Makefile: Make Python interpreter configurable

For example, my default Python is 3.2, but I only have Matplotlib
installed for 2.7.  However, the default version of Python on newton
is 2.6.  Now the user can override it at invocation:

  $ make PYTHON=python2.6 all

diff --git a/Makefile b/Makefile
index 142348e7448a4f0ab921c8735f08ff43e8cffd7b..7a535c80a9599b96ee73161b87653b8fedd5cdf2 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -54,6 +54,7 @@ $(foreach PROGRAM, $(PROGRAMS), $(eval $(PROGRAM)_LIBS = -lm))
 CP = cp
 GREP = grep
 MKDIR = mkdir
+PYTHON = python2.7
 RM = rm
 TAR = tar
 
@@ -188,10 +189,10 @@ trajectories.png: trajectories.gp trajectories.data
        gnuplot "$<" > "$@"
 
 time-vs-y0-E.png: plot_image.py final-vs-y0-E.data
-       cut -d '        ' -f 1,2,3 final-vs-y0-E.data | python2.7 ./plot_image.py --xyz -t 'Time vs impact parameter and energy' -o "$@"
+       cut -d '        ' -f 1,2,3 final-vs-y0-E.data | $(PYTHON) ./plot_image.py --xyz -t 'Time vs impact parameter and energy' -o "$@"
 
 angle-vs-y0-E.png: plot_image.py final-vs-y0-E.data
-       cut -d '        ' -f 1,2,4 final-vs-y0-E.data | python2.7 ./plot_image.py --xyz -t 'Angle vs impact parameter and energy' -o "$@"
+       cut -d '        ' -f 1,2,4 final-vs-y0-E.data | $(PYTHON) ./plot_image.py --xyz -t 'Angle vs impact parameter and energy' -o "$@"
 
 # Pattern rule for compiling object files from C++ source
 # There is an implicit rule for this in GNU make