How to build PyNGL from source code

PyNGL can only be built on UNIX systems. It has been successfully built on systems running Linux (32 or 64-bit), MacOSX (PPC or Intel), Windows/Cygwin, Suns using native compilers, IBMs running AIX (32 or 64-bit), and SGIs running IRIX.

This document covers what external software packages you need for PyNGL and how to build them, and then finally how to build PyNGL.

For information on building PyNIO from source code, see the "build PyNIO from source code" document.

Install C and Fortran compilers
Download and build external software
Download the source code for PyNGL
Set environment variables if necessary
Execute the 'setup.py' script

Install C and Fortran compilers

You need to have an ANSI C and a Fortran 77 or Fortran 90 compiler. If you are on a MacOS, Cygwin, or Linux system, "gcc" and "gfortran" should work just fine. We've known "g95" to work as well.

Usually the gcc compiler comes with your system, sometimes as an optional install. For example, with the Macs, it's available as part of the developer's tool kit.

The gfortran compiler can be downloaded from http://gcc.gnu.org/wiki/GFortran.

Download and build external software

Once you download and install any external software to use with PyNGL, you must comply with the license of that software, regardless of PyNGL's source code license.

List of external software to install:

NCL
See the full instructions for building NCL from either source code or binary. NCL is a difficult package to build, so we recommend going the binary distribution route if possible. Don't fret if you can't get the code in $NCARG/ni/src/ncl to build; it is not needed by PyNGL.
Make sure the NCARG_ROOT environment variable is set to the root directory of where this software was installed.
X11 library
You must have the X11 library (libX11.a, libX11.so) installed on your system.
This library is usually installed as part of an X developer's package, and will reside in a directory like /usr/X11R6/lib or /usr/X11R6/lib64.
libpng
Download version 1.2.27 or later (earlier versions had a serious bug).
Once you have the libpng source code, you can build and install it with:
```
  ./configure  --with-pic --disable-shared --prefix=/usr/local 
  make all install
```
zlib - needed for both PyNGL and PyNIO.
Download version 1.2.3 or later.
Once you have the zlib source code, you can build and install it with:
```
  ./configure --prefix=/usr/local
  make all install
```

Download the source code for PyNGL

Accessing, downloading, and/or using PyNGL implies acceptance of the PyNGL source code license.

To download the PyNGL source code, follow the instructions at the URL:

http://www.pyngl.ucar.edu/Download/

The source code you download will be a single compressed tar file called something like "PyNGL-1.3.0b1.tar.gz". Move this file to a temporary directory where you have plenty of disk space (around 250 megabytes to hold all of the source code, object files, binaries, and so on). Then, uncompress and untar the file as follows:

  gunzip PyNGL-1.3.0b1.tar.gz
  tar -xvf PyNGL-1.3.0b1.tar

The above steps will create a directory called "PyNGL-1.3.0b1".

Set environment variables if necessary

To build PyNGL, you must set the NCARG_ROOT environment variable to the root directory of where NCL was installed.

To help PyNGL locate the png and zlib software, you may need to set the corresponding environment variables to the root directory of that installed software:

PNG_PREFIX
ZLIB_PREFIX

You only need to set one of these if the paths are all the same.

You may need to help the PyNGL installation find the location of any system Fortran libraries needed to resolve symbols between C and Fortran code. For example, "-lgfortran" is needed if you built the software with gfortran, or "-lg2c" if g77 was used, and "-lf95" for g95. Use F2CLIBS to indicate the library name (don't include the "-l", and F2CLIBS_PREFIX to point to the location. For example:

setenv F2CLIBS gfortran
setenv F2CLIBS_PREFIX /usr/local/lib

Execute the 'setup.py' script

Type:

python setup.py install

to build and install PyNGL. Go back to the "test software" section in the download section for information on testing PyNGL.

If you have problems, send email to pyngl-talk (you must be a member to post). We will add a trouble-shooting guide once we see what kind of problems people have.