying objects.
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import sip
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if version is not None:
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sip.setapi('QString', version)
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sip.setapi('QVariant', version)
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from PyQt4 import QtGui, QtCore, QtSvg
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if not check_version(QtCore.PYQT_VERSION_STR, '4.7'):
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raise ImportError("IPython requires PyQt4 >= 4.7, found %s" %
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QtCore.PYQT_VERSION_STR)
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# Alias PyQt-specific functions for PySide compatibility.
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QtCore.Signal = QtCore.pyqtSignal
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QtCore.Slot = QtCore.pyqtSlot
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# query for the API version (in case version == None)
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version = sip.getapi('QString')
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api = QT_API_PYQTv1 if version == 1 else QT_API_PYQT
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return QtCore, QtGui, QtSvg, api
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def import_pyside():
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"""
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Import PySide
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ImportErrors raised within this function are non-recoverable
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"""
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from PySide import QtGui, QtCore, QtSvg
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return QtCore, QtGui, QtSvg, QT_API_PYSIDE
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def load_qt(api_options):
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"""
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Attempt to import Qt, given a preference list
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of permissible bindings
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It is safe to call this function multiple times.
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Parameters
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----------
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api_options: List of strings
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The order of APIs to try. Valid items are 'pyside',
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'pyqt', and 'pyqtv1'
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Returns
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-------
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A tuple of QtCore, QtGui, QtSvg, QT_API
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The first three are the Qt modules. The last is the
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string indicating which module was loaded.
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Raises
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------
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ImportError, if it isn't possible to import any requested
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bindings (either becaues they aren't installed, or because
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an incompatible library has already been installed)
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"""
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loaders = {QT_API_PYSIDE: import_pyside,
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QT_API_PYQT: import_pyqt4,
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QT_API_PYQTv1: partial(import_pyqt4, version=1),
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QT_API_PYQT_DEFAULT: partial(import_pyqt4, version=None)
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}
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for api in api_options:
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if api not in loaders:
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raise RuntimeError(
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"Invalid Qt API %r, valid values are: %r, %r, %r, %r" %
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(api, QT_API_PYSIDE, QT_API_PYQT,
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QT_API_PYQTv1, QT_API_PYQT_DEFAULT))
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if not can_import(api):
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continue
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#cannot safely recover from an ImportError during this
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result = loaders[api]()
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api = result[-1] # changed if api = QT_API_PYQT_DEFAULT
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commit_api(api)
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return result
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else:
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raise ImportError("""
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Could not load requested Qt binding. Please ensure that
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PyQt4 >= 4.7 or PySide >= 1.0.3 is available,
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and only one is imported per session.
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Currently-imported Qt library: %r
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PyQt4 installed: %s
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PySide >= 1.0.3 installed: %s
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Tried to load: %r
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""" % (loaded_api(),
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has_binding(QT_API_PYQT),
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has_binding(QT_API_PYSIDE),
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api_options))
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