add to_file method to weights to wrap io.FileIO.open

Author: ljwolf

libpysal/weights/tests/test_weights.py

@@ -254,6 +254,12 @@ def test_connected_components(self):
         disco = W(disco)
         assert disco.n_components == 2
 
+    def test_roundtrip_write(self):
+        self.w.to_file('./tmp.gal')
+        new = W.from_file('./tmp.gal')
+        np.testing.assert_array_equal(self.w.sparse.toarray(), 
+                                      new.sparse.toarray())
+
 class Test_WSP_Back_To_W(unittest.TestCase):
     # Test to make sure we get back to the same W functionality
     def setUp(self):

libpysal/weights/weights.py

@@ -174,10 +174,48 @@ def _reset(self):
         """
         self._cache = {}
 
+    def to_file(self, path='', format=None):
+        """
+        Write a weights to a file. The format is guessed automatically 
+        from the path, but can be overridden with the format argument. 
+
+        See libpysal.io.FileIO for more information. 
+
+        Arguments
+        ---------
+        path    :   string
+                    location to save the file
+        format  :   string
+                    string denoting the format to write the weights to. 
+
+
+        Returns
+        -------
+        None
+        """
+        f = popen(dataPath=path, mode='w', dataFormat=format)
+        f.write(self)
+        f.close()
+        
+
     @classmethod
-    def from_file(cls, path='', format=None, **kwargs):
+    def from_file(cls, path='', format=None):
+        """
+        Read a weights file into a W object. 
+
+        Arguments
+        ---------
+        path    :   string
+                    location to save the file
+        format  :   string
+                    string denoting the format to write the weights to. 
+
+        Returns
+        -------
+        W object
+        """
         f = popen(dataPath=path, mode='r', dataFormat=format)
-        w = f.read(**kwargs)
+        w = f.read()
         f.close()
         return w