Update python embedding docs to list required packages for the base p…

…ython version.

met/docs/Users_Guide/appendixF.rst

@@ -6,13 +6,15 @@ Appendix F Python Embedding
 Introduction
 ____________
 
-MET includes the ability to embed Python to a limited degree. Users may use Python scripts and whatever associated Python packages they wish in order to prepare 2D gridded data fields, point observations, and matched pairs as input to the MET tools. We fully expect that this degree of embedding will increase in the future. In addition, plans are in place to extend Python with MET in upcoming releases, allowing users to invoke MET tools directly from their Python script. While MET version 8.0 was built on Python 2.x, MET version 9.0 is built on Python 3.6+. 
+MET includes the ability to embed Python to a limited degree. Users may use Python scripts and whatever associated Python packages they wish in order to prepare 2D gridded data fields, point observations, and matched pairs as input to the MET tools. We fully expect that this degree of embedding will increase in the future. In addition, plans are in place to extend Python with MET in upcoming releases, allowing users to invoke MET tools directly from their Python script. While MET version 8.0 was built on Python 2.x, MET versions 9.0 and beyond are built on Python 3.6+.
 
 Compiling Python Support
 ________________________
 
 In order to use Python embedding, the user's local Python installation must have the C-language Python header files and libraries. Sometimes when Python is installed locally, these header files and libraries are deleted at the end of the installation process, leaving only the binary executable and run-time shared object files. But the Python header files and libraries must be present to compile support in MET for Python embedding. Assuming the requisite Python files are present, and that Python embedding is enabled when building MET (which is done by passing the **--enable-python** option to the **configure** command line), the MET C++ code will use these in the compilation process to link directly to the Python libraries.
 
+The local Python installation must also support a minimum set of required packages. The MET build includes some python wrapper scripts to facilitate the passing of data in memory as well as the reading and writing of temporary files. The packages required by those wrapper scripts are **sys, os, argparse, importlib, numpy and netCDF4**. While most of these are standard packages and readily available, numpy and netCDF4 may not be. Users are advised to confirm their availability prior to compiling MET with python embedding support.
+
 In addition to the **configure** option mentioned above, two variables, **MET_PYTHON_CC** and **MET_PYTHON_LD**, must also be set for the configuration process. These may either be set as environment variables or as command line options to **configure**. These constants are passed as compiler command line options when building MET to enable the compiler to find the requisite Python header files and libraries in the user's local filesystem. Fortunately, Python provides a way to set these variables properly. This frees the user from the necessity of having any expert knowledge of the compiling and linking process. Along with the **Python** executable, there should be another executable called **python3-config**, whose output can be used to set these environment variables as follows:
 
 • On the command line, run “**python3-config --cflags**”. Set the value of **MET_PYTHON_CC** to the output of that command.

met/docs/Users_Guide/installation.rst

@@ -177,7 +177,7 @@ The following environment variables should also be set:
     MET_PYTHON_CC='-I/usr/include/python3.6'
     MET_PYTHON_LD='-L/usr/lib/python3.6/config-x86_64-linux-gnu -lpython3.6m'
 
-  For more information about Python support in MET, please refer to :numref:`Appendix F, Section %s <appendixF>`.
+  Note that this version of Python must include support for a minimum set of required pacakges. For more information about Python support in MET, including the list of required packages, please refer to :numref:`Appendix F, Section %s <appendixF>`.
 
 
 * If compiling MODIS-Regrid and/or lidar2nc, set $MET_HDF to point to the main HDF4 directory, or set $MET_HDFINC to point to the directory with the HDF4 include files and set $MET_HDFLIB to point to the directory with the HDF4 library files. Also, set $MET_HDFEOS to point to the main HDF EOS directory, or set $MET_HDFEOSINC to point to the directory with the HDF EOS include files and set $MET_HDFEOSLIB to point to the directory with the HDF EOS library files.