Compiling Gildas with Python 2, bypassing Python 3

Python 3 is now the default python executable under some Linux distributions, but it is not yet supported by the Gildas-Python binding. You can still compile and use Gildas with Python 2, with a few restrictions.

1. first make sure Python 2 (executable, headers and libraries) are available on your system. It is very likely they are available on your system e.g. the executable is /usr/bin/python2. If not, you can compile your own Python version (see Section 3.1.2).
2. make temporarily Python 2 the default, i.e. the python command should start Python 2. You can achieve this by putting e.g. a symlink named python pointing to python2 in your $PATH (for example in your $HOME/bin).
3. compile Gildas, and check carefully the messages related to Python during the command source admin/gildas-env.sh. They should all refer to your Python 2 installation.

If you followed correctly the above points, Gildas is now binded to the Python 2 libraries. You have then 2 possibilities:

• if you use Python inside Gildas (i.e. SIC$\backslash$PYTHON commands), you can safely revert the python command to its original state. Gildas will use independently of it the Python 2 libraries, including its specific syntax and rules.
• if you use the Gildas-Python modules (e.g. pygreg, pyclass) in Python, then you must import them in the Python 2 executable. Either you keep permanently the symlink python to python2 the default, either you call explicitly python2 before importing the modules. Here also this means you have to use Python 2 syntax and rules.