pyqtgraph/examples/initExample.py

## make this version of pyqtgraph importable before any others
## we do this to make sure that, when running examples, the correct library
## version is imported (if there are multiple versions present).
import sys, os

if not hasattr(sys, 'frozen'):
    if __file__ == '<stdin>':
        path = os.getcwd()
    else:
        path = os.path.abspath(os.path.join(os.path.dirname(__file__), '..'))
    path.rstrip(os.path.sep)
    if 'pyqtgraph' in os.listdir(path):
        sys.path.insert(0, path) ## examples adjacent to pyqtgraph (as in source tree)
    else:
        for p in sys.path:
            if len(p) < 3:
                continue
            if path.startswith(p):  ## If the example is already in an importable location, promote that location
                sys.path.remove(p)
                sys.path.insert(0, p)

## should force example to use PySide instead of PyQt
if 'pyside' in sys.argv:  
    from PySide import QtGui
elif 'pyqt' in sys.argv: 
    from PyQt4 import QtGui
else:
    from pyqtgraph.Qt import QtGui
    
## Force use of a specific graphics system
for gs in ['raster', 'native', 'opengl']:
    if gs in sys.argv:
        QtGui.QApplication.setGraphicsSystem(gs)
        break