AM_MPC py2.7

sel = mc.ls(selection=True)
mc.select(d=True)

mpc_childrens = sel[:-1]
mpc_parent = sel[-1]

if sel:
    for t in sel:
        if mc.nodeType(t) != 'transform' and len(sel) < 3:
            mc.warning('Select 3 transforms mini')

        else:
            for p in mpc_childrens:
                mc.parentConstraint(mpc_parent, p, mo=True)

            mc.select(mpc_parent, r=True)
else:
    mc.warning('Select 3 transforms mini')