try:
    from PySide import QtCore, QtGui
except ImportError:
    from PyQt4 import QtCore, QtGui

def gui_fname(dir=None):
    """Select a file via a dialog and returns the file name.
    """
    if dir is None: dir ='./'
    fname = QtGui.QFileDialog.getOpenFileName(None, "Select data file...", 
            dir, filter="All files (*);; SM Files (*.sm)")
    return fname[0]

full_fname = gui_fname()

%gui qt
full_fname = gui_fname()
%matplotlib inline

%gui qt

%gui qt
file_name = gui_fname()
%matplotlib inline

file_name