MacPython and Gnuplot in MacOS X

Scientific use of Python requires at a minimum Numerical Python and a simple way to generate plots. There are several ways to do this under MacOS X. Here I describe a simple approach using MacPython and Gnuplot.

You can instead use the Unix versions of Python and many other programs. This is actually easier than what I describe below, as long as you use the Fink project. However this approach requires extensive downloads, including all of X-windows. On the other hand, it makes the entire world of open-source Unix software available to you, so it may well be worth the download time. On the other other hand, MacPython is is a very elegant Mac-centric program.

So here instead is a relatively small set of downloads which gives a functioning Python (MacPython), a nice development environment (PythonIDE), Numerical Python, and plotting (using Gnuplot). Pretty much everything I want except for Scipy. The following instructions use the terminal application, which is located in /Applications/Utilities.

• Download MacPython 2.3. (I downloaded a version that worked for me in case something breaks in a later release. Get it here.) The download is a disk image which is mounted on your desktop. Open it and double-click the pkg file to install.

• You may need to change some file ownerships before continuing. Execute
  
  sudo chown USERNAME /Library/Frameworks/Python.framework/Versions/2.3/lib/python2.3/site-packages
  
  (all one line regardless of how it appears in your browser) in a terminal window. Here USERNAME is your user name.

• Open the MacPython folder in your Applications folder and start PythonIDE, a nice Python development environment. Select File->PackageManager. Select Numeric-22.0-binary, uncheck the box "For current user only" and click Install.

• Download Gnuplot. (I downloaded a version which is available here.) Open a terminal window and change directory ("cd") to wherever you downloaded. Then issue the commands
  
  uncompress gnuplot_binaries.pax
  sudo pax -rf gnuplot_binaries.pax
  
  This installs gnuplot in /usr/local/bin.

• Download gnuplot.py. (I downloaded a version which is available here.) Open a terminal window and change directory ("cd") to wherever you downloaded. Then issue the commands
  
  gunzip gnuplot-py-1.6-1.tar (if the file was not uncompressed during download)
  tar -xf gnuplot-py-1.6-1.tar (if the file was not untarred during download)
  cd gnuplot-py-1.6
  /usr/local/bin/python setup.py install

• You need to fix one file which this installs. In a terminal change directory by issuing the command
  
  cd /Library/Frameworks/Python.framework/Versions/2.3/lib/python2.3/site-packages/Gnuplot
  
  Edit the file gp_macosx.py (perhaps using "pico gp_macosx.py"), changing the line
  
  gnuplot_command = 'gnuplot'
  
  to
  
  gnuplot_command = '/usr/local/bin/gnuplot'
  
  
• Download Aquaterm. (I downloaded an older version which is available here.) If necessary navigate to the downloaded file and issue these commands within a terminal:
  gunzip aquaterm-0.3.2.tar (if the file was not uncompressed during download)
  tar -xf aquaterm-0.3.2.tar (if the file was not untarred during download)
  
  Copy or drag the application Aquaterm from folder AQT to your Applications folder.
  
  
• To test Gnuplot, start PythonIDE. Open the file
  
  /Library/Frameworks/Python.framework/Versions/2.3/lib/python2.3/site-packages/Gnuplot/demo.py
  
  The file opens in PythonIDE's script editor. Look at the file to see typical uses of gnuplot.py. One change is needed. Scroll down, and just after the line
  g = Gnuplot.Gnuplot(debug=1)
  add the following:
  g('set terminal aqua') (Indent exactly as the preceding line.)
  Click the little black triangle on the upper right edge of the PythonIDE window that opens, and choose "Run as __main__". Then click "Run all". Wait a while before clicking "OK".

• The examples in demo.py all plot in the same window. You can open plots in multiple windows using:
  g('set terminal aqua 1')
  g.plot(...)
  g('set terminal aqua 2')
  g.plot(...)
  
  
  M.D. Johnson, August 2003