getting Ant build error: Cannot run program "python"

Question

This is the build file:

<exec executable="python" failonerror="true">
  <arg line="${installer.izpack.dir}/utils/wrappers/izpack2exe/izpack2exe.py"/>
  <arg line="--file=${basedir}/installer/EasyIT-installer.jar"/>
  <arg line="--output=${basedir}/installer/EasyIT-installer.exe"/>
  <arg line="--no-upx"/>
</exec>

And the output:

BUILD FAILED
E:\Java Projects\Spark Projects\EastIT - Copy\build\build.xml:873: Execute failed: java.io.IOException: Cannot run program "python" (in directory "E:\Java Projects\Spark Projects\EastIT - Copy"): CreateProcess error=2, The system cannot find the file specified
        at java.lang.ProcessBuilder.start(ProcessBuilder.java:1029)
        at java.lang.Runtime.exec(Runtime.java:615)
        at org.apache.tools.ant.taskdefs.Execute$Java13CommandLauncher.exec(Execute.java:8 62)
        at org.apache.tools.ant.taskdefs.Execute.launch(Execute.java:481)
        at org.apache.tools.ant.taskdefs.Execute.execute(Execute.java:495)
        at org.apache.tools.ant.taskdefs.ExecTask.runExecute(ExecTask.java:631)
        at org.apache.tools.ant.taskdefs.ExecTask.runExec(ExecTask.java:672)
        at org.apache.tools.ant.taskdefs.ExecTask.execute(ExecTask.java:498)
        at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:291)
        at sun.reflect.GeneratedMethodAccessor15.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.ja va:43)
        at java.lang.reflect.Method.invoke(Method.java:601)
        at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106)
        at org.apache.tools.ant.Task.perform(Task.java:348)
        at org.apache.tools.ant.Target.execute(Target.java:392)
        at org.apache.tools.ant.Target.performTasks(Target.java:413)
        at org.apache.tools.ant.Project.executeSortedTargets(Project.java:1399)
        at org.apache.tools.ant.Project.executeTarget(Project.java:1368)
        at org.apache.tools.ant.helper.DefaultExecutor.executeTargets(DefaultExecutor.java :41)
        at org.apache.tools.ant.Project.executeTargets(Project.java:1251)
        at org.apache.tools.ant.Main.runBuild(Main.java:811)
        at org.apache.tools.ant.Main.startAnt(Main.java:217)
        at org.apache.tools.ant.launch.Launcher.run(Launcher.java:280)
        at org.apache.tools.ant.launch.Launcher.main(Launcher.java:109)
Caused by: java.io.IOException: CreateProcess error=2, The system cannot find the file specified
        at java.lang.ProcessImpl.create(Native Method)
        at java.lang.ProcessImpl.<init>(ProcessImpl.java:189)
        at java.lang.ProcessImpl.start(ProcessImpl.java:133)
        at java.lang.ProcessBuilder.start(ProcessBuilder.java:1021)
        ... 23 more


Total time: 50 seconds

Solution

Make sure that python is in the PATH where you're running the build, or specify an absolute path to your python executable in the exec task.

Review the docs for the exec task for any specific instructions on using windows vs. not-windows. Note that your specific error is mentioned there:

A common problem is not having the executable on the PATH. In case you get an error message Cannot run program "...":CreateProcess error=2. The system cannot find the path specified. have a look at your PATH variable. Just type the command directly on the command line and if Windows finds it, Ant should do it too. (Otherwise ask on the user mailinglist for help.) If Windows can not execute the program add the directory of the programm to the PATH (set PATH=%PATH%;dirOfProgram) or specify the absolute path in the executable attribute in your buildfile.