setContextAsView function; raise cusom error when no data loaded into…

… View; Spec documentation

doc/source/guide/spec.rst

@@ -97,3 +97,29 @@ So far, we have seen examples of how to express existing use cases based on `lux
 .. code-block:: python
     
     df.setContext([lux.Spec(attribute='AverageCost', channel='y')])
+
+Specifying wildcards
+~~~~~~~~~~~~~~~~~~~~~
+
+Let's say that you are interested in *any* attribute with respect to `AverageCost`. Lux support *wildcards* (based on .. _CompassQL: https://idl.cs.washington.edu/papers/compassql/), which specifies the enumeration of any possible attribute or values that satisfies the provided constraints.
+
+.. code-block:: python
+    
+    df.setContext(['AverageCost',lux.Spec('?')])
+
+The space of enumeration can be narrowed based on constraints. For example, you might only be interested in looking at scatterplots of `AverageCost` with respect to quantitative attributes. 
+
+.. code-block:: python
+    
+    df.setContext(['AverageCost',lux.Spec('?',dataType='quantitative')])
+
+The enumeration specifier can also be placed on the value field. For example, you might be interested in looking at how the distribution of `AverageCost` varies for all possible values of `Geography`.
+
+.. code-block:: python
+    
+    df.setContext(['AverageCost','Geography=?')])
+or 
+
+.. code-block:: python
+
+    df.setContext(['AverageCost',lux.Spec(attribute='Geography',filterOp='=',value='?')])

lux/compiler/Compiler.py

@@ -1,5 +1,5 @@
 from lux.context import Spec
-from typing import List, Dict
+from typing import List, Dict, Union
 from lux.view.View import View
 from lux.luxDataFrame.LuxDataframe import LuxDataFrame
 from lux.view.ViewCollection import ViewCollection
@@ -43,7 +43,8 @@ def compile(ldf: LuxDataFrame,specLst:List[Spec], viewCollection: ViewCollection
 		if (enumerateCollection):
 			viewCollection = Compiler.enumerateCollection(specLst,ldf)
 		viewCollection = Compiler.expandUnderspecified(ldf, viewCollection)  # autofill data type/model information
-		viewCollection = Compiler.removeAllInvalid(viewCollection) # remove invalid views from collection
+		if len(viewCollection)>1: 
+			viewCollection = Compiler.removeAllInvalid(viewCollection) # remove invalid views from collection
 		for view in viewCollection:
 			Compiler.determineEncoding(ldf, view)  # autofill viz related information
 		return viewCollection
@@ -133,7 +134,7 @@ def expandUnderspecified(ldf, viewCollection):
 		return views
 
 	@staticmethod
-	def removeAllInvalid(viewCollection):
+	def removeAllInvalid(viewCollection:ViewCollection) -> ViewCollection:
 		"""
 		Given an expanded view collection, remove all views that are invalid.
 		Currently, the invalid views are ones that contain temporal by temporal attributes or overlapping attributes.

lux/luxDataFrame/LuxDataframe.py

@@ -1,5 +1,6 @@
 import pandas as pd
 from lux.context.Spec import Spec
+from lux.view.View import View
 from lux.view.ViewCollection import ViewCollection
 from lux.utils.utils import checkImportLuxWidget
 #import for benchmarking
@@ -47,7 +48,7 @@ def setExecutorType(self, exe):
         if (exe =="SQL"):
             import pkgutil
             if (pkgutil.find_loader("psycopg2") is None):
-                raise Exception("psycopg2 is not installed. Run `pip install psycopg2' to install psycopg2 to enable the Postgres connection.")
+                raise ImportError("psycopg2 is not installed. Run `pip install psycopg2' to install psycopg2 to enable the Postgres connection.")
             else:
                 import psycopg2
             from lux.executor.SQLExecutor import SQLExecutor
@@ -87,6 +88,18 @@ def setContext(self,context:typing.List[typing.Union[str,Spec]]):
         """        
         self.context = context
         self._refreshContext()
+    def setContextAsView(self,view:View):
+        """
+        Set context of the dataframe as the View
+
+        Parameters
+        ----------
+        view : View
+            [description]
+        """        
+        self.context = view.specLst
+        self._refreshContext()
+
     def clearContext(self):
         self.context = []
         self.viewCollection = []

lux/view/View.py

@@ -1,4 +1,5 @@
 from __future__ import annotations
+from typing import List
 from lux.context.Spec import Spec
 from lux.utils.utils import checkImportLuxWidget
 class View:
@@ -20,21 +21,25 @@ def __repr__(self):
 		filter_spec = None
 		channels, additional_channels = [], []
 		for spec in self.specLst:
-			if spec.value != "":
-				filter_spec = spec
-			if spec.attribute != "":
-				if spec.aggregation != "":
-					attribute = spec.aggregation.upper() + "(" + spec.attribute + ")"
-				elif spec.binSize > 0:
-					attribute = "BIN(" + spec.attribute + ")"
-				else:
-					attribute = spec.attribute
-				if spec.channel == "x":
-					channels.insert(0, [spec.channel, attribute])
-				elif spec.channel == "y":
-					channels.insert(1, [spec.channel, attribute])
-				elif spec.channel != "":
-					additional_channels.append([spec.channel, attribute])
+
+			if hasattr(spec,"value"):
+				if spec.value != "":
+					filter_spec = spec
+			if hasattr(spec,"attribute"):
+				if spec.attribute != "":
+					if spec.aggregation != "":
+						attribute = spec.aggregation.upper() + "(" + spec.attribute + ")"
+					elif spec.binSize > 0:
+						attribute = "BIN(" + spec.attribute + ")"
+					else:
+						attribute = spec.attribute
+					if spec.channel == "x":
+						channels.insert(0, [spec.channel, attribute])
+					elif spec.channel == "y":
+						channels.insert(1, [spec.channel, attribute])
+					elif spec.channel != "":
+						additional_channels.append([spec.channel, attribute])
+
 		channels.extend(additional_channels)
 		str_channels = ""
 		for channel in channels:
@@ -48,14 +53,17 @@ def _repr_html_(self):
 		from IPython.display import display
 		checkImportLuxWidget()
 		import luxWidget
-		from lux.luxDataFrame.LuxDataframe import LuxDataFrame
-		# widget  = LuxDataFrame.renderWidget(inputCurrentView=self,renderTarget="viewOnly")
-		widget =  luxWidget.LuxWidget(
-                currentView= LuxDataFrame.currentViewToJSON([self]),
-                recommendations=[],
-                context={}
-            )
-		display(widget)
+		if (self.data is None):
+			raise Exception("No data populated in View. Use the 'load' function (e.g., view.load(df)) to populate the view with a data source.")
+		else:
+			from lux.luxDataFrame.LuxDataframe import LuxDataFrame
+			# widget  = LuxDataFrame.renderWidget(inputCurrentView=self,renderTarget="viewOnly")
+			widget =  luxWidget.LuxWidget(
+					currentView= LuxDataFrame.currentViewToJSON([self]),
+					recommendations=[],
+					context={}
+				)
+			display(widget)
 	def getAttrByAttrName(self,attrName):
 		return list(filter(lambda x: x.attribute == attrName, self.specLst))