diff --git a/src/calibre/customize/__init__.py b/src/calibre/customize/__init__.py
index 8125b3cc5f..7a0cd04b01 100644
--- a/src/calibre/customize/__init__.py
+++ b/src/calibre/customize/__init__.py
@@ -66,7 +66,7 @@ class Plugin(object):  # {{{
     #: When more than one plugin exists for a filetype,
     #: the plugins are run in order of decreasing priority.
     #: Plugins with higher priority will be run first.
-    #: The highest possible priority is ``sys.maxint``.
+    #: The highest possible priority is ``sys.maxsize``.
     #: Default priority is 1.
     priority = 1
 
diff --git a/src/calibre/devices/kobo/books.py b/src/calibre/devices/kobo/books.py
index 47082a29ed..acad03892f 100644
--- a/src/calibre/devices/kobo/books.py
+++ b/src/calibre/devices/kobo/books.py
@@ -273,10 +273,10 @@ class KTCollectionsBookList(CollectionsBookList):
                         if is_series:
                             if doing_dc:
                                 collections[cat_name][lpath] = \
-                                    (book, book.get('series_index', sys.maxint), tsval)
+                                    (book, book.get('series_index', sys.maxsize), tsval)
                             else:
                                 collections[cat_name][lpath] = \
-                                    (book, book.get(attr+'_index', sys.maxint), tsval)
+                                    (book, book.get(attr+'_index', sys.maxsize), tsval)
                         else:
                             collections[cat_name][lpath] = (book, tsval, tsval)
                         if show_debug:
diff --git a/src/calibre/devices/paladin/driver.py b/src/calibre/devices/paladin/driver.py
index e7d90b4294..49c2699c2e 100644
--- a/src/calibre/devices/paladin/driver.py
+++ b/src/calibre/devices/paladin/driver.py
@@ -350,7 +350,7 @@ class PALADIN(USBMS):
                 values (?,?,?,?,?,?,?,?)
                 '''
                 t = (title, author, book.get('comments', None), int(time.time() * 1000),
-                        book.get('series', None), book.get('series_index', sys.maxint), lpath,
+                        book.get('series', None), book.get('series_index', sys.maxsize), lpath,
                         book.mime or mime_type_ext(path_to_ext(lpath)))
                 cursor.execute(query, t)
                 book.bookId = connection.last_insert_rowid()
diff --git a/src/calibre/devices/usbms/books.py b/src/calibre/devices/usbms/books.py
index 6d65e13c9c..c2ad189341 100644
--- a/src/calibre/devices/usbms/books.py
+++ b/src/calibre/devices/usbms/books.py
@@ -256,10 +256,10 @@ class CollectionsBookList(BookList):
                     elif is_series:
                         if doing_dc:
                             collections[cat_name][lpath] = \
-                                (book, book.get('series_index', sys.maxint), tsval)
+                                (book, book.get('series_index', sys.maxsize), tsval)
                         else:
                             collections[cat_name][lpath] = \
-                                (book, book.get(attr+'_index', sys.maxint), tsval)
+                                (book, book.get(attr+'_index', sys.maxsize), tsval)
                     else:
                         if lpath not in collections[cat_name]:
                             collections[cat_name][lpath] = (book, tsval, tsval)
diff --git a/src/calibre/ebooks/conversion/plugins/lrf_output.py b/src/calibre/ebooks/conversion/plugins/lrf_output.py
index d743a1de74..edae1f5688 100644
--- a/src/calibre/ebooks/conversion/plugins/lrf_output.py
+++ b/src/calibre/ebooks/conversion/plugins/lrf_output.py
@@ -55,7 +55,7 @@ class LRFOptions(object):
         self.ignore_colors = False
         from calibre.ebooks.lrf import PRS500_PROFILE
         self.profile = PRS500_PROFILE
-        self.link_levels = sys.maxint
+        self.link_levels = sys.maxsize
         self.link_exclude = '@'
         self.no_links_in_toc = True
         self.disable_chapter_detection = True
diff --git a/src/calibre/ebooks/html/input.py b/src/calibre/ebooks/html/input.py
index 6bd6183821..c5f7dcca4b 100644
--- a/src/calibre/ebooks/html/input.py
+++ b/src/calibre/ebooks/html/input.py
@@ -190,7 +190,7 @@ def depth_first(root, flat, visited=set([])):
                         visited.add(hf)
 
 
-def traverse(path_to_html_file, max_levels=sys.maxint, verbose=0, encoding=None):
+def traverse(path_to_html_file, max_levels=sys.maxsize, verbose=0, encoding=None):
     '''
     Recursively traverse all links in the HTML file.
 
diff --git a/src/calibre/ebooks/lrf/html/table.py b/src/calibre/ebooks/lrf/html/table.py
index 869febf632..43b260407e 100644
--- a/src/calibre/ebooks/lrf/html/table.py
+++ b/src/calibre/ebooks/lrf/html/table.py
@@ -154,7 +154,7 @@ class Cell(object):
                 mwidth = width
         return parindent + mwidth + 2
 
-    def text_block_size(self, tb, maxwidth=sys.maxint, debug=False):
+    def text_block_size(self, tb, maxwidth=sys.maxsize, debug=False):
         ts = tb.textStyle.attrs
         default_font = get_font(ts['fontfacename'], self.pts_to_pixels(ts['fontsize']))
         parindent = self.pts_to_pixels(ts['parindent'])
@@ -200,7 +200,7 @@ class Cell(object):
         return right+3+max(parindent, 10), bottom
 
     def text_block_preferred_width(self, tb, debug=False):
-        return self.text_block_size(tb, sys.maxint, debug=debug)[0]
+        return self.text_block_size(tb, sys.maxsize, debug=debug)[0]
 
     def preferred_width(self, debug=False):
         return ceil(max([self.text_block_preferred_width(i, debug=debug) for i in self.text_blocks]))
diff --git a/src/calibre/ebooks/metadata/opf2.py b/src/calibre/ebooks/metadata/opf2.py
index 5468c0e72d..97227867eb 100644
--- a/src/calibre/ebooks/metadata/opf2.py
+++ b/src/calibre/ebooks/metadata/opf2.py
@@ -714,7 +714,7 @@ class OPF(object):  # {{{
     def create_manifest_item(self, href, media_type, append=False):
         ids = [i.get('id', None) for i in self.itermanifest()]
         id = None
-        for c in range(1, sys.maxint):
+        for c in range(1, sys.maxsize):
             id = 'id%d'%c
             if id not in ids:
                 break
diff --git a/src/calibre/ebooks/oeb/transforms/jacket.py b/src/calibre/ebooks/oeb/transforms/jacket.py
index df658a025b..cff11f0f6f 100644
--- a/src/calibre/ebooks/oeb/transforms/jacket.py
+++ b/src/calibre/ebooks/oeb/transforms/jacket.py
@@ -143,7 +143,7 @@ class Jacket(Base):
     def remove_existing_jacket(self):
         for x in self.oeb.spine[:4]:
             if XPath(JACKET_XPATH)(x.data):
-                self.remove_images(x, limit=sys.maxint)
+                self.remove_images(x, limit=sys.maxsize)
                 self.oeb.manifest.remove(x)
                 self.log('Removed existing jacket')
                 break
diff --git a/src/calibre/ebooks/pdf/reflow.py b/src/calibre/ebooks/pdf/reflow.py
index 337147d8a7..105587e3e1 100644
--- a/src/calibre/ebooks/pdf/reflow.py
+++ b/src/calibre/ebooks/pdf/reflow.py
@@ -172,7 +172,7 @@ class Column(object):
         self.elements.sort(key=lambda x: x.bottom)
         self.top = self.elements[0].top
         self.bottom = self.elements[-1].bottom
-        self.left, self.right = sys.maxint, 0
+        self.left, self.right = sys.maxsize, 0
         for x in self:
             self.left = min(self.left, x.left)
             self.right = max(self.right, x.right)
diff --git a/src/calibre/ebooks/pdf/render/engine.py b/src/calibre/ebooks/pdf/render/engine.py
index 8cb0343df3..486873d2a7 100644
--- a/src/calibre/ebooks/pdf/render/engine.py
+++ b/src/calibre/ebooks/pdf/render/engine.py
@@ -387,7 +387,7 @@ class PdfDevice(QPaintDevice):  # {{{
         if m == self.PdmDepth:
             return 32
         if m == self.PdmNumColors:
-            return sys.maxint
+            return sys.maxsize
         if m == self.PdmWidthMM:
             return int(round(self.body_width * 0.35277777777778))
         if m == self.PdmHeightMM:
diff --git a/src/calibre/ebooks/pdf/render/gradients.py b/src/calibre/ebooks/pdf/render/gradients.py
index f4baa5ab5b..07b87f59a6 100644
--- a/src/calibre/ebooks/pdf/render/gradients.py
+++ b/src/calibre/ebooks/pdf/render/gradients.py
@@ -92,8 +92,8 @@ class LinearGradientPattern(Dictionary):
             page_rect = tuple(map(inv.map, (
                 QPointF(0, 0), QPointF(pixel_page_width, 0), QPointF(0, pixel_page_height),
                 QPointF(pixel_page_width, pixel_page_height))))
-            maxx = maxy = -sys.maxint-1
-            minx = miny = sys.maxint
+            maxx = maxy = -sys.maxsize-1
+            minx = miny = sys.maxsize
 
             for p in page_rect:
                 minx, maxx = min(minx, p.x()), max(maxx, p.x())
diff --git a/src/calibre/ebooks/rtf2xml/fields_small.py b/src/calibre/ebooks/rtf2xml/fields_small.py
index edbcb1f222..b15d4184de 100755
--- a/src/calibre/ebooks/rtf2xml/fields_small.py
+++ b/src/calibre/ebooks/rtf2xml/fields_small.py
@@ -214,7 +214,7 @@ file.
         see_string = ''
         changed_string = ''
         lines = my_string.split('\n')
-        end_bracket_count = sys.maxint
+        end_bracket_count = sys.maxsize
         for line in lines:
             token_info = line[:16]
             if token_info == 'ob<nu<open-brack':
@@ -248,7 +248,7 @@ file.
         bookmark_string = ''
         index_string = ''
         lines = my_string.split('\n')
-        end_bracket_count = sys.maxint
+        end_bracket_count = sys.maxsize
         for line in lines:
             token_info = line[:16]
             if token_info == 'ob<nu<open-brack':
@@ -335,7 +335,7 @@ file.
         book_type = 0
         toc_string = ''
         lines = my_string.split('\n')
-        end_bracket_count = sys.maxint
+        end_bracket_count = sys.maxsize
         for line in lines:
             token_info = line[:16]
             if token_info == 'ob<nu<open-brack':
diff --git a/src/calibre/gui2/lrf_renderer/text.py b/src/calibre/gui2/lrf_renderer/text.py
index aa962741d5..2f050a2e89 100644
--- a/src/calibre/gui2/lrf_renderer/text.py
+++ b/src/calibre/gui2/lrf_renderer/text.py
@@ -188,7 +188,7 @@ class TextBlock(object):
         self.font_loader, self.logger, self.opts = font_loader, logger, opts
         self.in_link = False
         self.link_activated = link_activated
-        self.max_y = self.bs.blockheight if (respect_max_y or self.bs.blockrule.lower() in ('vert-fixed', 'block-fixed')) else sys.maxint
+        self.max_y = self.bs.blockheight if (respect_max_y or self.bs.blockrule.lower() in ('vert-fixed', 'block-fixed')) else sys.maxsize
         self.height = 0
         self.peek_index = -1
 
@@ -373,7 +373,7 @@ class Line(QGraphicsItem):
             self.children = self.childItems
 
     def start_link(self, refobj, slot):
-        self.current_link = [self.current_width, sys.maxint, refobj, slot]
+        self.current_link = [self.current_width, sys.maxsize, refobj, slot]
 
     def end_link(self):
         if self.current_link is not None:
diff --git a/src/calibre/gui2/preferences/columns.py b/src/calibre/gui2/preferences/columns.py
index 3d346c41fb..8ee807c087 100644
--- a/src/calibre/gui2/preferences/columns.py
+++ b/src/calibre/gui2/preferences/columns.py
@@ -249,7 +249,7 @@ class ConfigWidget(ConfigWidgetBase, Ui_Form):
             hidden_cols.remove('ondevice')
 
         def col_pos(x):
-            return config_cols.index(x) if x in config_cols else sys.maxint
+            return config_cols.index(x) if x in config_cols else sys.maxsize
         positions = {}
         for i, col in enumerate((sorted(model.column_map, key=col_pos))):
             positions[col] = i
diff --git a/src/calibre/gui2/tweak_book/editor/smarts/html.py b/src/calibre/gui2/tweak_book/editor/smarts/html.py
index c8eb521dc2..bd27141c5f 100644
--- a/src/calibre/gui2/tweak_book/editor/smarts/html.py
+++ b/src/calibre/gui2/tweak_book/editor/smarts/html.py
@@ -58,7 +58,7 @@ def next_tag_boundary(block, offset, forward=True, max_lines=10000):
                 if not forward and boundary.offset < offset:
                     return block, boundary
         block = block.next() if forward else block.previous()
-        offset = -1 if forward else sys.maxint
+        offset = -1 if forward else sys.maxsize
         max_lines -= 1
     return None, None
 
@@ -74,11 +74,11 @@ def next_attr_boundary(block, offset, forward=True):
                 if not forward and boundary.offset <= offset:
                     return block, boundary
         block = block.next() if forward else block.previous()
-        offset = -1 if forward else sys.maxint
+        offset = -1 if forward else sys.maxsize
     return None, None
 
 
-def find_closest_containing_tag(block, offset, max_tags=sys.maxint):
+def find_closest_containing_tag(block, offset, max_tags=sys.maxsize):
     ''' Find the closest containing tag. To find it, we search for the first
     opening tag that does not have a matching closing tag before the specified
     position. Search through at most max_tags. '''
@@ -180,7 +180,7 @@ def find_end_of_attribute(block, offset):
     return block, boundary.offset
 
 
-def find_closing_tag(tag, max_tags=sys.maxint):
+def find_closing_tag(tag, max_tags=sys.maxsize):
     ''' Find the closing tag corresponding to the specified tag. To find it we
     search for the first closing tag after the specified tag that does not
     match a previous opening tag. Search through at most max_tags. '''
@@ -491,7 +491,7 @@ class Smarts(NullSmarts):
                             if boundary.is_start and not boundary.closing and boundary.offset <= offset:
                                 start_block, start_offset = block, boundary.offset
                                 break
-                    block, offset = block.previous(), sys.maxint
+                    block, offset = block.previous(), sys.maxsize
             end_block = None
             if start_block is not None:
                 end_block, boundary = next_tag_boundary(start_block, start_offset)
diff --git a/src/calibre/utils/ipc/server.py b/src/calibre/utils/ipc/server.py
index 7bc3d33b42..dab19e00f0 100644
--- a/src/calibre/utils/ipc/server.py
+++ b/src/calibre/utils/ipc/server.py
@@ -185,7 +185,7 @@ else:
 class Server(Thread):
 
     def __init__(self, notify_on_job_done=lambda x: x, pool_size=None,
-            limit=sys.maxint, enforce_cpu_limit=True):
+            limit=sys.maxsize, enforce_cpu_limit=True):
         Thread.__init__(self)
         self.daemon = True
         global _counter
diff --git a/src/calibre/utils/smtp.py b/src/calibre/utils/smtp.py
index 8da8cc7bd2..5455b9896c 100644
--- a/src/calibre/utils/smtp.py
+++ b/src/calibre/utils/smtp.py
@@ -98,7 +98,7 @@ def get_mx(host, verbose=0):
     if verbose:
         print('Find mail exchanger for', host)
     answers = list(dns.resolver.query(host, 'MX'))
-    answers.sort(key=lambda x: int(getattr(x, 'preference', sys.maxint)))
+    answers.sort(key=lambda x: int(getattr(x, 'preference', sys.maxsize)))
     return [str(x.exchange) for x in answers if hasattr(x, 'exchange')]
 
 
diff --git a/src/calibre/web/fetch/simple.py b/src/calibre/web/fetch/simple.py
index 852b00b6fa..07ac9b4a93 100644
--- a/src/calibre/web/fetch/simple.py
+++ b/src/calibre/web/fetch/simple.py
@@ -596,7 +596,7 @@ def option_parser(usage=_('%prog URL\n\nWhere URL is for example https://google.
     parser.add_option('-r', '--max-recursions', default=1,
                       help=_('Maximum number of levels to recurse i.e. depth of links to follow. Default %default'),
                       type='int', dest='max_recursions')
-    parser.add_option('-n', '--max-files', default=sys.maxint, type='int', dest='max_files',
+    parser.add_option('-n', '--max-files', default=sys.maxsize, type='int', dest='max_files',
                       help=_('The maximum number of files to download. This only applies to files from <a href> tags. Default is %default'))
     parser.add_option('--delay', default=0, dest='delay', type='float',
                       help=_('Minimum interval in seconds between consecutive fetches. Default is %default s'))