def dist(a, b):
    return sum((i-j)**2 for i, j in zip(a, b))
def activate(self, callingWindow, fullContext, mainItem, i):
        fitID = self.mainFrame.getActiveFit()
        Fit.getInstance().setAsPattern(fitID, mainItem)
        wx.PostEvent(self.mainFrame, GE.FitChanged(fitIDs=(fitID,)))