* Saved README.txt of the lmod_python fix (notes written to Minhao, 2020-06-09).

lmod/ipython/startup/README.txt

@@ -0,0 +1,43 @@
+Date: 2020-06-09
+
+Purpose: troubleshoot & fix the ipython startup file
+which caused issue.
+
+The original setup (combined `000-odurc-lmod.py` and `lmod_python.py`)
+have several issues:
+
+* On Turing (vanilla ipython), could not find the module command.
+
+* On Wahab (vanilla ipython), invoking the "module" command resulted
+  in an error due to unset `LMOD_MANUAL_LD_LIBRARY_PATH` env var.
+
+* On Wahab/OOD, the "module" command messed up all the symlinks in the
+  specially prepared library dir (LMOD_MANUAL_LD_LIBRARY_PATH).
+  As a result, all symlinks become circular links.
+
+I fixed these files with the following improvements:
+
+1) Allow the setup to work on both Wahab and Turing. (The new
+   `lmod_python.py` needs to be installed somewhere on Turing;
+   I made up the location to be
+   `/cm/shared/applications/lmod/lmod/scripts/init`.
+
+2) Fix the indefinite lengthening of `sys.path` as a result of
+   "module" command invocation: now only the *changes* are updated
+   onto `sys.path`. Still not perfect (see notes in the Python code)
+   but should work ok for most cases.
+
+3) As a result of fix #2 above, when we invoke `module("unload",
+   A_MODULE)`, the paths associated with `A_MODULE` will also be removed.
+
+4) Fix the "circular links" problem. If `LMOD_MANUAL_LD_LIBRARY_PATH`
+   is not specified, it quietly ignores the symlink update process.
+
+See if you like these changes---I suggest implementing them soon.
+
+I found that the existing `000-odurc-lmod.py` is always overwritten
+whenever I launch Jupyter on Wahab OOD. It was due to `before.sh` of
+the OOD Jupyter notebook setup ... grrr. I know you assume that users
+won't mess with this file (but I did, while doing all this testing).
+I'll make my own workaround.
+