Hi, This is related to bug http://www.lyx.org/trac/ticket/8950
The problem is the following. Currently, to find python2, LyX: - checks the python command is a valid python 2 executable - if so, it just stores that the python command is “python” (otherwise, it searches and uses an absolute path - leading to no bug) - when reading lyxrc, or changing preferences, the PATH might be changed. If (and it happens) the first “python” in the PATH is python 3, then LyX breaks completely (on OS X, no menu is displayed, nothing happens). Besides fixing the LyX behavior when python scripts fail, there are two solutions: - ensure that python is an absolute path by directly checking the different installed python within PATH: this might break in some very corner case and the patch is really trivial (on the bug page). The only corner case is the following: python is uninstalled while LyX is running, or the matching python is replaced by another one (this can happen); - use a new lyxrc entry (pythonpath) that could be set in the preferences. This can break in the same case. - recheck the PATH every time it is changed. This breaks in the same case. The second solution has the advantage of storing the value for future LyX runs. It would need to be further enhanced by: - check each time (or on fail) that the current python is a python2 installation; - warn if python2 cannot be found and ask the user to provide a path to a valid one. Latter, those checks could be just to have a valid python2/3 installation. This is important given the important role played by python in LyX. Benjamin
