fix representation of empty variables/linexpressions

Author: FabianHofmann

doc/release_notes.rst

@@ -1,8 +1,10 @@
 Release Notes
 =============
 
-.. Upcoming Release
-.. ----------------
+Upcoming Release
+----------------
+
+* Fix representation of empty variables and linear expressions.
 
 
 Version 0.1.3

linopy/expressions.py

@@ -226,6 +226,9 @@ def __repr__(self):
         truncate = nexprs > max_print
         coords = self.unravel_coords(to_print)
 
+        if not self.size:
+            return f"{header}\nNone"
+
         # loop over all values to print
         coord_strings = []
         expr_strings = []

linopy/variables.py

@@ -229,6 +229,9 @@ def __repr__(self):
             labels = np.ravel(self.labels.values)
             coords = [[c.item() for c in self.coords.values()]]
 
+        if not self.size:
+            return f"{header}\nNone"
+
         coord_strings = []
         var_strings = []
         bound_strings = []

test/test_repr.py

@@ -131,6 +131,12 @@ def test_constraint_repr():
         repr(con)
 
 
+def test_empty_repr():
+    repr(u.loc[[]])
+    repr(lu.sel(dim_0=[]))
+    repr(lu.sel(dim_0=[]) >= 0)
+
+
 def test_print_options():
     for o in [v, lv, cv_, cv]:
         default_repr = repr(o)