Clean up previous PR

A few micro-optimizations in the loops checking for changed values.
And use suppress() to ignore exceptions

src/calibre/db/write.py

@@ -18,6 +18,8 @@ from calibre.utils.date import (
 from calibre.utils.localization import canonicalize_lang
 from calibre.utils.icu import strcmp
 
+missing = object()
+
 # Convert data into values suitable for the db {{{
 
 
@@ -196,10 +198,10 @@ def one_one_in_books(book_id_val_map, db, field, *args):
     # We can't do this for the cover because the file might change without
     # the presence-of-cover flag changing
     if field.name != 'cover':
-        book_id_val_map = {k:v for k, v in iteritems(book_id_val_map)
-            if v != field.table.book_col_map.get(k, None)}
+        g = field.table.book_col_map.get
+        book_id_val_map = {k:v for k, v in book_id_val_map.items() if v != g(k, missing)}
     if book_id_val_map:
-        sequence = ((sqlite_datetime(v), k) for k, v in iteritems(book_id_val_map))
+        sequence = ((sqlite_datetime(v), k) for k, v in book_id_val_map.items())
         db.executemany(
             'UPDATE books SET %s=? WHERE id=?'%field.metadata['column'], sequence)
         field.table.book_col_map.update(book_id_val_map)
@@ -215,15 +217,15 @@ def set_title(book_id_val_map, db, field, *args):
     ans = one_one_in_books(book_id_val_map, db, field, *args)
     # Set the title sort field if the title changed
     field.title_sort_field.writer.set_books(
-        {k:title_sort(v) for k, v in iteritems(book_id_val_map) if k in ans}, db)
+        {k:title_sort(v) for k, v in book_id_val_map.items() if k in ans}, db)
     return ans
 
 
 def one_one_in_other(book_id_val_map, db, field, *args):
     'Set a one-one field in the non-books table, like comments'
     # Ignore those items whose value is the same as the current value
-    book_id_val_map = {k:v for k, v in iteritems(book_id_val_map)
-        if v != field.table.book_col_map.get(k, None)}
+    g = field.table.book_col_map.get
+    book_id_val_map = {k:v for k, v in iteritems(book_id_val_map) if v != g(k, missing)}
     deleted = tuple((k,) for k, v in iteritems(book_id_val_map) if v is None)
     if deleted:
         db.executemany('DELETE FROM %s WHERE book=?'%field.metadata['table'],
@@ -247,7 +249,7 @@ def custom_series_index(book_id_val_map, db, field, *args):
         if sidx is None:
             sidx = 1.0
         if ids:
-            if field.table.book_col_map.get(book_id, None) != sidx:
+            if field.table.book_col_map.get(book_id, missing) != sidx:
                 sequence.append((sidx, book_id, ids[0]))
                 field.table.book_col_map[book_id] = sidx
         else:
@@ -433,11 +435,11 @@ def many_many(book_id_val_map, db, field, allow_case_change, *args):
                         field.author_sort_field.writer.set_books({book_id:new_sort}, db)
 
     book_id_item_id_map = {k:tuple(val_map[v] for v in vals)
-                           for k, vals in iteritems(book_id_val_map)}
+                           for k, vals in book_id_val_map.items()}
 
     # Ignore those items whose value is the same as the current value
-    book_id_item_id_map = {k:v for k, v in iteritems(book_id_item_id_map)
-        if v != table.book_col_map.get(k, tuple())}
+    g = table.book_col_map.get
+    book_id_item_id_map = {k:v for k, v in book_id_item_id_map.items() if v != g(k, missing)}
     dirtied |= set(book_id_item_id_map)
 
     # Update the book->col and col->book maps
@@ -495,8 +497,8 @@ def many_many(book_id_val_map, db, field, allow_case_change, *args):
 
 def identifiers(book_id_val_map, db, field, *args):  # {{{
     # Ignore those items whose value is the same as the current value
-    book_id_val_map = {k:v for k, v in iteritems(book_id_val_map)
-        if v != field.table.book_col_map.get(k, None)}
+    g = field.table.book_col_map.get
+    book_id_val_map = {k:v for k, v in book_id_val_map.items() if v != g(k, missing)}
 
     table = field.table
     updates = set()

src/calibre/utils/formatter_functions.py

@@ -15,6 +15,7 @@ __docformat__ = 'restructuredtext en'
 import inspect, re, traceback, numbers
 from datetime import datetime, timedelta
 from math import trunc, floor, ceil, modf
+from contextlib import suppress
 
 from calibre import human_readable, prints
 from calibre.constants import DEBUG
@@ -1266,12 +1267,10 @@ class BuiltinAnnotationCount(BuiltinFormatterFunction):
                       'This function works only in the GUI.')
 
     def evaluate(self, formatter, kwargs, mi, locals):
-        try:
+        with suppress(Exception):
             from calibre.gui2.ui import get_gui
             c = get_gui().current_db.new_api.annotation_count_for_book(mi.id)
             return '' if c == 0 else unicode_type(c)
-        except:
-            pass
         return _('This function can be used only in the GUI')
 
 
@@ -1285,12 +1284,10 @@ class BuiltinIsMarked(BuiltinFormatterFunction):
                       "marks. Returns '' if the book is not marked.")
 
     def evaluate(self, formatter, kwargs, mi, locals):
-        try:
+        with suppress(Exception):
             from calibre.gui2.ui import get_gui
             c = get_gui().current_db.data.get_marked(mi.id)
             return c if c else ''
-        except:
-            pass
         return _('This function can be used only in the GUI')
 
 
@@ -1758,12 +1755,10 @@ class BuiltinVirtualLibraries(BuiltinFormatterFunction):
                       'column\'s value in your save/send templates')
 
     def evaluate(self, formatter, kwargs, mi, locals_):
-        try:
+        with suppress(Exception):
             from calibre.gui2.ui import get_gui
             a = get_gui().current_db.data.get_virtual_libraries_for_books((mi.id,))
             return ', '.join(a[mi.id])
-        except:
-            pass
         return _('This function can be used only in the GUI')
 
 
@@ -1861,7 +1856,7 @@ class BuiltinConnectedDeviceName(BuiltinFormatterFunction):
                       "'carda' and 'cardb'. This function works only in the GUI.")
 
     def evaluate(self, formatter, kwargs, mi, locals, storage_location):
-        try:
+        with suppress(Exception):
             # Do the import here so that we don't entangle the GUI when using
             # command line functions
             from calibre.gui2.ui import get_gui
@@ -1877,11 +1872,9 @@ class BuiltinConnectedDeviceName(BuiltinFormatterFunction):
                 if storage_location not in info:
                     return ''
                 return info[storage_location]['device_name']
-            except:
+            except Exception:
                 traceback.print_exc()
                 raise
-        except:
-            pass
         return _('This function can be used only in the GUI')
 
 
@@ -1897,7 +1890,7 @@ class BuiltinConnectedDeviceUUID(BuiltinFormatterFunction):
                       "the GUI.")
 
     def evaluate(self, formatter, kwargs, mi, locals, storage_location):
-        try:
+        with suppress(Exception):
             # Do the import here so that we don't entangle the GUI when using
             # command line functions
             from calibre.gui2.ui import get_gui
@@ -1913,11 +1906,9 @@ class BuiltinConnectedDeviceUUID(BuiltinFormatterFunction):
                 if storage_location not in info:
                     return ''
                 return info[storage_location]['device_store_uuid']
-            except:
+            except Exception:
                 traceback.print_exc()
                 raise
-        except:
-            pass
         return _('This function can be used only in the GUI')