Fixes related to CSV exporter:

- CSV headers include data names, if available
  - Exporter correctly handles items with no data
  - pg.plot() avoids creating empty data item
  - removed call to reduce() from exporter; not available in python 3
  - Gave .name() methods to PlotDataItem, PlotCurveItem, and ScatterPlotItem

examples/Plotting.py

@@ -27,9 +27,9 @@ pg.setConfigOptions(antialias=True)
 p1 = win.addPlot(title="Basic array plotting", y=np.random.normal(size=100))
 
 p2 = win.addPlot(title="Multiple curves")
-p2.plot(np.random.normal(size=100), pen=(255,0,0))
-p2.plot(np.random.normal(size=100)+5, pen=(0,255,0))
-p2.plot(np.random.normal(size=100)+10, pen=(0,0,255))
+p2.plot(np.random.normal(size=100), pen=(255,0,0), name="Red curve")
+p2.plot(np.random.normal(size=110)+5, pen=(0,255,0), name="Blue curve")
+p2.plot(np.random.normal(size=120)+10, pen=(0,0,255), name="Green curve")
 
 p3 = win.addPlot(title="Drawing with points")
 p3.plot(np.random.normal(size=100), pen=(200,200,200), symbolBrush=(255,0,0), symbolPen='w')

pyqtgraph/__init__.py

@@ -292,7 +292,8 @@ def plot(*args, **kargs):
             dataArgs[k] = kargs[k]
         
     w = PlotWindow(**pwArgs)
-    w.plot(*args, **dataArgs)
+    if len(args) > 0 or len(dataArgs) > 0:
+        w.plot(*args, **dataArgs)
     plots.append(w)
     w.show()
     return w

pyqtgraph/exporters/CSVExporter.py

@@ -33,8 +33,14 @@ class CSVExporter(Exporter):
         data = []
         header = []
         for c in self.item.curves:
-            data.append(c.getData())
-            header.extend(['x', 'y'])
+            cd = c.getData()
+            if cd[0] is None:
+                continue
+            data.append(cd)
+            name = ''
+            if hasattr(c, 'implements') and c.implements('plotData') and c.name() is not None:
+                name = c.name().replace('"', '""') + '_'
+            header.extend(['"'+name+'x"', '"'+name+'y"'])
 
         if self.params['separator'] == 'comma':
             sep = ','
@@ -44,7 +50,7 @@ class CSVExporter(Exporter):
         fd.write(sep.join(header) + '\n')
         i = 0
         numFormat = '%%0.%dg' % self.params['precision']
-        numRows = reduce(max, [len(d[0]) for d in data])
+        numRows = max([len(d[0]) for d in data])
         for i in range(numRows):
             for d in data:
                 if i < len(d[0]):

pyqtgraph/graphicsItems/PlotCurveItem.py

@@ -65,7 +65,7 @@ class PlotCurveItem(GraphicsObject):
             'brush': None,
             'stepMode': False,
             'name': None,
-            'antialias': pg.getConfigOption('antialias'),\
+            'antialias': pg.getConfigOption('antialias'),
             'connect': 'all',
             'mouseWidth': 8, # width of shape responding to mouse click
         }
@@ -78,6 +78,9 @@ class PlotCurveItem(GraphicsObject):
             return ints
         return interface in ints
     
+    def name(self):
+        return self.opts.get('name', None)
+    
     def setClickable(self, s, width=None):
         """Sets whether the item responds to mouse clicks.
         

pyqtgraph/graphicsItems/PlotDataItem.py

@@ -170,6 +170,9 @@ class PlotDataItem(GraphicsObject):
             return ints
         return interface in ints
     
+    def name(self):
+        return self.opts.get('name', None)
+    
     def boundingRect(self):
         return QtCore.QRectF()  ## let child items handle this
 

pyqtgraph/graphicsItems/PlotItem/PlotItem.py

@@ -514,7 +514,9 @@ class PlotItem(GraphicsWidget):
         if 'ignoreBounds' in kargs:
             vbargs['ignoreBounds'] = kargs['ignoreBounds']
         self.vb.addItem(item, *args, **vbargs)
+        name = None
         if hasattr(item, 'implements') and item.implements('plotData'):
+            name = item.name()
             self.dataItems.append(item)
             #self.plotChanged()
             
@@ -547,7 +549,7 @@ class PlotItem(GraphicsWidget):
             #c.connect(c, QtCore.SIGNAL('plotChanged'), self.plotChanged)
             #item.sigPlotChanged.connect(self.plotChanged)
             #self.plotChanged()
-        name = kargs.get('name', getattr(item, 'opts', {}).get('name', None))
+        #name = kargs.get('name', getattr(item, 'opts', {}).get('name', None))
         if name is not None and hasattr(self, 'legend') and self.legend is not None:
             self.legend.addItem(item, name=name)
             

pyqtgraph/graphicsItems/ScatterPlotItem.py

@@ -234,6 +234,7 @@ class ScatterPlotItem(GraphicsObject):
             'pxMode': True, 
             'useCache': True,  ## If useCache is False, symbols are re-drawn on every paint. 
             'antialias': pg.getConfigOption('antialias'),
+            'name': None,
         }   
         
         self.setPen(200,200,200, update=False)
@@ -281,6 +282,8 @@ class ScatterPlotItem(GraphicsObject):
         *antialias*            Whether to draw symbols with antialiasing. Note that if pxMode is True, symbols are 
                                always rendered with antialiasing (since the rendered symbols can be cached, this 
                                incurs very little performance cost)
+        *name*                 The name of this item. Names are used for automatically
+                               generating LegendItem entries and by some exporters.
         ====================== ===============================================================================================
         """
         oldData = self.data  ## this causes cached pixmaps to be preserved while new data is registered.
@@ -410,6 +413,9 @@ class ScatterPlotItem(GraphicsObject):
             return ints
         return interface in ints
     
+    def name(self):
+        return self.opts.get('name', None)
+    
     def setPen(self, *args, **kargs):
         """Set the pen(s) used to draw the outline around each spot. 
         If a list or array is provided, then the pen for each spot will be set separately.