diff --git a/src/calibre/ebooks/metadata/sources/overdrive.py b/src/calibre/ebooks/metadata/sources/overdrive.py
index 514fb9b98e..9a3e413e67 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:
@@ -256,7 +256,7 @@ 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))
         # The search results are either from a keyword search or a multi-format list from a single ID,
diff --git a/src/calibre/ebooks/mobi/reader/mobi6.py b/src/calibre/ebooks/mobi/reader/mobi6.py
index 60e4f89aaf..94efa17bcd 100644
--- a/src/calibre/ebooks/mobi/reader/mobi6.py
+++ b/src/calibre/ebooks/mobi/reader/mobi6.py
@@ -356,13 +356,13 @@ 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):
             if x == '</body>':
@@ -699,7 +699,7 @@ 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
                                     x.xpath('descendant::text()')])