Yes, I use the system python. I know I shouldn't. I have updated the __init__.py file, but now get a new error. Perhaps I should do something more than editing the __init__.py file? MG5_aMC>output Test1 INFO: initialize a new directory: Test1 INFO: remove old information in Test1 INFO: Generating Helas calls for process: n5 > ve z QNP<=2 @1 INFO: Processing color information for process: n5 > ve z QNP<=2 @1 INFO: Generating Helas calls for process: n5 > vm z QNP<=2 @1 INFO: Reusing existing color information for process: n5 > vm z QNP<=2 @1 INFO: Generating Helas calls for process: n5 > vt z QNP<=2 @1 INFO: Reusing existing color information for process: n5 > vt z QNP<=2 @1 INFO: Generating Helas calls for process: n5 > a ve QNP<=2 @1 INFO: Processing color information for process: n5 > a ve QNP<=2 @1 INFO: Generating Helas calls for process: n5 > a vm QNP<=2 @1 INFO: Reusing existing color information for process: n5 > a vm QNP<=2 @1 INFO: Generating Helas calls for process: n5 > a vt QNP<=2 @1 INFO: Reusing existing color information for process: n5 > a vt QNP<=2 @1 INFO: Generating Helas calls for process: n5 > a n4 QNP<=2 @1 INFO: Reusing existing color information for process: n5 > a n4 QNP<=2 @1 INFO: Generating Helas calls for process: n5 > a n6 QNP<=2 @1 INFO: Reusing existing color information for process: n5 > a n6 QNP<=2 @1 INFO: Generating Helas calls for process: n5 > ve h QNP<=2 @1 INFO: Reusing existing color information for process: n5 > ve h QNP<=2 @1 INFO: Generating Helas calls for process: n5 > vm h QNP<=2 @1 INFO: Reusing existing color information for process: n5 > vm h QNP<=2 @1 INFO: Generating Helas calls for process: n5 > vt h QNP<=2 @1 INFO: Reusing existing color information for process: n5 > vt h QNP<=2 @1 INFO: Generating Helas calls for process: n5 > e- w+ QNP<=2 @1 INFO: Reusing existing color information for process: n5 > e- w+ QNP<=2 @1 INFO: Generating Helas calls for process: n5 > mu- w+ QNP<=2 @1 INFO: Reusing existing color information for process: n5 > mu- w+ QNP<=2 @1 INFO: Generating Helas calls for process: n5 > ta- w+ QNP<=2 @1 INFO: Reusing existing color information for process: n5 > ta- w+ QNP<=2 @1 INFO: Generating Helas calls for process: n5 > e+ w- QNP<=2 @1 INFO: Reusing existing color information for process: n5 > e+ w- QNP<=2 @1 INFO: Generating Helas calls for process: n5 > mu+ w- QNP<=2 @1 INFO: Reusing existing color information for process: n5 > mu+ w- QNP<=2 @1 INFO: Generating Helas calls for process: n5 > ta+ w- QNP<=2 @1 INFO: Reusing existing color information for process: n5 > ta+ w- QNP<=2 @1 INFO: Generating Helas calls for process: n5 > z n4 QNP<=2 @1 INFO: Reusing existing color information for process: n5 > z n4 QNP<=2 @1 INFO: Generating Helas calls for process: n5 > z n6 QNP<=2 @1 INFO: Reusing existing color information for process: n5 > z n6 QNP<=2 @1 INFO: Generating Helas calls for process: n5 > h n4 QNP<=2 @1 INFO: Reusing existing color information for process: n5 > h n4 QNP<=2 @1 INFO: Generating Helas calls for process: n5 > h n5 QNP<=2 @1 INFO: Reusing existing color information for process: n5 > h n5 QNP<=2 @1 INFO: Generating Helas calls for process: n5 > h n6 QNP<=2 @1 INFO: Reusing existing color information for process: n5 > h n6 QNP<=2 @1 INFO: Creating files in directory P1_n5_vez INFO: Generating Feynman diagrams for Process: n5 > ve z QNP<=2 @1 INFO: Creating files in directory P1_n5_vmz INFO: Generating Feynman diagrams for Process: n5 > vm z QNP<=2 @1 INFO: Creating files in directory P1_n5_vtz INFO: Generating Feynman diagrams for Process: n5 > vt z QNP<=2 @1 INFO: Creating files in directory P1_n5_ave INFO: Generating Feynman diagrams for Process: n5 > a ve QNP<=2 @1 INFO: Creating files in directory P1_n5_avm INFO: Generating Feynman diagrams for Process: n5 > a vm QNP<=2 @1 INFO: Creating files in directory P1_n5_avt INFO: Generating Feynman diagrams for Process: n5 > a vt QNP<=2 @1 INFO: Creating files in directory P1_n5_an4 INFO: Generating Feynman diagrams for Process: n5 > a n4 QNP<=2 @1 INFO: Creating files in directory P1_n5_an6 INFO: Generating Feynman diagrams for Process: n5 > a n6 QNP<=2 @1 INFO: Creating files in directory P1_n5_veh INFO: Generating Feynman diagrams for Process: n5 > ve h QNP<=2 @1 INFO: Creating files in directory P1_n5_vmh INFO: Generating Feynman diagrams for Process: n5 > vm h QNP<=2 @1 INFO: Creating files in directory P1_n5_vth INFO: Generating Feynman diagrams for Process: n5 > vt h QNP<=2 @1 INFO: Creating files in directory P1_n5_emwp INFO: Generating Feynman diagrams for Process: n5 > e- w+ QNP<=2 @1 INFO: Creating files in directory P1_n5_mumwp INFO: Generating Feynman diagrams for Process: n5 > mu- w+ QNP<=2 @1 INFO: Creating files in directory P1_n5_tamwp INFO: Generating Feynman diagrams for Process: n5 > ta- w+ QNP<=2 @1 INFO: Creating files in directory P1_n5_epwm INFO: Generating Feynman diagrams for Process: n5 > e+ w- QNP<=2 @1 INFO: Creating files in directory P1_n5_mupwm INFO: Generating Feynman diagrams for Process: n5 > mu+ w- QNP<=2 @1 INFO: Creating files in directory P1_n5_tapwm INFO: Generating Feynman diagrams for Process: n5 > ta+ w- QNP<=2 @1 INFO: Creating files in directory P1_n5_zn4 INFO: Generating Feynman diagrams for Process: n5 > z n4 QNP<=2 @1 INFO: Creating files in directory P1_n5_zn6 INFO: Generating Feynman diagrams for Process: n5 > z n6 QNP<=2 @1 INFO: Creating files in directory P1_n5_hn4 INFO: Generating Feynman diagrams for Process: n5 > h n4 QNP<=2 @1 INFO: Creating files in directory P1_n5_hn5 INFO: Generating Feynman diagrams for Process: n5 > h n5 QNP<=2 @1 INFO: Creating files in directory P1_n5_hn6 INFO: Generating Feynman diagrams for Process: n5 > h n6 QNP<=2 @1 Generated helas calls for 22 subprocesses (25 diagrams) in 0.020 s Wrote files for 91 helas calls in 0.388 s Command "output Test1" interrupted with error: UFOError : No module named 'heavyNeff4_UFO' Please report this bug on https://bugs.launchpad.net/mg5amcnlo More information is found in 'MG5_debug'. 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