diff --git a/src/calibre/ebooks/metadata/sources/overdrive.py b/src/calibre/ebooks/metadata/sources/overdrive.py
index 514fb9b98e..18aa6b03bd 100644
--- a/src/calibre/ebooks/metadata/sources/overdrive.py
+++ b/src/calibre/ebooks/metadata/sources/overdrive.py
@@ -150,7 +150,7 @@ class OverDrive(Source):
         fix_slashes = re.compile(r'\\/')
         thumbimage = fix_slashes.sub('/', thumbimage)
         worldcatlink = fix_slashes.sub('/', worldcatlink)
-        cover_url = re.sub('(?P<img>(Ima?g(eType-)?))200', '\\g<img>100', thumbimage)
+        cover_url = re.sub(r'(?P<img>(Ima?g(eType-)?))200', r'\g<img>100', thumbimage)
         social_metadata_url = base_url+'TitleInfo.aspx?ReserveID='+reserveid+'&FormatID='+formatid
         series_num = ''
         if not series:
@@ -235,7 +235,7 @@ class OverDrive(Source):
             xreq.add_header('Referer', q_init_search)
             xreq.add_header('Accept', 'application/json, text/javascript, */*')
             raw = br.open_novisit(xreq).read()
-            for m in re.finditer(type(u'')(r'"iTotalDisplayRecords":(?P<displayrecords>\d+).*?"iTotalRecords":(?P<totalrecords>\d+)'), raw):
+            for m in re.finditer(type('')(r'"iTotalDisplayRecords":(?P<displayrecords>\d+).*?"iTotalRecords":(?P<totalrecords>\d+)'), raw):
                 if int(m.group('totalrecords')) == 0:
                     return ''
                 elif int(m.group('displayrecords')) >= 1:
@@ -256,9 +256,9 @@ class OverDrive(Source):
 
     def sort_ovrdrv_results(self, raw, log, title=None, title_tokens=None, author=None, author_tokens=None, ovrdrv_id=None):
         close_matches = []
-        raw = re.sub('.*?\\[\\[(?P<content>.*?)\\]\\].*', '[[\\g<content>]]', raw)
+        raw = re.sub(r'.*?\[\[(?P<content>.*?)\]\].*', r'[[\g<content>]]', raw)
         results = json.loads(raw)
-        # log.error('raw results are:'+str(results))
+        # log.error('raw results are:'+type('')(results))
         # The search results are either from a keyword search or a multi-format list from a single ID,
         # sort through the results for closest match/format
         if results:
@@ -336,7 +336,7 @@ class OverDrive(Source):
         req.add_header('Referer', search_url)
         req.add_header('Accept', 'application/json, text/javascript, */*')
         raw = br.open_novisit(req)
-        raw = str(list(raw))
+        raw = type('')(list(raw))
         clean_cj = mechanize.CookieJar()
         br.set_cookiejar(clean_cj)
         return self.sort_ovrdrv_results(raw, log, None, None, None, ovrdrv_id)
@@ -443,7 +443,7 @@ class OverDrive(Source):
                 mi.language = lang
 
         if ebook_isbn:
-            # print "ebook isbn is "+str(ebook_isbn[0])
+            # print("ebook isbn is "+type('')(ebook_isbn[0]))
             isbn = check_isbn(ebook_isbn[0].strip())
             if isbn:
                 self.cache_isbn_to_identifier(isbn, ovrdrv_id)
diff --git a/src/calibre/ebooks/mobi/__init__.py b/src/calibre/ebooks/mobi/__init__.py
index add994ba37..bea6a1736c 100644
--- a/src/calibre/ebooks/mobi/__init__.py
+++ b/src/calibre/ebooks/mobi/__init__.py
@@ -1,5 +1,6 @@
 #!/usr/bin/env  python2
 # vim:fileencoding=UTF-8:ts=4:sw=4:sta:et:sts=4:ai
+from __future__ import absolute_import, division, print_function, unicode_literals
 
 __license__   = 'GPL v3'
 __copyright__ = '2008, Kovid Goyal <kovid at kovidgoyal.net>'
diff --git a/src/calibre/ebooks/mobi/debug/containers.py b/src/calibre/ebooks/mobi/debug/containers.py
index a14194db0b..bfd3d2cc42 100644
--- a/src/calibre/ebooks/mobi/debug/containers.py
+++ b/src/calibre/ebooks/mobi/debug/containers.py
@@ -8,7 +8,7 @@ __copyright__ = '2014, Kovid Goyal <kovid at kovidgoyal.net>'
 from struct import unpack_from
 
 from calibre.ebooks.mobi.debug.headers import EXTHHeader
-from polyglot.builtins import filter
+from polyglot.builtins import filter, unicode_type
 
 
 class ContainerHeader(object):
@@ -63,4 +63,4 @@ class ContainerHeader(object):
         a('Null bytes after EXTH: %d' % self.null_bytes_after_exth)
         if len(self.bytes_after_exth) != self.null_bytes_after_exth:
             a('Non-null bytes present after EXTH header!!!!')
-        return '\n'.join(ans) + '\n\n' + str(self.exth) + '\n\n' + ('Title: %s' % self.title)
+        return '\n'.join(ans) + '\n\n' + unicode_type(self.exth) + '\n\n' + ('Title: %s' % self.title)
diff --git a/src/calibre/ebooks/mobi/debug/headers.py b/src/calibre/ebooks/mobi/debug/headers.py
index d263ffbb6e..b931b4b1da 100644
--- a/src/calibre/ebooks/mobi/debug/headers.py
+++ b/src/calibre/ebooks/mobi/debug/headers.py
@@ -13,7 +13,7 @@ from calibre.ebooks.mobi.reader.headers import NULL_INDEX
 from calibre.ebooks.mobi.langcodes import main_language, sub_language
 from calibre.ebooks.mobi.debug import format_bytes
 from calibre.ebooks.mobi.utils import get_trailing_data
-from polyglot.builtins import iteritems, range, as_bytes
+from polyglot.builtins import as_bytes, iteritems, range, unicode_type
 
 # PalmDB {{{
 
@@ -42,7 +42,7 @@ class PalmDOCAttributes(object):
                 self.val))
 
     def __str__(self):
-        attrs = '\n\t'.join([str(x) for x in self.attributes])
+        attrs = '\n\t'.join([unicode_type(x) for x in self.attributes])
         return 'PalmDOC Attributes: %s\n\t%s'%(bin(self.val), attrs)
 
 
@@ -84,7 +84,7 @@ class PalmDB(object):
     def __str__(self):
         ans = ['*'*20 + ' PalmDB Header '+ '*'*20]
         ans.append('Name: %r'%self.name)
-        ans.append(str(self.attributes))
+        ans.append(unicode_type(self.attributes))
         ans.append('Version: %s'%self.version)
         ans.append('Creation date: %s (%s)'%(self.creation_date.isoformat(),
             self.creation_date_raw))
@@ -255,7 +255,7 @@ class EXTHHeader(object):
         ans.append('Number of EXTH records: %d'%self.count)
         ans.append('EXTH records...')
         for r in self.records:
-            ans.append(str(r))
+            ans.append(unicode_type(r))
         return '\n'.join(ans)
 # }}}
 
@@ -496,7 +496,7 @@ class MOBIHeader(object):  # {{{
         ans = '\n'.join(ans)
 
         if self.has_exth:
-            ans += '\n\n' + str(self.exth)
+            ans += '\n\n' + unicode_type(self.exth)
             ans += '\n\nBytes after EXTH (%d bytes): %s'%(
                     len(self.bytes_after_exth),
                     format_bytes(self.bytes_after_exth))
diff --git a/src/calibre/ebooks/mobi/debug/mobi6.py b/src/calibre/ebooks/mobi/debug/mobi6.py
index 37d445399d..b57067f6f2 100644
--- a/src/calibre/ebooks/mobi/debug/mobi6.py
+++ b/src/calibre/ebooks/mobi/debug/mobi6.py
@@ -368,7 +368,7 @@ class IndexEntry(object):  # {{{
             self.index, len(self.tags))]
         for tag in self.tags:
             if tag.value is not None:
-                ans.append('\t'+str(tag))
+                ans.append('\t'+unicode_type(tag))
         if self.first_child_index != -1:
             ans.append('\tNumber of children: %d'%(self.last_child_index -
                 self.first_child_index + 1))
@@ -421,7 +421,7 @@ class IndexRecord(object):  # {{{
                 len(w), not bool(w.replace(b'\0', b''))))
         for entry in self.indices:
             offset = entry.offset
-            a(str(entry))
+            a(unicode_type(entry))
             t = self.alltext
             if offset is not None and self.alltext is not None:
                 a('\tHTML before offset: %r'%t[offset-50:offset])
@@ -608,7 +608,7 @@ class TBSIndexing(object):  # {{{
             return as_bytes('0'*(4-len(ans)) + ans)
 
         def repr_extra(x):
-            return str({bin4(k):v for k, v in iteritems(extra)})
+            return unicode_type({bin4(k):v for k, v in iteritems(extra)})
 
         tbs_type = 0
         is_periodical = self.doc_type in (257, 258, 259)
@@ -788,14 +788,14 @@ class MOBIFile(object):  # {{{
                     self.index_record.indices, self.mobi_header.type_raw)
 
     def print_header(self, f=sys.stdout):
-        print(str(self.palmdb).encode('utf-8'), file=f)
+        print(unicode_type(self.palmdb).encode('utf-8'), file=f)
         print(file=f)
         print('Record headers:', file=f)
         for i, r in enumerate(self.records):
             print('%6d. %s'%(i, r.header), file=f)
 
         print(file=f)
-        print(str(self.mobi_header).encode('utf-8'), file=f)
+        print(unicode_type(self.mobi_header).encode('utf-8'), file=f)
 # }}}
 
 
@@ -820,19 +820,19 @@ def inspect_mobi(mobi_file, ddir):
     if f.index_header is not None:
         f.index_record.alltext = alltext
         with open(os.path.join(ddir, 'index.txt'), 'wb') as out:
-            print(str(f.index_header), file=out)
+            print(unicode_type(f.index_header), file=out)
             print('\n\n', file=out)
             if f.secondary_index_header is not None:
-                print(str(f.secondary_index_header).encode('utf-8'), file=out)
+                print(unicode_type(f.secondary_index_header).encode('utf-8'), file=out)
                 print('\n\n', file=out)
             if f.secondary_index_record is not None:
-                print(str(f.secondary_index_record).encode('utf-8'), file=out)
+                print(unicode_type(f.secondary_index_record).encode('utf-8'), file=out)
                 print('\n\n', file=out)
-            print(str(f.cncx).encode('utf-8'), file=out)
+            print(unicode_type(f.cncx).encode('utf-8'), file=out)
             print('\n\n', file=out)
-            print(str(f.index_record), file=out)
+            print(unicode_type(f.index_record), file=out)
         with open(os.path.join(ddir, 'tbs_indexing.txt'), 'wb') as out:
-            print(str(f.tbs_indexing), file=out)
+            print(unicode_type(f.tbs_indexing), file=out)
         f.tbs_indexing.dump(ddir)
 
     for tdir, attr in [('text', 'text_records'), ('images', 'image_records'),
diff --git a/src/calibre/ebooks/mobi/debug/mobi8.py b/src/calibre/ebooks/mobi/debug/mobi8.py
index 3e2524584a..ad3246d1b6 100644
--- a/src/calibre/ebooks/mobi/debug/mobi8.py
+++ b/src/calibre/ebooks/mobi/debug/mobi8.py
@@ -1,7 +1,6 @@
 #!/usr/bin/env python2
 # vim:fileencoding=UTF-8:ts=4:sw=4:sta:et:sts=4:ai
 from __future__ import absolute_import, division, print_function, unicode_literals
-from polyglot.builtins import map
 
 __license__   = 'GPL v3'
 __copyright__ = '2012, Kovid Goyal <kovid@kovidgoyal.net>'
@@ -18,7 +17,7 @@ from calibre.ebooks.mobi.utils import read_font_record, decode_tbs, RECORD_SIZE
 from calibre.ebooks.mobi.debug import format_bytes
 from calibre.ebooks.mobi.reader.headers import NULL_INDEX
 from calibre.utils.imghdr import what
-from polyglot.builtins import zip, iteritems, itervalues
+from polyglot.builtins import iteritems, itervalues, map, unicode_type, zip
 
 
 class FDST(object):
@@ -95,14 +94,14 @@ class MOBIFile(object):
         self.read_tbs()
 
     def print_header(self, f=sys.stdout):
-        print(str(self.mf.palmdb).encode('utf-8'), file=f)
+        print(unicode_type(self.mf.palmdb).encode('utf-8'), file=f)
         print(file=f)
         print('Record headers:', file=f)
         for i, r in enumerate(self.mf.records):
             print('%6d. %s'%(i, r.header), file=f)
 
         print(file=f)
-        print(str(self.mf.mobi8_header).encode('utf-8'), file=f)
+        print(unicode_type(self.mf.mobi8_header).encode('utf-8'), file=f)
 
     def read_fdst(self):
         self.fdst = None
@@ -314,23 +313,23 @@ def inspect_mobi(mobi_file, ddir):
 
     for i, container in enumerate(f.containers):
         with open(os.path.join(ddir, 'container%d.txt' % (i + 1)), 'wb') as cf:
-            cf.write(str(container).encode('utf-8'))
+            cf.write(unicode_type(container).encode('utf-8'))
 
     if f.fdst:
         with open(os.path.join(ddir, 'fdst.record'), 'wb') as fo:
-            fo.write(str(f.fdst).encode('utf-8'))
+            fo.write(unicode_type(f.fdst).encode('utf-8'))
 
     with open(os.path.join(ddir, 'skel.record'), 'wb') as fo:
-        fo.write(str(f.skel_index).encode('utf-8'))
+        fo.write(unicode_type(f.skel_index).encode('utf-8'))
 
     with open(os.path.join(ddir, 'chunks.record'), 'wb') as fo:
-        fo.write(str(f.sect_index).encode('utf-8'))
+        fo.write(unicode_type(f.sect_index).encode('utf-8'))
 
     with open(os.path.join(ddir, 'ncx.record'), 'wb') as fo:
-        fo.write(str(f.ncx_index).encode('utf-8'))
+        fo.write(unicode_type(f.ncx_index).encode('utf-8'))
 
     with open(os.path.join(ddir, 'guide.record'), 'wb') as fo:
-        fo.write(str(f.guide_index).encode('utf-8'))
+        fo.write(unicode_type(f.guide_index).encode('utf-8'))
 
     with open(os.path.join(ddir, 'tbs.txt'), 'wb') as fo:
         fo.write(('\n'.join(f.indexing_data)).encode('utf-8'))
diff --git a/src/calibre/ebooks/mobi/langcodes.py b/src/calibre/ebooks/mobi/langcodes.py
index 16be630f18..be34fc1384 100644
--- a/src/calibre/ebooks/mobi/langcodes.py
+++ b/src/calibre/ebooks/mobi/langcodes.py
@@ -1,4 +1,6 @@
 #!/usr/bin/env  python2
+from __future__ import absolute_import, division, print_function, unicode_literals
+
 __license__   = 'GPL v3'
 __copyright__ = '2008, Kovid Goyal kovid@kovidgoyal.net'
 __docformat__ = 'restructuredtext en'
diff --git a/src/calibre/ebooks/mobi/mobiml.py b/src/calibre/ebooks/mobi/mobiml.py
index 51bff9c57a..94c8114e85 100644
--- a/src/calibre/ebooks/mobi/mobiml.py
+++ b/src/calibre/ebooks/mobi/mobiml.py
@@ -1,8 +1,8 @@
+from __future__ import absolute_import, division, print_function, unicode_literals
+
 '''
 Transform XHTML/OPS-ish content into Mobipocket HTML 3.2.
 '''
-from __future__ import with_statement
-from __future__ import print_function
 
 __license__   = 'GPL v3'
 __copyright__ = '2008, Marshall T. Vandegrift <llasram@gmail.cam>'
@@ -54,7 +54,7 @@ def asfloat(value):
 def isspace(text):
     if not text:
         return True
-    if u'\xa0' in text:
+    if '\xa0' in text:
         return False
     return text.isspace()
 
@@ -139,7 +139,7 @@ class MobiMLizer(object):
             self.mobimlize_elem(body, stylizer, BlockState(nbody),
                                 [FormatState()])
             item.data = nroot
-            # print etree.tostring(nroot)
+            # print(etree.tostring(nroot))
 
     def mobimlize_font(self, ptsize):
         return self.fnums[self.fmap[ptsize]]
@@ -156,9 +156,9 @@ class MobiMLizer(object):
         text = unicode_type(text)
         if pre_wrap:
             # Replace n consecutive spaces with n-1 NBSP + space
-            text = re.sub(r' {2,}', lambda m:(u'\xa0'*(len(m.group())-1) + u' '), text)
+            text = re.sub(r' {2,}', lambda m:('\xa0'*(len(m.group())-1) + ' '), text)
         else:
-            text = text.replace(u' ', u'\xa0')
+            text = text.replace(' ', '\xa0')
 
         text = text.replace('\r\n', '\n')
         text = text.replace('\r', '\n')
@@ -201,7 +201,7 @@ class MobiMLizer(object):
                 bstate.nested.append(para)
                 if tag == 'li' and len(istates) > 1:
                     istates[-2].list_num += 1
-                    para.attrib['value'] = str(istates[-2].list_num)
+                    para.attrib['value'] = unicode_type(istates[-2].list_num)
             elif tag in NESTABLE_TAGS and istate.rendered:
                 para = wrapper = bstate.nested[-1]
             elif not self.opts.mobi_ignore_margins and left > 0 and indent >= 0:
@@ -210,7 +210,7 @@ class MobiMLizer(object):
                 para = wrapper
                 emleft = int(round(left / self.profile.fbase)) - ems
                 emleft = min((emleft, 10))
-                while emleft > ems/2.0:
+                while emleft > ems / 2:
                     para = etree.SubElement(para, XHTML('blockquote'))
                     emleft -= ems
             else:
@@ -287,7 +287,7 @@ class MobiMLizer(object):
 
             if fsize != 3:
                 inline = etree.SubElement(inline, XHTML('font'),
-                                          size=str(fsize))
+                                          size=unicode_type(fsize))
             if istate.family == 'monospace':
                 inline = etree.SubElement(inline, XHTML('tt'))
             if istate.italic:
@@ -390,17 +390,17 @@ class MobiMLizer(object):
             lspace = margin + padding
             if lspace > 0:
                 spaces = int(round((lspace * 3) / style['font-size']))
-                elem.text = (u'\xa0' * spaces) + (elem.text or '')
+                elem.text = ('\xa0' * spaces) + (elem.text or '')
             margin = asfloat(style['margin-right'])
             padding = asfloat(style['padding-right'])
             rspace = margin + padding
             if rspace > 0:
                 spaces = int(round((rspace * 3) / style['font-size']))
                 if len(elem) == 0:
-                    elem.text = (elem.text or '') + (u'\xa0' * spaces)
+                    elem.text = (elem.text or '') + ('\xa0' * spaces)
                 else:
                     last = elem[-1]
-                    last.text = (last.text or '') + (u'\xa0' * spaces)
+                    last.text = (last.text or '') + ('\xa0' * spaces)
         if bstate.content and style['page-break-before'] in PAGE_BREAKS:
             bstate.pbreak = True
         istate.fsize = self.mobimlize_font(style['font-size'])
@@ -446,10 +446,10 @@ class MobiMLizer(object):
                         # See #7520 for test case
                         try:
                             pixs = int(round(float(value) /
-                                (72./self.profile.dpi)))
+                                (72/self.profile.dpi)))
                         except:
                             continue
-                        result = str(pixs)
+                        result = unicode_type(pixs)
                     istate.attrib[prop] = result
             if 'width' not in istate.attrib or 'height' not in istate.attrib:
                 href = self.current_spine_item.abshref(elem.attrib['src'])
@@ -466,22 +466,22 @@ class MobiMLizer(object):
                     else:
                         if 'width' not in istate.attrib and 'height' not in \
                                     istate.attrib:
-                            istate.attrib['width'] = str(width)
-                            istate.attrib['height'] = str(height)
+                            istate.attrib['width'] = unicode_type(width)
+                            istate.attrib['height'] = unicode_type(height)
                         else:
-                            ar = float(width)/float(height)
+                            ar = width / height
                             if 'width' not in istate.attrib:
                                 try:
                                     width = int(istate.attrib['height'])*ar
                                 except:
                                     pass
-                                istate.attrib['width'] = str(int(width))
+                                istate.attrib['width'] = unicode_type(int(width))
                             else:
                                 try:
                                     height = int(istate.attrib['width'])/ar
                                 except:
                                     pass
-                                istate.attrib['height'] = str(int(height))
+                                istate.attrib['height'] = unicode_type(int(height))
                         item.unload_data_from_memory()
         elif tag == 'hr' and asfloat(style['width']) > 0 and style._get('width') not in {'100%', 'auto'}:
             raww = style._get('width')
@@ -515,11 +515,11 @@ class MobiMLizer(object):
             t = elem.text
             if not t:
                 t = ''
-            elem.text = u'\u201c' + t
+            elem.text = '\u201c' + t
             t = elem.tail
             if not t:
                 t = ''
-            elem.tail = u'\u201d' + t
+            elem.tail = '\u201d' + t
         text = None
         if elem.text:
             if istate.preserve or istate.pre_wrap:
@@ -602,7 +602,7 @@ class MobiMLizer(object):
             bstate.pbreak = True
         if isblock:
             para = bstate.para
-            if para is not None and para.text == u'\xa0' and len(para) < 1:
+            if para is not None and para.text == '\xa0' and len(para) < 1:
                 if style.height > 2:
                     para.getparent().replace(para, etree.Element(XHTML('br')))
                 else:
diff --git a/src/calibre/ebooks/mobi/reader/headers.py b/src/calibre/ebooks/mobi/reader/headers.py
index fd82f6509d..f34b49af92 100644
--- a/src/calibre/ebooks/mobi/reader/headers.py
+++ b/src/calibre/ebooks/mobi/reader/headers.py
@@ -1,6 +1,6 @@
 #!/usr/bin/env python2
 # vim:fileencoding=UTF-8:ts=4:sw=4:sta:et:sts=4:ai
-from __future__ import (absolute_import, print_function)
+from __future__ import absolute_import, division, print_function, unicode_literals
 
 __license__   = 'GPL v3'
 __copyright__ = '2012, Kovid Goyal <kovid@kovidgoyal.net>'
@@ -294,14 +294,14 @@ class MetadataHeader(BookHeader):
     def kf8_type(self):
         if (self.mobi_version == 8 and getattr(self, 'skelidx', NULL_INDEX) !=
                 NULL_INDEX):
-            return u'standalone'
+            return 'standalone'
 
         kf8_header_index = getattr(self.exth, 'kf8_header', None)
         if kf8_header_index is None:
             return None
         try:
             if self.section_data(kf8_header_index-1) == b'BOUNDARY':
-                return u'joint'
+                return 'joint'
         except:
             pass
         return None
diff --git a/src/calibre/ebooks/mobi/reader/mobi6.py b/src/calibre/ebooks/mobi/reader/mobi6.py
index 60e4f89aaf..abc648f806 100644
--- a/src/calibre/ebooks/mobi/reader/mobi6.py
+++ b/src/calibre/ebooks/mobi/reader/mobi6.py
@@ -1,6 +1,6 @@
 #!/usr/bin/env python2
 # vim:fileencoding=UTF-8:ts=4:sw=4:sta:et:sts=4:ai
-from __future__ import (absolute_import, print_function)
+from __future__ import absolute_import, division, print_function, unicode_literals
 
 __license__   = 'GPL v3'
 __copyright__ = '2012, Kovid Goyal <kovid@kovidgoyal.net>'
@@ -169,7 +169,7 @@ class MobiReader(object):
         self.processed_html = self.processed_html.replace('</</', '</')
         self.processed_html = re.sub(r'</([a-zA-Z]+)<', r'</\1><',
                 self.processed_html)
-        self.processed_html = self.processed_html.replace(u'\ufeff', '')
+        self.processed_html = self.processed_html.replace('\ufeff', '')
         # Remove tags of the form <xyz: ...> as they can cause issues further
         # along the pipeline
         self.processed_html = re.sub(r'</{0,1}[a-zA-Z]+:\s+[^>]*>', '',
@@ -356,15 +356,15 @@ class MobiReader(object):
         # Swap inline and block level elements, and order block level elements according to priority
         # - lxml and beautifulsoup expect/assume a specific order based on xhtml spec
         self.processed_html = re.sub(
-            r'(?i)(?P<styletags>(<(h\d+|i|b|u|em|small|big|strong|tt)>\s*){1,})(?P<para><p[^>]*>)', '\\g<para>'+'\\g<styletags>', self.processed_html)
+            r'(?i)(?P<styletags>(<(h\d+|i|b|u|em|small|big|strong|tt)>\s*){1,})(?P<para><p[^>]*>)', r'\g<para>'+r'\g<styletags>', self.processed_html)
         self.processed_html = re.sub(
-            r'(?i)(?P<para></p[^>]*>)\s*(?P<styletags>(</(h\d+|i|b|u|em|small|big|strong|tt)>\s*){1,})', '\\g<styletags>'+'\\g<para>', self.processed_html)
+            r'(?i)(?P<para></p[^>]*>)\s*(?P<styletags>(</(h\d+|i|b|u|em|small|big|strong|tt)>\s*){1,})', r'\g<styletags>'+r'\g<para>', self.processed_html)
         self.processed_html = re.sub(
-            r'(?i)(?P<blockquote>(</(blockquote|div)[^>]*>\s*){1,})(?P<para></p[^>]*>)', '\\g<para>'+'\\g<blockquote>', self.processed_html)
+            r'(?i)(?P<blockquote>(</(blockquote|div)[^>]*>\s*){1,})(?P<para></p[^>]*>)', r'\g<para>'+r'\g<blockquote>', self.processed_html)
         self.processed_html = re.sub(
-            r'(?i)(?P<para><p[^>]*>)\s*(?P<blockquote>(<(blockquote|div)[^>]*>\s*){1,})', '\\g<blockquote>'+'\\g<para>', self.processed_html)
+            r'(?i)(?P<para><p[^>]*>)\s*(?P<blockquote>(<(blockquote|div)[^>]*>\s*){1,})', r'\g<blockquote>'+r'\g<para>', self.processed_html)
         bods = htmls = 0
-        for x in re.finditer(u'</body>|</html>', self.processed_html):
+        for x in re.finditer('</body>|</html>', self.processed_html):
             if x == '</body>':
                 bods +=1
             else:
@@ -442,7 +442,7 @@ class MobiReader(object):
                             # Paragraph spacer
                             # Insert nbsp so that the element is never
                             # discarded by a renderer
-                            tag.text = u'\u00a0'  # nbsp
+                            tag.text = '\u00a0'  # nbsp
                             styles.append('height: %s' %
                                     self.ensure_unit(height))
                         else:
@@ -642,11 +642,11 @@ class MobiReader(object):
             mi = MetaInformation(self.book_header.title, [_('Unknown')])
         opf = OPFCreator(os.path.dirname(htmlfile), mi)
         if hasattr(self.book_header.exth, 'cover_offset'):
-            opf.cover = u'images/%05d.jpg' % (self.book_header.exth.cover_offset + 1)
+            opf.cover = 'images/%05d.jpg' % (self.book_header.exth.cover_offset + 1)
         elif mi.cover is not None:
             opf.cover = mi.cover
         else:
-            opf.cover = u'images/%05d.jpg' % 1
+            opf.cover = 'images/%05d.jpg' % 1
             if not os.path.exists(os.path.join(os.path.dirname(htmlfile),
                 * opf.cover.split('/'))):
                 opf.cover = None
@@ -656,7 +656,7 @@ class MobiReader(object):
         if cover is not None:
             cover = cover.replace('/', os.sep)
             if os.path.exists(cover):
-                ncover = u'images'+os.sep+u'calibre_cover.jpg'
+                ncover = 'images'+os.sep+'calibre_cover.jpg'
                 if os.path.exists(ncover):
                     os.remove(ncover)
                 shutil.copyfile(cover, ncover)
@@ -664,9 +664,9 @@ class MobiReader(object):
                 opf.cover = ncover.replace(os.sep, '/')
 
         manifest = [(htmlfile, 'application/xhtml+xml'),
-            (os.path.abspath(u'styles.css'), 'text/css')]
+            (os.path.abspath('styles.css'), 'text/css')]
         bp = os.path.dirname(htmlfile)
-        added = set([])
+        added = set()
         for i in getattr(self, 'image_names', []):
             path = os.path.join(bp, 'images', i)
             added.add(path)
@@ -699,9 +699,9 @@ class MobiReader(object):
                         continue
                     if reached and x.tag == 'a':
                         href = x.get('href', '')
-                        if href and re.match('\\w+://', href) is None:
+                        if href and re.match(r'\w+://', href) is None:
                             try:
-                                text = u' '.join([t.strip() for t in
+                                text = ' '.join([t.strip() for t in
                                     x.xpath('descendant::text()')])
                             except:
                                 text = ''
diff --git a/src/calibre/ebooks/mobi/writer8/exth.py b/src/calibre/ebooks/mobi/writer8/exth.py
index 3d76721e85..d997b3ae29 100644
--- a/src/calibre/ebooks/mobi/writer8/exth.py
+++ b/src/calibre/ebooks/mobi/writer8/exth.py
@@ -107,7 +107,7 @@ def build_exth(metadata, prefer_author_sort=False, is_periodical=False,
             break
     if uuid is None:
         from uuid import uuid4
-        uuid = str(uuid4())
+        uuid = unicode_type(uuid4())
 
     if isinstance(uuid, unicode_type):
         uuid = uuid.encode('utf-8')
@@ -137,9 +137,9 @@ def build_exth(metadata, prefer_author_sort=False, is_periodical=False,
 
     # Add a publication date entry
     if metadata['date']:
-        datestr = str(metadata['date'][0])
+        datestr = unicode_type(metadata['date'][0])
     elif metadata['timestamp']:
-        datestr = str(metadata['timestamp'][0])
+        datestr = unicode_type(metadata['timestamp'][0])
 
     if datestr is None:
         raise ValueError("missing date or timestamp")
diff --git a/src/calibre/ebooks/mobi/writer8/mobi.py b/src/calibre/ebooks/mobi/writer8/mobi.py
index ac843b5ce1..da589456af 100644
--- a/src/calibre/ebooks/mobi/writer8/mobi.py
+++ b/src/calibre/ebooks/mobi/writer8/mobi.py
@@ -289,7 +289,7 @@ class KF8Book(object):
             self.extra_data_flags |= 0b10
         self.uid = random.randint(0, 0xffffffff)
 
-        self.language_code = iana2mobi(str(metadata.language[0]))
+        self.language_code = iana2mobi(unicode_type(metadata.language[0]))
         self.exth_flags = 0b1010000
         if writer.opts.mobi_periodical:
             self.exth_flags |= 0b1000
diff --git a/src/calibre/ebooks/odt/__init__.py b/src/calibre/ebooks/odt/__init__.py
index da901ade3e..8a2513c8cc 100644
--- a/src/calibre/ebooks/odt/__init__.py
+++ b/src/calibre/ebooks/odt/__init__.py
@@ -1,4 +1,6 @@
 #!/usr/bin/env  python2
+from __future__ import absolute_import, division, print_function, unicode_literals
+
 __license__   = 'GPL v3'
 __copyright__ = '2008, Kovid Goyal kovid@kovidgoyal.net'
 __docformat__ = 'restructuredtext en'
@@ -6,4 +8,3 @@ __docformat__ = 'restructuredtext en'
 '''
 Handle the Open Document Format
 '''
-
diff --git a/src/calibre/ebooks/oeb/__init__.py b/src/calibre/ebooks/oeb/__init__.py
index 4f8588535f..57af3199b4 100644
--- a/src/calibre/ebooks/oeb/__init__.py
+++ b/src/calibre/ebooks/oeb/__init__.py
@@ -1,2 +1,4 @@
+from __future__ import absolute_import, division, print_function, unicode_literals
+
 __license__   = 'GPL v3'
 __copyright__ = '2008, Marshall T. Vandegrift <llasram@gmail.com>'
diff --git a/src/calibre/ebooks/oeb/base.py b/src/calibre/ebooks/oeb/base.py
index 24560c49d7..1f87dcbe45 100644
--- a/src/calibre/ebooks/oeb/base.py
+++ b/src/calibre/ebooks/oeb/base.py
@@ -920,7 +920,7 @@ class Manifest(object):
         """
 
         def __init__(self, oeb, id, href, media_type,
-                     fallback=None, loader=str, data=None):
+                     fallback=None, loader=unicode_type, data=None):
             if href:
                 href = unicode_type(href)
             self.oeb = oeb
@@ -937,7 +937,7 @@ class Manifest(object):
             self._data = data
 
         def __repr__(self):
-            return u'Item(id=%r, href=%r, media_type=%r)' \
+            return 'Item(id=%r, href=%r, media_type=%r)' \
                 % (self.id, self.href, self.media_type)
 
         # Parsing {{{
@@ -1024,8 +1024,8 @@ class Manifest(object):
             - XML content is parsed and returned as an lxml.etree element.
             - CSS and CSS-variant content is parsed and returned as a css_parser
               CSS DOM stylesheet.
-            - All other content is returned as a :class:`str` object with no
-              special parsing.
+            - All other content is returned as a :class:`str` or :class:`bytes`
+              object with no special parsing.
             """
             data = self._data
             if data is None:
@@ -1642,7 +1642,7 @@ class TOC(object):
             po = node.play_order
             if po == 0:
                 po = 1
-            attrib = {'id': id, 'playOrder': str(po)}
+            attrib = {'id': id, 'playOrder': unicode_type(po)}
             if node.klass:
                 attrib['class'] = node.klass
             point = element(parent, NCX('navPoint'), attrib=attrib)
@@ -1925,7 +1925,7 @@ class OEBBook(object):
         for i, elem in enumerate(xpath(ncx, '//*[@playOrder and ./ncx:content[@src]]')):
             href = urlnormalize(selector(elem)[0])
             order = playorder.get(href, i)
-            elem.attrib['playOrder'] = str(order)
+            elem.attrib['playOrder'] = unicode_type(order)
         return
 
     def _to_ncx(self):
@@ -1938,12 +1938,12 @@ class OEBBook(object):
         etree.SubElement(head, NCX('meta'),
             name='dtb:uid', content=unicode_type(self.uid))
         etree.SubElement(head, NCX('meta'),
-            name='dtb:depth', content=str(self.toc.depth()))
+            name='dtb:depth', content=unicode_type(self.toc.depth()))
         generator = ''.join(['calibre (', __version__, ')'])
         etree.SubElement(head, NCX('meta'),
             name='dtb:generator', content=generator)
         etree.SubElement(head, NCX('meta'),
-            name='dtb:totalPageCount', content=str(len(self.pages)))
+            name='dtb:totalPageCount', content=unicode_type(len(self.pages)))
         maxpnum = etree.SubElement(head, NCX('meta'),
             name='dtb:maxPageNumber', content='0')
         title = etree.SubElement(ncx, NCX('docTitle'))
@@ -1954,7 +1954,7 @@ class OEBBook(object):
         if len(self.pages) > 0:
             plist = self.pages.to_ncx(ncx)
             value = max(int(x) for x in xpath(plist, '//@value'))
-            maxpnum.attrib['content'] = str(value)
+            maxpnum.attrib['content'] = unicode_type(value)
         self._update_playorder(ncx)
         return ncx
 
diff --git a/src/calibre/ebooks/oeb/normalize_css.py b/src/calibre/ebooks/oeb/normalize_css.py
index 14b1ca07f2..3b9ee27d28 100644
--- a/src/calibre/ebooks/oeb/normalize_css.py
+++ b/src/calibre/ebooks/oeb/normalize_css.py
@@ -6,13 +6,13 @@ __license__ = 'GPL v3'
 __copyright__ = '2013, Kovid Goyal <kovid at kovidgoyal.net>'
 
 import numbers
-from polyglot.builtins import iteritems, zip, string_or_bytes
 from functools import wraps
 
 from css_parser.css import PropertyValue
 from css_parser import profile as cssprofiles, CSSParser
 from tinycss.fonts3 import parse_font, serialize_font_family
 from calibre.ebooks.oeb.base import css_text
+from polyglot.builtins import iteritems, string_or_bytes, unicode_type, zip
 
 DEFAULTS = {'azimuth': 'center', 'background-attachment': 'scroll',  # {{{
             'background-color': 'transparent', 'background-image': 'none',
@@ -393,7 +393,7 @@ def test_normalization(return_tests=False):  # {{{
                 tuple('0 0 0 0'.split()) : '0',
             }):
                 for prefix in ('margin', 'padding'):
-                    css = {'%s-%s' % (prefix, x) : str(y)+'pt' if isinstance(y, numbers.Number) else y for x, y in zip(('left', 'top', 'right', 'bottom'), s)}
+                    css = {'%s-%s' % (prefix, x) : unicode_type(y)+'pt' if isinstance(y, numbers.Number) else y for x, y in zip(('left', 'top', 'right', 'bottom'), s)}
                     css = '; '.join(('%s:%s' % (k, v) for k, v in iteritems(css)))
                     style = parseStyle(css)
                     condense_rule(style)
diff --git a/src/calibre/ebooks/oeb/polish/cover.py b/src/calibre/ebooks/oeb/polish/cover.py
index a59b9b3cfe..98ae45277a 100644
--- a/src/calibre/ebooks/oeb/polish/cover.py
+++ b/src/calibre/ebooks/oeb/polish/cover.py
@@ -10,7 +10,7 @@ import shutil, re, os
 from calibre.ebooks.oeb.base import OPF, OEB_DOCS, XPath, XLINK, xml2text
 from calibre.ebooks.oeb.polish.replace import replace_links, get_recommended_folders
 from calibre.utils.imghdr import identify
-from polyglot.builtins import iteritems
+from polyglot.builtins import iteritems, unicode_type
 
 
 def set_azw3_cover(container, cover_path, report, options=None):
@@ -384,8 +384,8 @@ def create_epub_cover(container, cover_path, existing_image, options=None):
             ar = 'xMidYMid meet' if keep_aspect else 'none'
             templ = CoverManager.SVG_TEMPLATE.replace('__ar__', ar)
             templ = templ.replace('__viewbox__', '0 0 %d %d'%(width, height))
-            templ = templ.replace('__width__', str(width))
-            templ = templ.replace('__height__', str(height))
+            templ = templ.replace('__width__', unicode_type(width))
+            templ = templ.replace('__height__', unicode_type(height))
     folder = recommended_folders[tname]
     if folder:
         tname = folder + '/' + tname
diff --git a/src/calibre/ebooks/oeb/polish/parsing.py b/src/calibre/ebooks/oeb/polish/parsing.py
index 3771a1588b..1b94dce1aa 100644
--- a/src/calibre/ebooks/oeb/polish/parsing.py
+++ b/src/calibre/ebooks/oeb/polish/parsing.py
@@ -13,6 +13,7 @@ import html5_parser
 from calibre import xml_replace_entities
 from calibre.ebooks.chardet import xml_to_unicode, strip_encoding_declarations
 from calibre.utils.cleantext import clean_xml_chars
+from polyglot.builtins import unicode_type
 
 XHTML_NS     = 'http://www.w3.org/1999/xhtml'
 
@@ -83,7 +84,7 @@ def parse(raw, decoder=None, log=None, line_numbers=True, linenumber_attribute=N
         if linenumber_attribute:
             for elem in ans.iter(LxmlElement):
                 if elem.sourceline is not None:
-                    elem.set(linenumber_attribute, str(elem.sourceline))
+                    elem.set(linenumber_attribute, unicode_type(elem.sourceline))
         return ans
     except Exception:
         if log is not None:
diff --git a/src/calibre/ebooks/oeb/polish/split.py b/src/calibre/ebooks/oeb/polish/split.py
index 0acc603b71..88ddeeec04 100644
--- a/src/calibre/ebooks/oeb/polish/split.py
+++ b/src/calibre/ebooks/oeb/polish/split.py
@@ -12,7 +12,7 @@ from calibre.ebooks.oeb.base import barename, XPNSMAP, XPath, OPF, XHTML, OEB_DO
 from calibre.ebooks.oeb.polish.errors import MalformedMarkup
 from calibre.ebooks.oeb.polish.toc import node_from_loc
 from calibre.ebooks.oeb.polish.replace import LinkRebaser
-from polyglot.builtins import iteritems
+from polyglot.builtins import iteritems, unicode_type
 from polyglot.urllib import urlparse
 
 
@@ -282,7 +282,7 @@ def multisplit(container, name, xpath, before=True):
             raise AbortError('Cannot split on the <body> tag')
 
     for i, tag in enumerate(nodes):
-        tag.set('calibre-split-point', str(i))
+        tag.set('calibre-split-point', unicode_type(i))
 
     current = name
     all_names = [name]
diff --git a/src/calibre/ebooks/oeb/polish/toc.py b/src/calibre/ebooks/oeb/polish/toc.py
index c752a0735e..1e7b224070 100644
--- a/src/calibre/ebooks/oeb/polish/toc.py
+++ b/src/calibre/ebooks/oeb/polish/toc.py
@@ -9,7 +9,6 @@ __docformat__ = 'restructuredtext en'
 import re
 from collections import Counter, OrderedDict
 from functools import partial
-from polyglot.builtins import iteritems, map, unicode_type
 from operator import itemgetter
 
 from lxml import etree
@@ -24,6 +23,7 @@ from calibre.ebooks.oeb.polish.opf import set_guide_item, get_book_language
 from calibre.ebooks.oeb.polish.pretty import pretty_html_tree
 from calibre.translations.dynamic import translate
 from calibre.utils.localization import get_lang, canonicalize_lang, lang_as_iso639_1
+from polyglot.builtins import iteritems, map, unicode_type
 from polyglot.urllib import urlparse
 
 ns = etree.FunctionNamespace('calibre_xpath_extensions')
@@ -104,7 +104,7 @@ class TOC(object):
 
     def get_lines(self, lvl=0):
         frag = ('#'+self.frag) if self.frag else ''
-        ans = [(u'\t'*lvl) + u'TOC: %s --> %s%s'%(self.title, self.dest, frag)]
+        ans = [('\t'*lvl) + 'TOC: %s --> %s%s'%(self.title, self.dest, frag)]
         for child in self:
             ans.extend(child.get_lines(lvl+1))
         return ans
@@ -580,7 +580,7 @@ def create_ncx(toc, to_href, btitle, lang, uid):
     etree.SubElement(head, NCX('meta'),
         name='dtb:uid', content=unicode_type(uid))
     etree.SubElement(head, NCX('meta'),
-        name='dtb:depth', content=str(toc.depth))
+        name='dtb:depth', content=unicode_type(toc.depth))
     generator = ''.join(['calibre (', __version__, ')'])
     etree.SubElement(head, NCX('meta'),
         name='dtb:generator', content=generator)
@@ -598,7 +598,7 @@ def create_ncx(toc, to_href, btitle, lang, uid):
         for child in toc_parent:
             play_order['c'] += 1
             point = etree.SubElement(xml_parent, NCX('navPoint'), id='num_%d' % play_order['c'],
-                            playOrder=str(play_order['c']))
+                            playOrder=unicode_type(play_order['c']))
             label = etree.SubElement(point, NCX('navLabel'))
             title = child.title
             if title:
@@ -764,7 +764,7 @@ def commit_nav_toc(container, toc, lang=None, landmarks=None, previous_nav=None)
         for entry in toc.page_list:
             if container.has_name(entry['dest']) and container.mime_map[entry['dest']] in OEB_DOCS:
                 a = create_li(ol, entry)
-                a.text = str(entry['pagenum'])
+                a.text = unicode_type(entry['pagenum'])
         pretty_xml_tree(nav)
         collapse_li(nav)
     container.replace(tocname, root)
diff --git a/src/calibre/ebooks/oeb/reader.py b/src/calibre/ebooks/oeb/reader.py
index 467b0113c1..c1961ed0e2 100644
--- a/src/calibre/ebooks/oeb/reader.py
+++ b/src/calibre/ebooks/oeb/reader.py
@@ -1,8 +1,7 @@
 """
 Container-/OPF-based input OEBBook reader.
 """
-from __future__ import with_statement
-from __future__ import print_function
+from __future__ import absolute_import, division, print_function, unicode_literals
 
 __license__   = 'GPL v3'
 __copyright__ = '2008, Marshall T. Vandegrift <llasram@gmail.com>'
@@ -150,7 +149,7 @@ class OEBReader(object):
                 dict(a=__appname__, v=__version__)
         meta_info_to_oeb_metadata(mi, self.oeb.metadata, self.logger)
         m = self.oeb.metadata
-        m.add('identifier', str(uuid.uuid4()), id='uuid_id', scheme='uuid')
+        m.add('identifier', unicode_type(uuid.uuid4()), id='uuid_id', scheme='uuid')
         self.oeb.uid = self.oeb.metadata.identifier[-1]
         if not m.title:
             m.add('title', self.oeb.translate(__('Unknown')))
@@ -198,8 +197,8 @@ class OEBReader(object):
                     try:
                         data = item.data
                     except:
-                        self.oeb.log.exception(u'Failed to read from manifest '
-                                u'entry with id: %s, ignoring'%item.id)
+                        self.oeb.log.exception('Failed to read from manifest '
+                                'entry with id: %s, ignoring'%item.id)
                         invalid.add(item)
                         continue
                 if data is None:
@@ -234,7 +233,7 @@ class OEBReader(object):
                         if not scheme and href not in known:
                             new.add(href)
             unchecked.clear()
-            warned = set([])
+            warned = set()
             for href in new:
                 known.add(href)
                 is_invalid = False
@@ -276,13 +275,13 @@ class OEBReader(object):
                 media_type = media_type.lower()
             fallback = elem.get('fallback')
             if href in manifest.hrefs:
-                self.logger.warn(u'Duplicate manifest entry for %r' % href)
+                self.logger.warn('Duplicate manifest entry for %r' % href)
                 continue
             if not self.oeb.container.exists(href):
-                self.logger.warn(u'Manifest item %r not found' % href)
+                self.logger.warn('Manifest item %r not found' % href)
                 continue
             if id in manifest.ids:
-                self.logger.warn(u'Duplicate manifest id %r' % id)
+                self.logger.warn('Duplicate manifest id %r' % id)
                 id, href = manifest.generate(id, href)
             manifest.add(id, href, media_type, fallback)
         invalid = self._manifest_prune_invalid()
@@ -333,7 +332,7 @@ class OEBReader(object):
         for elem in xpath(opf, '/o2:package/o2:spine/o2:itemref'):
             idref = elem.get('idref')
             if idref not in manifest.ids:
-                self.logger.warn(u'Spine item %r not found' % idref)
+                self.logger.warn('Spine item %r not found' % idref)
                 continue
             item = manifest.ids[idref]
             if item.media_type.lower() in OEB_DOCS and hasattr(item.data, 'xpath') and not getattr(item.data, 'tag', '').endswith('}ncx'):
@@ -365,7 +364,7 @@ class OEBReader(object):
                         corrected_href = href
                         break
                 if corrected_href is None:
-                    self.logger.warn(u'Guide reference %r not found' % ref_href)
+                    self.logger.warn('Guide reference %r not found' % ref_href)
                     continue
                 ref_href = corrected_href
             typ = elem.get('type')
diff --git a/src/calibre/ebooks/oeb/stylizer.py b/src/calibre/ebooks/oeb/stylizer.py
index 9a5e8908d0..d834e26ad3 100644
--- a/src/calibre/ebooks/oeb/stylizer.py
+++ b/src/calibre/ebooks/oeb/stylizer.py
@@ -3,7 +3,7 @@
 '''
 CSS property propagation class.
 '''
-from __future__ import with_statement
+from __future__ import absolute_import, division, print_function, unicode_literals
 
 __license__   = 'GPL v3'
 __copyright__ = '2008, Marshall T. Vandegrift <llasram@gmail.com>'
@@ -32,7 +32,8 @@ _html_css_stylesheet = None
 def html_css_stylesheet():
     global _html_css_stylesheet
     if _html_css_stylesheet is None:
-        html_css = open(P('templates/html.css'), 'rb').read()
+        with open(P('templates/html.css'), 'rb') as f:
+            html_css = f.read()
         _html_css_stylesheet = parseString(html_css, validate=False)
     return _html_css_stylesheet
 
@@ -74,7 +75,7 @@ def media_ok(raw):
         return mq.negated ^ matched
 
     try:
-        for mq in CSSMedia3Parser().parse_stylesheet(u'@media %s {}' % raw).rules[0].media:
+        for mq in CSSMedia3Parser().parse_stylesheet('@media %s {}' % raw).rules[0].media:
             if query_ok(mq):
                 return True
         return False
@@ -219,14 +220,14 @@ class Stylizer(object):
                 log=logging.getLogger('calibre.css'))
         for elem in style_tags:
             if (elem.tag == XHTML('style') and elem.get('type', CSS_MIME) in OEB_STYLES and media_ok(elem.get('media'))):
-                text = elem.text if elem.text else u''
+                text = elem.text if elem.text else ''
                 for x in elem:
                     t = getattr(x, 'text', None)
                     if t:
-                        text += u'\n\n' + force_unicode(t, u'utf-8')
+                        text += '\n\n' + force_unicode(t, 'utf-8')
                     t = getattr(x, 'tail', None)
                     if t:
-                        text += u'\n\n' + force_unicode(t, u'utf-8')
+                        text += '\n\n' + force_unicode(t, 'utf-8')
                 if text:
                     text = oeb.css_preprocessor(text)
                     # We handle @import rules separately
@@ -295,7 +296,7 @@ class Stylizer(object):
         self.flatten_style = self.oeb.stylizer_rules.flatten_style
 
         self._styles = {}
-        pseudo_pat = re.compile(u':{1,2}(%s)' % ('|'.join(INAPPROPRIATE_PSEUDO_CLASSES)), re.I)
+        pseudo_pat = re.compile(':{1,2}(%s)' % ('|'.join(INAPPROPRIATE_PSEUDO_CLASSES)), re.I)
         select = Select(tree, ignore_inappropriate_pseudo_classes=True)
 
         for _, _, cssdict, text, _ in self.rules:
@@ -309,7 +310,7 @@ class Stylizer(object):
             if fl is not None:
                 fl = fl.group(1)
                 if fl == 'first-letter' and getattr(self.oeb,
-                        'plumber_output_format', '').lower() in {u'mobi', u'docx'}:
+                        'plumber_output_format', '').lower() in {'mobi', 'docx'}:
                     # Fake first-letter
                     for elem in matches:
                         for x in elem.iter('*'):
@@ -323,8 +324,8 @@ class Stylizer(object):
                                     punctuation_chars.append(text[0])
                                     text = text[1:]
 
-                                special_text = u''.join(punctuation_chars) + \
-                                        (text[0] if text else u'')
+                                special_text = ''.join(punctuation_chars) + \
+                                        (text[0] if text else '')
                                 span = x.makeelement('{%s}span' % XHTML_NS)
                                 span.text = special_text
                                 span.set('data-fake-first-letter', '1')
@@ -486,7 +487,7 @@ class Style(object):
         return unit_convert(value, base, font, self._profile.dpi, body_font_size=self._stylizer.body_font_size)
 
     def pt_to_px(self, value):
-        return (self._profile.dpi / 72.0) * value
+        return (self._profile.dpi / 72) * value
 
     @property
     def backgroundColor(self):
@@ -590,7 +591,7 @@ class Style(object):
         x = self._style.get(attr)
         if x is not None:
             if x == 'auto':
-                ans = self._unit_convert(str(img_size) + 'px', base=base)
+                ans = self._unit_convert(unicode_type(img_size) + 'px', base=base)
             else:
                 x = self._unit_convert(x, base=base)
                 if isinstance(x, numbers.Number):
@@ -602,7 +603,7 @@ class Style(object):
                 if isinstance(x, numbers.Number):
                     ans = x
         if ans is None:
-            ans = self._unit_convert(str(img_size) + 'px', base=base)
+            ans = self._unit_convert(unicode_type(img_size) + 'px', base=base)
         maa = self._style.get('max-' + attr)
         if maa is not None:
             x = self._unit_convert(maa, base=base)
diff --git a/src/calibre/ebooks/oeb/transforms/__init__.py b/src/calibre/ebooks/oeb/transforms/__init__.py
index 4a7a9ab6f5..720ff711e6 100644
--- a/src/calibre/ebooks/oeb/transforms/__init__.py
+++ b/src/calibre/ebooks/oeb/transforms/__init__.py
@@ -1,10 +1,7 @@
 #!/usr/bin/env python2
 # vim:fileencoding=UTF-8:ts=4:sw=4:sta:et:sts=4:ai
-from __future__ import with_statement
+from __future__ import absolute_import, division, print_function, unicode_literals
 
 __license__   = 'GPL v3'
 __copyright__ = '2009, Kovid Goyal <kovid@kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
-
-
-
diff --git a/src/calibre/ebooks/oeb/transforms/cover.py b/src/calibre/ebooks/oeb/transforms/cover.py
index 63b89c9b63..8fbb7bcc24 100644
--- a/src/calibre/ebooks/oeb/transforms/cover.py
+++ b/src/calibre/ebooks/oeb/transforms/cover.py
@@ -1,5 +1,6 @@
 #!/usr/bin/env python2
 # vim:fileencoding=UTF-8:ts=4:sw=4:sta:et:sts=4:ai
+from __future__ import absolute_import, division, print_function, unicode_literals
 
 __license__   = 'GPL v3'
 __copyright__ = '2010, Kovid Goyal <kovid@kovidgoyal.net>'
@@ -16,7 +17,7 @@ from polyglot.urllib import unquote
 
 class CoverManager(object):
 
-    SVG_TEMPLATE = textwrap.dedent(u'''\
+    SVG_TEMPLATE = textwrap.dedent('''\
         <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
             <head>
                 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
@@ -40,7 +41,7 @@ class CoverManager(object):
         </html>
         ''')
 
-    NONSVG_TEMPLATE = textwrap.dedent(u'''\
+    NONSVG_TEMPLATE = textwrap.dedent('''\
         <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
             <head>
                 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
@@ -103,7 +104,7 @@ class CoverManager(object):
                     pass
             img_data = create_cover(title, authors, series, series_index)
             id, href = self.oeb.manifest.generate('cover',
-                    u'cover_image.jpg')
+                    'cover_image.jpg')
             item = self.oeb.manifest.add(id, href, guess_type('t.jpg')[0],
                         data=img_data)
             m.clear('cover')
@@ -145,15 +146,15 @@ class CoverManager(object):
             self.svg_template = self.svg_template.replace('__viewbox__',
                     '0 0 %d %d'%(width, height))
             self.svg_template = self.svg_template.replace('__width__',
-                    str(width))
+                    unicode_type(width))
             self.svg_template = self.svg_template.replace('__height__',
-                    str(height))
+                    unicode_type(height))
 
             if href is not None:
                 templ = self.non_svg_template if self.no_svg_cover \
                         else self.svg_template
                 tp = templ%unquote(href)
-                id, href = m.generate('titlepage', u'titlepage.xhtml')
+                id, href = m.generate('titlepage', 'titlepage.xhtml')
                 item = m.add(id, href, guess_type('t.xhtml')[0],
                         data=etree.fromstring(tp))
         else:
diff --git a/src/calibre/ebooks/oeb/transforms/filenames.py b/src/calibre/ebooks/oeb/transforms/filenames.py
index a7959e70fc..1539663370 100644
--- a/src/calibre/ebooks/oeb/transforms/filenames.py
+++ b/src/calibre/ebooks/oeb/transforms/filenames.py
@@ -1,5 +1,6 @@
 #!/usr/bin/env python2
 # vim:fileencoding=UTF-8:ts=4:sw=4:sta:et:sts=4:ai
+from __future__ import absolute_import, division, print_function, unicode_literals
 
 __license__   = 'GPL v3'
 __copyright__ = '2010, Kovid Goyal <kovid@kovidgoyal.net>'
@@ -96,7 +97,7 @@ class UniqueFilenames(object):  # {{{
         self.opts = opts
         self.oeb = oeb
 
-        self.seen_filenames = set([])
+        self.seen_filenames = set()
         self.rename_map = {}
 
         for item in list(oeb.manifest.items):
diff --git a/src/calibre/ebooks/oeb/transforms/guide.py b/src/calibre/ebooks/oeb/transforms/guide.py
index 104a2fc1d5..e935d79cd4 100644
--- a/src/calibre/ebooks/oeb/transforms/guide.py
+++ b/src/calibre/ebooks/oeb/transforms/guide.py
@@ -1,6 +1,6 @@
 #!/usr/bin/env python2
 # vim:fileencoding=UTF-8:ts=4:sw=4:sta:et:sts=4:ai
-from __future__ import with_statement
+from __future__ import absolute_import, division, print_function, unicode_literals
 
 __license__   = 'GPL v3'
 __copyright__ = '2009, Kovid Goyal <kovid@kovidgoyal.net>'
diff --git a/src/calibre/ebooks/oeb/transforms/htmltoc.py b/src/calibre/ebooks/oeb/transforms/htmltoc.py
index a7a84dd8b3..bab65763b8 100644
--- a/src/calibre/ebooks/oeb/transforms/htmltoc.py
+++ b/src/calibre/ebooks/oeb/transforms/htmltoc.py
@@ -1,7 +1,7 @@
 '''
 HTML-TOC-adding transform.
 '''
-from __future__ import with_statement
+from __future__ import absolute_import, division, print_function, unicode_literals
 
 __license__   = 'GPL v3'
 __copyright__ = '2008, Marshall T. Vandegrift <llasram@gmail.com>'
@@ -9,6 +9,7 @@ __copyright__ = '2008, Marshall T. Vandegrift <llasram@gmail.com>'
 from calibre.ebooks.oeb.base import XML, XHTML, XHTML_NS
 from calibre.ebooks.oeb.base import XHTML_MIME, CSS_MIME
 from calibre.ebooks.oeb.base import element, XPath
+from polyglot.builtins import unicode_type
 
 __all__ = ['HTMLTOCAdder']
 
@@ -94,7 +95,7 @@ class HTMLTOCAdder(object):
             style = 'nested'
         id, css_href = oeb.manifest.generate('tocstyle', 'tocstyle.css')
         oeb.manifest.add(id, css_href, CSS_MIME, data=STYLE_CSS[style])
-        language = str(oeb.metadata.language[0])
+        language = unicode_type(oeb.metadata.language[0])
         contents = element(None, XHTML('html'), nsmap={None: XHTML_NS},
                            attrib={XML('lang'): language})
         head = element(contents, XHTML('head'))
diff --git a/src/calibre/ebooks/oeb/transforms/linearize_tables.py b/src/calibre/ebooks/oeb/transforms/linearize_tables.py
index 99d1cf8417..e86d4dd18e 100644
--- a/src/calibre/ebooks/oeb/transforms/linearize_tables.py
+++ b/src/calibre/ebooks/oeb/transforms/linearize_tables.py
@@ -1,6 +1,6 @@
 #!/usr/bin/env python2
 # vim:fileencoding=UTF-8:ts=4:sw=4:sta:et:sts=4:ai
-from __future__ import with_statement
+from __future__ import absolute_import, division, print_function, unicode_literals
 
 __license__   = 'GPL v3'
 __copyright__ = '2009, Kovid Goyal <kovid@kovidgoyal.net>'
diff --git a/src/calibre/ebooks/oeb/transforms/manglecase.py b/src/calibre/ebooks/oeb/transforms/manglecase.py
index 9269a90084..c3a198949c 100644
--- a/src/calibre/ebooks/oeb/transforms/manglecase.py
+++ b/src/calibre/ebooks/oeb/transforms/manglecase.py
@@ -1,7 +1,7 @@
 '''
 CSS case-mangling transform.
 '''
-from __future__ import with_statement
+from __future__ import absolute_import, division, print_function, unicode_literals
 
 __license__   = 'GPL v3'
 __copyright__ = '2008, Marshall T. Vandegrift <llasram@gmail.com>'
diff --git a/src/calibre/ebooks/oeb/transforms/rasterize.py b/src/calibre/ebooks/oeb/transforms/rasterize.py
index 35a96df60f..83651b23e5 100644
--- a/src/calibre/ebooks/oeb/transforms/rasterize.py
+++ b/src/calibre/ebooks/oeb/transforms/rasterize.py
@@ -1,7 +1,7 @@
 '''
 SVG rasterization transform.
 '''
-from __future__ import with_statement
+from __future__ import absolute_import, division, print_function, unicode_literals
 
 __license__   = 'GPL v3'
 __copyright__ = '2008, Marshall T. Vandegrift <llasram@gmail.com>'
@@ -77,7 +77,7 @@ class SVGRasterizer(object):
                     logger.info('Found SVG image height in %, trying to convert...')
                     try:
                         h = float(image.get('height').replace('%', ''))/100.
-                        image.set('height', str(h*sizes[1]))
+                        image.set('height', unicode_type(h*sizes[1]))
                     except:
                         logger.exception('Failed to convert percentage height:',
                                 image.get('height'))
@@ -101,7 +101,7 @@ class SVGRasterizer(object):
         buffer = QBuffer(array)
         buffer.open(QIODevice.WriteOnly)
         image.save(buffer, format)
-        return str(array)
+        return array.data()
 
     def dataize_manifest(self):
         for item in self.oeb.manifest.values():
@@ -121,10 +121,10 @@ class SVGRasterizer(object):
             if abshref not in hrefs:
                 continue
             linkee = hrefs[abshref]
-            data = str(linkee)
+            data = unicode_type(linkee)
             ext = what(None, data) or 'jpg'
             with PersistentTemporaryFile(suffix='.'+ext) as pt:
-                pt.write(data)
+                pt.write(data.encode('utf-8'))
                 self.temp_files.append(pt.name)
             elem.attrib[XLINK('href')] = pt.name
         return svg
@@ -182,7 +182,7 @@ class SVGRasterizer(object):
         height = style['height']
         width = (width / 72) * self.profile.dpi
         height = (height / 72) * self.profile.dpi
-        data = QByteArray(str(svgitem))
+        data = QByteArray(unicode_type(svgitem).encode('utf-8'))
         svg = QSvgRenderer(data)
         size = svg.defaultSize()
         size.scale(width, height, Qt.KeepAspectRatio)
@@ -202,7 +202,7 @@ class SVGRasterizer(object):
             buffer = QBuffer(array)
             buffer.open(QIODevice.WriteOnly)
             image.save(buffer, 'PNG')
-            data = str(array)
+            data = array.data()
             manifest = self.oeb.manifest
             href = os.path.splitext(svgitem.href)[0] + '.png'
             id, href = manifest.generate(svgitem.id, href)
diff --git a/src/calibre/ebooks/oeb/transforms/rescale.py b/src/calibre/ebooks/oeb/transforms/rescale.py
index f3c1c95b37..214c89509e 100644
--- a/src/calibre/ebooks/oeb/transforms/rescale.py
+++ b/src/calibre/ebooks/oeb/transforms/rescale.py
@@ -1,6 +1,6 @@
 #!/usr/bin/env python2
 # vim:fileencoding=UTF-8:ts=4:sw=4:sta:et:sts=4:ai
-from __future__ import with_statement
+from __future__ import absolute_import, division, print_function, unicode_literals
 
 __license__   = 'GPL v3'
 __copyright__ = '2009, Kovid Goyal <kovid@kovidgoyal.net>'
@@ -30,8 +30,8 @@ class RescaleImages(object):
             page_width, page_height = self.opts.dest.comic_screen_size
         else:
             page_width, page_height = self.opts.dest.width, self.opts.dest.height
-            page_width -= (self.opts.margin_left + self.opts.margin_right) * self.opts.dest.dpi/72.
-            page_height -= (self.opts.margin_top + self.opts.margin_bottom) * self.opts.dest.dpi/72.
+            page_width -= (self.opts.margin_left + self.opts.margin_right) * self.opts.dest.dpi/72
+            page_height -= (self.opts.margin_top + self.opts.margin_bottom) * self.opts.dest.dpi/72
 
         for item in self.oeb.manifest:
             if item.media_type.startswith('image'):
diff --git a/src/calibre/ebooks/oeb/writer.py b/src/calibre/ebooks/oeb/writer.py
index 5f82a05011..953c4924da 100644
--- a/src/calibre/ebooks/oeb/writer.py
+++ b/src/calibre/ebooks/oeb/writer.py
@@ -1,7 +1,7 @@
 '''
 Directory output OEBBook writer.
 '''
-from __future__ import with_statement
+from __future__ import absolute_import, division, print_function, unicode_literals
 
 __license__   = 'GPL v3'
 __copyright__ = '2008, Marshall T. Vandegrift <llasram@gmail.com>'
diff --git a/src/calibre/gui2/dialogs/plugin_updater.py b/src/calibre/gui2/dialogs/plugin_updater.py
index 275e77dadf..fe16c4a5d3 100644
--- a/src/calibre/gui2/dialogs/plugin_updater.py
+++ b/src/calibre/gui2/dialogs/plugin_updater.py
@@ -357,7 +357,7 @@ class DisplayPluginModel(QAbstractTableModel):
     def _get_display_version(self, version):
         if version is None:
             return ''
-        return '.'.join([str(v) for v in list(version)])
+        return '.'.join([unicode_type(v) for v in list(version)])
 
     def _get_status(self, display_plugin):
         if not display_plugin.is_valid_platform():
diff --git a/src/calibre/utils/speedup.c b/src/calibre/utils/speedup.c
index d270f3678c..86767d5aa0 100644
--- a/src/calibre/utils/speedup.c
+++ b/src/calibre/utils/speedup.c
@@ -139,7 +139,7 @@ speedup_fdopen(PyObject *self, PyObject *args) {
 
     if (!PyArg_ParseTuple(args, "iss|i", &fd, &name, &mode, &bufsize)) return NULL;
 #if PY_MAJOR_VERSION >= 3
-    ans = PyFile_FromFd(fd, name, mode, bufsize, NULL, NULL, NULL, 1);
+    ans = PyFile_FromFd(fd, NULL, mode, bufsize, NULL, NULL, NULL, 1);
 #else
     fp = fdopen(fd, mode);
     if (fp == NULL) return PyErr_SetFromErrno(PyExc_OSError);