from processing.core.Processing import Processing
from processing.gui.AlgorithmDialog import AlgorithmDialog

def runAlgorithm(alg):
    """ Borrowed from CommanderWindow.py, from Processing framework """
    alg = alg.getCopy()
    message = alg.checkBeforeOpeningParametersDialog()
    if message:
        print message
        return
    dlg = alg.getCustomParametersDialog()
    if not dlg:
        dlg = AlgorithmDialog(alg)
    canvas = iface.mapCanvas()
    prevMapTool = canvas.mapTool()
    dlg.show()
    dlg.exec_()
    if canvas.mapTool() != prevMapTool:
        try:
            canvas.mapTool().reset()
        except:
            pass
        canvas.setMapTool(prevMapTool)

alg = Processing.getAlgorithm("qgis:joinattributestable") # Adjust this to your needs
if alg is not None:
   runAlgorithm(alg)

import processing
processing.alglist()