interrupt, save

On keyboard interrupt in the regular flow of downloading the collected images of this session and of last session are saved so as not to destroy the archive accidentally this way.
If an item is added to the new collection, it is removed from the old one.
If a save is being dumped (uncleanly saved because of KB interrupt), the old collection is appended to the new one.
Upon loading the returned string is split to enable removing of the old items.

4grab.py

@@ -30,6 +30,7 @@ import util
 import download
 import progressbar
 import sorter
+import backend
 
 config._optioncreator = raw_input_with_default
 
@@ -202,6 +203,9 @@ if __name__ == "__main__":
             print "Failed:     ", failed
             print "Total:      ", total
         except KeyboardInterrupt:
+            be = backend.Backend()
+            be.save(True) # Make sure that the downloaded images are saved anyway
+
             print
             print "So you don't want these images? Fine! I'll stop then."
             util.log(util.LogType.Err, "Quit on user request")

backend.py

@@ -19,6 +19,9 @@ class _Backend(object):
         return True
 
     def add(self, filename):
+        if filename in self.__collection:
+            self.__collection.remove(filename)
+
         self.__new_collection.append(filename)
 
     def check(self, filename):        
@@ -33,7 +36,10 @@ class _Backend(object):
 
         return False
 
-    def save(self):
+    def save(self, dump = False):
+        if dump:
+            self.__new_collection.extend(self.__collection)
+
         if os.path.exists(self.table):
             os.remove(self.table)
 
@@ -43,7 +49,9 @@ class _Backend(object):
 
     def load(self):
         if os.path.exists(self.table):
-            self.__collection = self.store.select(self.table, ['recno'], ['*'], ['filename'], returnType="report")
+            collection = self.store.select(self.table, ['recno'], ['*'], ['filename'], returnType="report")
+            if collection != '':
+                self.__collection = collection.split()
 
 _backend = None
 def Backend():