diff --git a/src/calibre/db/backend.py b/src/calibre/db/backend.py
index c2beb25e2e..0194cfc2ae 100644
--- a/src/calibre/db/backend.py
+++ b/src/calibre/db/backend.py
@@ -41,8 +41,7 @@ Differences in semantics from pysqlite:
 '''
 
 
-
-class DynamicFilter(object): # {{{
+class DynamicFilter(object):  # {{{
 
     'No longer used, present for legacy compatibility'
 
@@ -57,7 +56,7 @@ class DynamicFilter(object): # {{{
         self.ids = frozenset(ids)
 # }}}
 
-class DBPrefs(dict): # {{{
+class DBPrefs(dict):  # {{{
 
     'Store preferences as key:value pairs in the db'
 
@@ -114,9 +113,10 @@ class DBPrefs(dict): # {{{
             return default
 
     def set_namespaced(self, namespace, key, val):
-        if u':' in key: raise KeyError('Colons are not allowed in keys')
-        if u':' in namespace: raise KeyError('Colons are not allowed in'
-                ' the namespace')
+        if u':' in key:
+            raise KeyError('Colons are not allowed in keys')
+        if u':' in namespace:
+            raise KeyError('Colons are not allowed in the namespace')
         key = u'namespaced:%s:%s'%(namespace, key)
         self[key] = val
 
@@ -170,7 +170,8 @@ def pynocase(one, two, encoding='utf-8'):
     return cmp(one.lower(), two.lower())
 
 def _author_to_author_sort(x):
-    if not x: return ''
+    if not x:
+        return ''
     return author_to_author_sort(x.replace('|', ','))
 
 def icu_collator(s1, s2):
@@ -239,9 +240,9 @@ def AumSortedConcatenate():
 
 # }}}
 
-class Connection(apsw.Connection): # {{{
+class Connection(apsw.Connection):  # {{{
 
-    BUSY_TIMEOUT = 2000 # milliseconds
+    BUSY_TIMEOUT = 2000  # milliseconds
 
     def __init__(self, path):
         apsw.Connection.__init__(self, path)
@@ -257,7 +258,7 @@ class Connection(apsw.Connection): # {{{
         self.createscalarfunction('title_sort', title_sort, 1)
         self.createscalarfunction('author_to_author_sort',
                 _author_to_author_sort, 1)
-        self.createscalarfunction('uuid4', lambda : str(uuid.uuid4()),
+        self.createscalarfunction('uuid4', lambda: str(uuid.uuid4()),
                 0)
 
         # Dummy functions for dynamically created filters
@@ -380,7 +381,7 @@ class DB(object):
         self.initialize_custom_columns()
         self.initialize_tables()
 
-    def initialize_prefs(self, default_prefs): # {{{
+    def initialize_prefs(self, default_prefs):  # {{{
         self.prefs = DBPrefs(self)
 
         if default_prefs is not None and not self._exists:
@@ -493,7 +494,7 @@ class DB(object):
             self.prefs.set('user_categories', user_cats)
     # }}}
 
-    def initialize_custom_columns(self): # {{{
+    def initialize_custom_columns(self):  # {{{
         with self.conn:
             # Delete previously marked custom columns
             for record in self.conn.get(
@@ -634,11 +635,11 @@ class DB(object):
 
         self.custom_data_adapters = {
                 'float': adapt_number,
-                'int':   adapt_number,
-                'rating':lambda x,d : x if x is None else min(10., max(0., float(x))),
-                'bool':  adapt_bool,
+                'int': adapt_number,
+                'rating':lambda x,d: x if x is None else min(10., max(0., float(x))),
+                'bool': adapt_bool,
                 'comments': lambda x,d: adapt_text(x, {'is_multiple':False}),
-                'datetime' : adapt_datetime,
+                'datetime': adapt_datetime,
                 'text':adapt_text,
                 'series':adapt_text,
                 'enumeration': adapt_enum
@@ -661,7 +662,7 @@ class DB(object):
 
     # }}}
 
-    def initialize_tables(self): # {{{
+    def initialize_tables(self):  # {{{
         tables = self.tables = {}
         for col in ('title', 'sort', 'author_sort', 'series_index', 'comments',
                 'timestamp', 'pubdate', 'uuid', 'path', 'cover',
@@ -866,8 +867,8 @@ class DB(object):
         Read all data from the db into the python in-memory tables
         '''
 
-        with self.conn: # Use a single transaction, to ensure nothing modifies
-                        # the db while we are reading
+        with self.conn:  # Use a single transaction, to ensure nothing modifies
+                         # the db while we are reading
             for table in self.tables.itervalues():
                 try:
                     table.read(self)
@@ -885,7 +886,7 @@ class DB(object):
             return fmt_path
         try:
             candidates = glob.glob(os.path.join(path, '*'+fmt))
-        except: # If path contains strange characters this throws an exc
+        except:  # If path contains strange characters this throws an exc
             candidates = []
         if fmt and candidates and os.path.exists(candidates[0]):
             shutil.copyfile(candidates[0], fmt_path)
@@ -954,7 +955,7 @@ class DB(object):
                         if path != dest:
                             os.rename(path, dest)
                     except:
-                        pass # Nothing too catastrophic happened, the cases mismatch, that's all
+                        pass  # Nothing too catastrophic happened, the cases mismatch, that's all
                 else:
                     windows_atomic_move.copy_path_to(path, dest)
         else:
@@ -970,7 +971,7 @@ class DB(object):
                         try:
                             os.rename(path, dest)
                         except:
-                            pass # Nothing too catastrophic happened, the cases mismatch, that's all
+                            pass  # Nothing too catastrophic happened, the cases mismatch, that's all
                 else:
                     if use_hardlink:
                         try:
@@ -1021,7 +1022,7 @@ class DB(object):
             if not os.path.exists(tpath):
                 os.makedirs(tpath)
 
-            if source_ok: # Migrate existing files
+            if source_ok:  # Migrate existing files
                 dest = os.path.join(tpath, 'cover.jpg')
                 self.copy_cover_to(current_path, dest,
                         windows_atomic_move=wam, use_hardlink=True)
@@ -1064,7 +1065,7 @@ class DB(object):
                         os.rename(os.path.join(curpath, oldseg),
                                 os.path.join(curpath, newseg))
                     except:
-                        break # Fail silently since nothing catastrophic has happened
+                        break  # Fail silently since nothing catastrophic has happened
                 curpath = os.path.join(curpath, newseg)
 
     def write_backup(self, path, raw):
diff --git a/src/calibre/db/cache.py b/src/calibre/db/cache.py
index 630757497b..0fa280d997 100644
--- a/src/calibre/db/cache.py
+++ b/src/calibre/db/cache.py
@@ -86,7 +86,7 @@ class Cache(object):
         # Assumption is that someone else will fix them if they change.
         self.field_metadata.remove_dynamic_categories()
         for user_cat in sorted(self._pref('user_categories', {}).iterkeys(), key=sort_key):
-            cat_name = '@' + user_cat # add the '@' to avoid name collision
+            cat_name = '@' + user_cat  # add the '@' to avoid name collision
             self.field_metadata.add_user_category(label=cat_name, name=user_cat)
 
         # add grouped search term user categories
@@ -118,7 +118,7 @@ class Cache(object):
     def field_metadata(self):
         return self.backend.field_metadata
 
-    def _get_metadata(self, book_id, get_user_categories=True): # {{{
+    def _get_metadata(self, book_id, get_user_categories=True):  # {{{
         mi = Metadata(None, template_cache=self.formatter_template_cache)
         author_ids = self._field_ids_for('authors', book_id)
         aut_list = [self._author_data(i) for i in author_ids]
@@ -403,16 +403,19 @@ class Cache(object):
         '''
         if as_file:
             ret = SpooledTemporaryFile(SPOOL_SIZE)
-            if not self.copy_cover_to(book_id, ret): return
+            if not self.copy_cover_to(book_id, ret):
+                return
             ret.seek(0)
         elif as_path:
             pt = PersistentTemporaryFile('_dbcover.jpg')
             with pt:
-                if not self.copy_cover_to(book_id, pt): return
+                if not self.copy_cover_to(book_id, pt):
+                    return
             ret = pt.name
         else:
             buf = BytesIO()
-            if not self.copy_cover_to(book_id, buf): return
+            if not self.copy_cover_to(book_id, buf):
+                return
             ret = buf.getvalue()
             if as_image:
                 from PyQt4.Qt import QImage
@@ -669,7 +672,7 @@ class Cache(object):
                 else:
                     v = sid = None
                 if name.startswith('#') and sid is None:
-                    sid = 1.0 # The value will be set to 1.0 in the db table
+                    sid = 1.0  # The value will be set to 1.0 in the db table
                 bimap[k] = v
                 if sid is not None:
                     simap[k] = sid
@@ -808,7 +811,7 @@ class Cache(object):
 
     # }}}
 
-class SortKey(object): # {{{
+class SortKey(object):  # {{{
 
     def __init__(self, fields, sort_keys, book_id):
         self.orders = tuple(1 if f[1] else -1 for f in fields)
diff --git a/src/calibre/db/categories.py b/src/calibre/db/categories.py
index f49789e16c..3f7bbb9e61 100644
--- a/src/calibre/db/categories.py
+++ b/src/calibre/db/categories.py
@@ -18,7 +18,7 @@ from calibre.utils.config_base import tweaks
 from calibre.utils.icu import sort_key
 from calibre.utils.search_query_parser import saved_searches
 
-CATEGORY_SORTS = ('name', 'popularity', 'rating') # This has to be a tuple not a set
+CATEGORY_SORTS = ('name', 'popularity', 'rating')  # This has to be a tuple not a set
 
 class Tag(object):
 
@@ -218,7 +218,7 @@ def get_categories(dbcache, sort='name', book_ids=None, icon_map=None):
                     else:
                         items.append(taglist[label][n])
                 # else: do nothing, to not include nodes w zero counts
-            cat_name = '@' + user_cat # add the '@' to avoid name collision
+            cat_name = '@' + user_cat  # add the '@' to avoid name collision
             # Not a problem if we accumulate entries in the icon map
             if icon_map is not None:
                 icon_map[cat_name] = icon_map['user:']
diff --git a/src/calibre/db/fields.py b/src/calibre/db/fields.py
index e0074de7d1..20d0d75ff4 100644
--- a/src/calibre/db/fields.py
+++ b/src/calibre/db/fields.py
@@ -31,7 +31,7 @@ class Field(object):
         self.table_type = self.table.table_type
         self._sort_key = (sort_key if dt in ('text', 'series', 'enumeration') else lambda x: x)
         self._default_sort_key = ''
-        if dt in { 'int', 'float', 'rating' }:
+        if dt in {'int', 'float', 'rating'}:
             self._default_sort_key = 0
         elif dt == 'bool':
             self._default_sort_key = None
@@ -138,7 +138,7 @@ class OneToOneField(Field):
         return self.table.book_col_map.iterkeys()
 
     def sort_keys_for_books(self, get_metadata, lang_map, all_book_ids):
-        return {id_ : self._sort_key(self.table.book_col_map.get(id_,
+        return {id_: self._sort_key(self.table.book_col_map.get(id_,
             self._default_sort_key)) for id_ in all_book_ids}
 
     def iter_searchable_values(self, get_metadata, candidates, default_value=None):
@@ -183,7 +183,7 @@ class CompositeField(OneToOneField):
         return ans
 
     def sort_keys_for_books(self, get_metadata, lang_map, all_book_ids):
-        return {id_ : sort_key(self.get_value_with_cache(id_, get_metadata)) for id_ in
+        return {id_: sort_key(self.get_value_with_cache(id_, get_metadata)) for id_ in
                 all_book_ids}
 
     def iter_searchable_values(self, get_metadata, candidates, default_value=None):
@@ -245,7 +245,7 @@ class OnDeviceField(OneToOneField):
         return iter(())
 
     def sort_keys_for_books(self, get_metadata, lang_map, all_book_ids):
-        return {id_ : self.for_book(id_) for id_ in
+        return {id_: self.for_book(id_) for id_ in
                 all_book_ids}
 
     def iter_searchable_values(self, get_metadata, candidates, default_value=None):
@@ -280,12 +280,12 @@ class ManyToOneField(Field):
         return self.table.id_map.iterkeys()
 
     def sort_keys_for_books(self, get_metadata, lang_map, all_book_ids):
-        ans = {id_ : self.table.book_col_map.get(id_, None)
+        ans = {id_: self.table.book_col_map.get(id_, None)
                 for id_ in all_book_ids}
-        sk_map = {cid : (self._default_sort_key if cid is None else
+        sk_map = {cid: (self._default_sort_key if cid is None else
                 self._sort_key(self.table.id_map[cid]))
                 for cid in ans.itervalues()}
-        return {id_ : sk_map[cid] for id_, cid in ans.iteritems()}
+        return {id_: sk_map[cid] for id_, cid in ans.iteritems()}
 
     def iter_searchable_values(self, get_metadata, candidates, default_value=None):
         cbm = self.table.col_book_map
@@ -327,14 +327,14 @@ class ManyToManyField(Field):
         return self.table.id_map.iterkeys()
 
     def sort_keys_for_books(self, get_metadata, lang_map, all_book_ids):
-        ans = {id_ : self.table.book_col_map.get(id_, ())
+        ans = {id_: self.table.book_col_map.get(id_, ())
                 for id_ in all_book_ids}
         all_cids = set()
         for cids in ans.itervalues():
             all_cids = all_cids.union(set(cids))
-        sk_map = {cid : self._sort_key(self.table.id_map[cid])
+        sk_map = {cid: self._sort_key(self.table.id_map[cid])
                 for cid in all_cids}
-        return {id_ : (tuple(sk_map[cid] for cid in cids) if cids else
+        return {id_: (tuple(sk_map[cid] for cid in cids) if cids else
                         (self._default_sort_key,))
                 for id_, cids in ans.iteritems()}
 
@@ -369,9 +369,9 @@ class IdentifiersField(ManyToManyField):
 
     def sort_keys_for_books(self, get_metadata, lang_map, all_book_ids):
         'Sort by identifier keys'
-        ans = {id_ : self.table.book_col_map.get(id_, ())
+        ans = {id_: self.table.book_col_map.get(id_, ())
                 for id_ in all_book_ids}
-        return {id_ : (tuple(sorted(cids.iterkeys())) if cids else
+        return {id_: (tuple(sorted(cids.iterkeys())) if cids else
                         (self._default_sort_key,))
                 for id_, cids in ans.iteritems()}
 
@@ -397,9 +397,9 @@ class AuthorsField(ManyToManyField):
 
     def author_data(self, author_id):
         return {
-            'name' : self.table.id_map[author_id],
-            'sort' : self.table.asort_map[author_id],
-            'link' : self.table.alink_map[author_id],
+            'name': self.table.id_map[author_id],
+            'sort': self.table.asort_map[author_id],
+            'link': self.table.alink_map[author_id],
         }
 
     def category_sort_value(self, item_id, book_ids, lang_map):
@@ -505,9 +505,9 @@ class TagsField(ManyToManyField):
 
 def create_field(name, table):
     cls = {
-            ONE_ONE : OneToOneField,
-            MANY_ONE : ManyToOneField,
-            MANY_MANY : ManyToManyField,
+            ONE_ONE: OneToOneField,
+            MANY_ONE: ManyToOneField,
+            MANY_MANY: ManyToManyField,
         }[table.table_type]
     if name == 'authors':
         cls = AuthorsField
diff --git a/src/calibre/db/locking.py b/src/calibre/db/locking.py
index d08c7b99fe..0791a5ac07 100644
--- a/src/calibre/db/locking.py
+++ b/src/calibre/db/locking.py
@@ -39,7 +39,7 @@ def create_locks():
     l = SHLock()
     return RWLockWrapper(l), RWLockWrapper(l, is_shared=False)
 
-class SHLock(object): # {{{
+class SHLock(object):  # {{{
     '''
     Shareable lock class. Used to implement the Multiple readers-single writer
     paradigm. As best as I can tell, neither writer nor reader starvation
@@ -191,7 +191,7 @@ class SHLock(object): # {{{
         try:
             return self._free_waiters.pop()
         except IndexError:
-            return Condition(self._lock)#, verbose=True)
+            return Condition(self._lock)
 
     def _return_waiter(self, waiter):
         self._free_waiters.append(waiter)
diff --git a/src/calibre/db/schema_upgrades.py b/src/calibre/db/schema_upgrades.py
index f3ca6f9852..c8eaa748c7 100644
--- a/src/calibre/db/schema_upgrades.py
+++ b/src/calibre/db/schema_upgrades.py
@@ -172,7 +172,6 @@ class SchemaUpgrade(object):
         '''
         )
 
-
     def upgrade_version_6(self):
         'Show authors in order'
         self.conn.execute('''
@@ -337,7 +336,7 @@ class SchemaUpgrade(object):
                 FROM {tn};
 
                 '''.format(tn=table_name, cn=column_name,
-                           vcn=view_column_name, scn= sort_column_name))
+                           vcn=view_column_name, scn=sort_column_name))
             self.conn.execute(script)
 
         def create_cust_tag_browser_view(table_name, link_table_name):
diff --git a/src/calibre/db/search.py b/src/calibre/db/search.py
index 57039e191d..c7fed18f9d 100644
--- a/src/calibre/db/search.py
+++ b/src/calibre/db/search.py
@@ -64,7 +64,7 @@ def _match(query, value, matchkind, use_primary_find_in_search=True):
     else:
         internal_match_ok = False
     for t in value:
-        try:     ### ignore regexp exceptions, required because search-ahead tries before typing is finished
+        try:  # ignore regexp exceptions, required because search-ahead tries before typing is finished
             t = icu_lower(t)
             if (matchkind == EQUALS_MATCH):
                 if internal_match_ok:
@@ -95,20 +95,20 @@ def _match(query, value, matchkind, use_primary_find_in_search=True):
     return False
 # }}}
 
-class DateSearch(object): # {{{
+class DateSearch(object):  # {{{
 
     def __init__(self):
         self.operators = {
-            '='   : (1, self.eq),
-            '!='  : (2, self.ne),
-            '>'   : (1, self.gt),
-            '>='  : (2, self.ge),
-            '<'   : (1, self.lt),
-            '<='  : (2, self.le),
+            '=': (1, self.eq),
+            '!=': (2, self.ne),
+            '>': (1, self.gt),
+            '>=': (2, self.ge),
+            '<': (1, self.lt),
+            '<=': (2, self.le),
         }
-        self.local_today         = { '_today', 'today', icu_lower(_('today')) }
-        self.local_yesterday     = { '_yesterday', 'yesterday', icu_lower(_('yesterday')) }
-        self.local_thismonth     = { '_thismonth', 'thismonth', icu_lower(_('thismonth')) }
+        self.local_today         = {'_today', 'today', icu_lower(_('today'))}
+        self.local_yesterday     = {'_yesterday', 'yesterday', icu_lower(_('yesterday'))}
+        self.local_thismonth     = {'_thismonth', 'thismonth', icu_lower(_('thismonth'))}
         self.daysago_pat = re.compile(r'(%s|daysago|_daysago)$'%_('daysago'))
 
     def eq(self, dbdate, query, field_count):
@@ -216,16 +216,16 @@ class DateSearch(object): # {{{
         return matches
 # }}}
 
-class NumericSearch(object): # {{{
+class NumericSearch(object):  # {{{
 
     def __init__(self):
         self.operators = {
-            '=':( 1, lambda r, q: r == q ),
-            '>':( 1, lambda r, q: r is not None and r > q ),
-            '<':( 1, lambda r, q: r is not None and r < q ),
-            '!=':( 2, lambda r, q: r != q ),
-            '>=':( 2, lambda r, q: r is not None and r >= q ),
-            '<=':( 2, lambda r, q: r is not None and r <= q )
+            '=':(1, lambda r, q: r == q),
+            '>':(1, lambda r, q: r is not None and r > q),
+            '<':(1, lambda r, q: r is not None and r < q),
+            '!=':(2, lambda r, q: r != q),
+            '>=':(2, lambda r, q: r is not None and r >= q),
+            '<=':(2, lambda r, q: r is not None and r <= q)
         }
 
     def __call__(self, query, field_iter, location, datatype, candidates, is_many=False):
@@ -267,7 +267,7 @@ class NumericSearch(object): # {{{
                 p, relop = self.operators['=']
 
             cast = int
-            if  dt == 'rating':
+            if dt == 'rating':
                 cast = lambda x: 0 if x is None else int(x)
                 adjust = lambda x: x/2
             elif dt in ('float', 'composite'):
@@ -303,7 +303,7 @@ class NumericSearch(object): # {{{
 
 # }}}
 
-class BooleanSearch(object): # {{{
+class BooleanSearch(object):  # {{{
 
     def __init__(self):
         self.local_no        = icu_lower(_('no'))
@@ -324,27 +324,27 @@ class BooleanSearch(object): # {{{
         for val, book_ids in field_iter():
             val = force_to_bool(val)
             if not bools_are_tristate:
-                if val is None or not val: # item is None or set to false
-                    if query in { self.local_no, self.local_unchecked, 'no', '_no', 'false' }:
+                if val is None or not val:  # item is None or set to false
+                    if query in {self.local_no, self.local_unchecked, 'no', '_no', 'false'}:
                         matches |= book_ids
-                else: # item is explicitly set to true
-                    if query in { self.local_yes, self.local_checked, 'yes', '_yes', 'true' }:
+                else:  # item is explicitly set to true
+                    if query in {self.local_yes, self.local_checked, 'yes', '_yes', 'true'}:
                         matches |= book_ids
             else:
                 if val is None:
-                    if query in { self.local_empty, self.local_blank, 'empty', '_empty', 'false' }:
+                    if query in {self.local_empty, self.local_blank, 'empty', '_empty', 'false'}:
                         matches |= book_ids
-                elif not val: # is not None and false
-                    if query in { self.local_no, self.local_unchecked, 'no', '_no', 'true' }:
+                elif not val:  # is not None and false
+                    if query in {self.local_no, self.local_unchecked, 'no', '_no', 'true'}:
                         matches |= book_ids
-                else: # item is not None and true
-                    if query in { self.local_yes, self.local_checked, 'yes', '_yes', 'true' }:
+                else:  # item is not None and true
+                    if query in {self.local_yes, self.local_checked, 'yes', '_yes', 'true'}:
                         matches |= book_ids
         return matches
 
 # }}}
 
-class KeyPairSearch(object): # {{{
+class KeyPairSearch(object):  # {{{
 
     def __call__(self, query, field_iter, candidates, use_primary_find):
         matches = set()
@@ -547,11 +547,12 @@ class Parser(SearchQueryParser):
         field_metadata = {}
 
         for x, fm in self.field_metadata.iteritems():
-            if x.startswith('@'): continue
+            if x.startswith('@'):
+                continue
             if fm['search_terms'] and x != 'series_sort':
                 all_locs.add(x)
                 field_metadata[x] = fm
-                if fm['datatype'] in { 'composite', 'text', 'comments', 'series', 'enumeration' }:
+                if fm['datatype'] in {'composite', 'text', 'comments', 'series', 'enumeration'}:
                     text_fields.add(x)
 
         locations = all_locs if location == 'all' else {location}
@@ -687,8 +688,8 @@ class Search(object):
             dbcache, all_book_ids, dbcache.pref('grouped_search_terms'),
             self.date_search, self.num_search, self.bool_search,
             self.keypair_search,
-            prefs[ 'limit_search_columns' ],
-            prefs[ 'limit_search_columns_to' ], self.all_search_locations,
+            prefs['limit_search_columns'],
+            prefs['limit_search_columns_to'], self.all_search_locations,
             virtual_fields)
 
         try:
diff --git a/src/calibre/db/tables.py b/src/calibre/db/tables.py
index bbc5e3bdef..fc62fbe951 100644
--- a/src/calibre/db/tables.py
+++ b/src/calibre/db/tables.py
@@ -82,7 +82,7 @@ class OneToOneTable(Table):
             self.metadata['column'], self.metadata['table'])):
             self.book_col_map[row[0]] = self.unserialize(row[1])
 
-class  PathTable(OneToOneTable):
+class PathTable(OneToOneTable):
 
     def set_path(self, book_id, path, db):
         self.book_col_map[book_id] = path
diff --git a/src/calibre/db/view.py b/src/calibre/db/view.py
index e0f99eede0..633fc6d9f9 100644
--- a/src/calibre/db/view.py
+++ b/src/calibre/db/view.py
@@ -60,10 +60,10 @@ class View(object):
             else:
                 try:
                     self._field_getters[idx] = {
-                        'id'      : self._get_id,
-                        'au_map'  : self.get_author_data,
+                        'id': self._get_id,
+                        'au_map': self.get_author_data,
                         'ondevice': self.get_ondevice,
-                        'marked'  : self.get_marked,
+                        'marked': self.get_marked,
                     }[col]
                 except KeyError:
                     self._field_getters[idx] = partial(self.get, col)
diff --git a/src/calibre/db/write.py b/src/calibre/db/write.py
index 29a27e16bf..87e7179661 100644
--- a/src/calibre/db/write.py
+++ b/src/calibre/db/write.py
@@ -417,7 +417,7 @@ def many_many(book_id_val_map, db, field, allow_case_change, *args):
 
 # }}}
 
-def identifiers(book_id_val_map, db, field, *args): # {{{
+def identifiers(book_id_val_map, db, field, *args):  # {{{
     table = field.table
     updates = set()
     for book_id, identifiers in book_id_val_map.iteritems():