Install                                          8/7/2020  Wesley Ebisuzaki

Preliminaries:

   1. Python 3.5+ has to be installed  (I have not tried on older versions of python3)
   2. numpy has to be installed
   3. find a directory on your python path to store pywgrib2_s.py and libwgrib2.so
       call this directory PYTHON_DIR

Step 1: make wgrib2 shared library and wgrib2 executable

  Download wgrib2.tgz from https://ftp.cpc.ncep.noaa.gov/wd51we/tmp/wgrib2.tgz
       This is a release candidate wgrib2 v3.0.0.

       $ tar -xzvf wgrib2.tgz
       $ cd grib2
       edit ./makefile to make a shared library
       $ make
       $ make lib
       $ cp lib/libwgrib2.so PYTHON_DIR/

Step 2: Configure pywgrib2_s.py to  PYTHON_DIR.

Testing:

    Try running python 3.x and importing pywgrib2_s

A Good Result:

ebis@landing2:~$ python3.8 
Python 3.8.2 (default, Jul 16 2020, 14:00:26) 
[GCC 9.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import pywgrib2_s
finished loading libraries
pywgrib2_s v0.0.7 7-30-2020 w. ebisuzaki
>>> 

A Bad Result:

-sh-4.1$ python3.5
Python 3.5.2 |Anaconda 4.2.0 (64-bit)| (default, Jul  2 2016, 17:53:06) 
[GCC 4.4.7 20120313 (Red Hat 4.4.7-1)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import pywgrib2_s
*** Problem  libquadmath.so.0: cannot open shared object file: No such file or directory
*** Will load wgrib2 library in RTLD_LAZY mode
Traceback (most recent call last):
  File "/export/cpc-lw-webisuzak/wd51we/.local/lib/python3.5/site-packages/pywgrib2_s.py", line 29, in <module>
    my_wgrib2=CDLL(lib)
  File "/cpc/prod/cpcwebapps/software/anaconda/lib/python3.5/ctypes/__init__.py", line 347, in __init__
    self._handle = _dlopen(self._name, mode)
OSError: libquadmath.so.0: cannot open shared object file: No such file or directory

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/export/cpc-lw-webisuzak/wd51we/.local/lib/python3.5/site-packages/pywgrib2_s.py", line 33, in <module>
    my_wgrib2=CDLL(lib, mode=os.RTLD_LAZY)
  File "/cpc/prod/cpcwebapps/software/anaconda/lib/python3.5/ctypes/__init__.py", line 347, in __init__
    self._handle = _dlopen(self._name, mode)
OSError: libquadmath.so.0: cannot open shared object file: No such file or directory
>>> 

This is a problem with Anaconda because uses its own shared libraries in 
preference over the system shared libraries.  The system shared libraries 
do not use libquadmath.so, so that library is not installed.  However,
the Anaconda's shared libraries are different from the system libraries and 
they refer to libquadmath.so, and do not include a copy of libquadmath.so.  
This is a mistake by Anaconda for not incuding libquadmath.so.  It is 
also a poor decision by Anaconda for using their copy of the shared library 
over the system library of the same name.  It is also a mistake by Anaconda 
for changing the search path for libraries from the python documentation.


To work around Anaconda's feature, you have to edit pywgrib2_s.py and add
a CDLL the gfortran library using a full path name.  The names and locations
will depend on your system.