Added Workflow.get_data_file_name() which returns the full path to a given

data file, or None if the file does not exist. This is tested in the test
workflow.

workflows/test_workflow.py

@@ -17,6 +17,7 @@ class TestWorkflow (workflow.Workflow):
 
         load = workflow.Stage('load', 'Load Data')
         load.add_function(CelFileImportFunction())
+        load.add_function(DataLoadTestFunction(self))
         load.add_function(TestDataFunction())
         load.add_function(DatasetLoadFunction())
         load.add_function(SelectFunction())
@@ -257,6 +258,22 @@ class CelFileImportFunction(workflow.Function):
             chooser.destroy()
 
 
+class DataLoadTestFunction(workflow.Function):
+    def __init__(self, wf):
+        workflow.Function.__init__(self, 'datadirload', 'Load from datadir')
+        self._wf = wf
+    
+    def run(self):
+        print self._wf.get_data_file_name('smoker-x.ftsv')
+        fn = self._wf.get_data_file_name('smoker-x.ftsv')
+        if fn:
+            fd = open(fn)
+            ds = dataset.read_ftsv(fd)
+            return [ds]
+        else:
+            print "Cannot find file %s" % fn
+            return []
+
 class PCAFunction(workflow.Function):
     """Generic PCA function."""
     def __init__(self, wf):