Added new terror 'C' (closest).

Source formatted with black.  Make sure black is installed
in venv.

pip install black flake8 pyflakes pylint

.vscode/settings.json

@@ -0,0 +1,7 @@
+{
+    "editor.formatOnSave": true,
+    "editor.formatOnPaste": true,
+    "python.formatting.provider": "black",
+    "python.pythonPath": "bin/python3",
+    "python.linting.enabled": true
+}

galaxy.py

@@ -57,7 +57,9 @@ class GameData(object):
     def special_ports(self):
         """ Save the special class ports 0, 9 """
         return {
-            p: self.ports[p] for p in self.ports if 'class' in self.ports[p] and self.ports[p]["class"] in (0, 9)
+            p: self.ports[p]
+            for p in self.ports
+            if "class" in self.ports[p] and self.ports[p]["class"] in (0, 9)
         }
 
     def display(self):
@@ -288,8 +290,12 @@ class GameData(object):
             return True
 
         cargo_index = cargo_to_index[cargo]
-        if port["port"] in ('Special', 'StarDock'):
-            log.warn("port_buying( {0}, {1}): not buying (is {2})".format(sector, cargo, port['port']))
+        if port["port"] in ("Special", "StarDock"):
+            log.warn(
+                "port_buying( {0}, {1}): not buying (is {2})".format(
+                    sector, cargo, port["port"]
+                )
+            )
             return False
         if port["port"][cargo_index] == "S":
             log.warn("port_buying( {0}, {1}): not buying cargo".format(sector, cargo))
@@ -346,7 +352,7 @@ class GameData(object):
         # Given the port settings, can we trade between these?
         if port1 == port2:
             return False
-        if port1 in ('Special', 'StarDock') or port2 in ('Special', 'StarDock'):
+        if port1 in ("Special", "StarDock") or port2 in ("Special", "StarDock"):
             return False
 
         p1 = [c for c in port1]
@@ -445,6 +451,81 @@ class GameData(object):
             GameData.port_show_part(warp, warp_port),
         )
 
+    def find_nearest_tradepairs(self, sector: int, obj):
+        """ find nearest tradepair 
+
+        When do we use good?  When do we use ok?
+        """
+        searched = set()
+        if sector not in self.warps:
+            log.warn(":Sector {0} not in warps.".format(sector))
+            obj.target_sector = None
+            return None
+
+        # Start with the current sector
+        look = set((sector,))
+
+        while len(look) > 0:
+            log.warn("Searched [{0}]".format(searched))
+            log.warn("Checking [{0}]".format(look))
+            for s in look:
+                if s in self.ports:
+                    # Ok, there's a port at least
+                    sp = self.ports[s]
+                    if sp["port"] in ("Special", "StarDock"):
+                        continue
+                    if self.port_burnt(sp):
+                        continue
+                    if "class" not in sp:
+                        continue
+                    sc = sp["class"]
+
+                    log.warn("{0} has warps {1}".format(s, self.warps[s]))
+
+                    # Ok, check for tradepairs.
+                    for w in self.warps[s]:
+                        if not w in self.warps:
+                            continue
+                        if not s in self.warps[w]:
+                            continue
+                        if not w in self.ports:
+                            continue
+
+                        # Ok, has possible port
+                        cp = self.ports[w]
+                        if cp["port"] in ("Special", "StarDock"):
+                            continue
+                        if self.port_burnt(cp):
+                            continue
+                        if "class" not in cp:
+                            continue
+                        cc = cp["class"]
+                        log.warn("{0} {1} - {2} {3}".format(s, sc, w, cc))
+                        if sc in (1, 5) and cc in (2, 4):
+                            # Good!
+                            log.warn("GOOD: {0}".format(s))
+                            obj.target_sector = s
+                            return s
+                        if sc in (2, 4) and cc in (1, 5):
+                            # Good!
+                            log.warn("GOOD: {0}".format(s))
+                            obj.target_sector = s
+                            return s
+                        # What about "OK" pairs?
+
+            # Ok, not found here.
+            searched.update(look)
+            step_from = look
+            look = set()
+            for s in step_from:
+                if s in self.warps:
+                    look.update(self.warps[s])
+            # Look only contains warps we haven't searched
+            look = look.difference(searched)
+            yield
+        obj.target_sector = None
+        return None
+
     def find_nearest_selling(
         self, sector: int, selling: str, at_least: int = 100
     ) -> int:
@@ -474,7 +555,7 @@ class GameData(object):
                 if s in self.ports:
                     # Ok, possibly?
                     sp = self.ports[s]
-                    if sp['port'] in ('Special', 'StarDock'):
+                    if sp["port"] in ("Special", "StarDock"):
                         continue
                     if sp["port"][s_pos] == "S":
                         # Ok, they are selling!