diff --git a/youtube_dl/extractor/bbc.py b/youtube_dl/extractor/bbc.py
index e62b3860e..c3176700a 100644
--- a/youtube_dl/extractor/bbc.py
+++ b/youtube_dl/extractor/bbc.py
@@ -942,7 +942,7 @@ class BBCIE(BBCCoUkIE):
 
 
 class BBCCoUkArticleIE(InfoExtractor):
-    _VALID_URL = 'http://www.bbc.co.uk/programmes/articles/(?P<id>[a-zA-Z0-9]+)'
+    _VALID_URL = r'http://www.bbc.co.uk/programmes/articles/(?P<id>[a-zA-Z0-9]+)'
     IE_NAME = 'bbc.co.uk:article'
     IE_DESC = 'BBC articles'
 
diff --git a/youtube_dl/extractor/nova.py b/youtube_dl/extractor/nova.py
index 3f9c776ef..72f72b803 100644
--- a/youtube_dl/extractor/nova.py
+++ b/youtube_dl/extractor/nova.py
@@ -12,7 +12,7 @@ from ..utils import (
 
 class NovaIE(InfoExtractor):
     IE_DESC = 'TN.cz, Prásk.tv, Nova.cz, Novaplus.cz, FANDA.tv, Krásná.cz and Doma.cz'
-    _VALID_URL = 'http://(?:[^.]+\.)?(?P<site>tv(?:noviny)?|tn|novaplus|vymena|fanda|krasna|doma|prask)\.nova\.cz/(?:[^/]+/)+(?P<id>[^/]+?)(?:\.html|/|$)'
+    _VALID_URL = r'http://(?:[^.]+\.)?(?P<site>tv(?:noviny)?|tn|novaplus|vymena|fanda|krasna|doma|prask)\.nova\.cz/(?:[^/]+/)+(?P<id>[^/]+?)(?:\.html|/|$)'
     _TESTS = [{
         'url': 'http://tvnoviny.nova.cz/clanek/novinky/co-na-sebe-sportaci-praskli-vime-jestli-pujde-hrdlicka-na-materskou.html?utm_source=tvnoviny&utm_medium=cpfooter&utm_campaign=novaplus',
         'info_dict': {
diff --git a/youtube_dl/extractor/tv2.py b/youtube_dl/extractor/tv2.py
index 1457e524e..535d0d361 100644
--- a/youtube_dl/extractor/tv2.py
+++ b/youtube_dl/extractor/tv2.py
@@ -14,7 +14,7 @@ from ..utils import (
 
 
 class TV2IE(InfoExtractor):
-    _VALID_URL = 'http://(?:www\.)?tv2\.no/v/(?P<id>\d+)'
+    _VALID_URL = r'http://(?:www\.)?tv2\.no/v/(?P<id>\d+)'
     _TEST = {
         'url': 'http://www.tv2.no/v/916509/',
         'info_dict': {
@@ -100,7 +100,7 @@ class TV2IE(InfoExtractor):
 
 
 class TV2ArticleIE(InfoExtractor):
-    _VALID_URL = 'http://(?:www\.)?tv2\.no/(?:a|\d{4}/\d{2}/\d{2}(/[^/]+)+)/(?P<id>\d+)'
+    _VALID_URL = r'http://(?:www\.)?tv2\.no/(?:a|\d{4}/\d{2}/\d{2}(/[^/]+)+)/(?P<id>\d+)'
     _TESTS = [{
         'url': 'http://www.tv2.no/2015/05/16/nyheter/alesund/krim/pingvin/6930542',
         'info_dict': {
diff --git a/youtube_dl/extractor/vgtv.py b/youtube_dl/extractor/vgtv.py
index e148b1ef5..77d8978d4 100644
--- a/youtube_dl/extractor/vgtv.py
+++ b/youtube_dl/extractor/vgtv.py
@@ -214,7 +214,7 @@ class VGTVIE(XstreamIE):
 class BTArticleIE(InfoExtractor):
     IE_NAME = 'bt:article'
     IE_DESC = 'Bergens Tidende Articles'
-    _VALID_URL = 'http://(?:www\.)?bt\.no/(?:[^/]+/)+(?P<id>[^/]+)-\d+\.html'
+    _VALID_URL = r'http://(?:www\.)?bt\.no/(?:[^/]+/)+(?P<id>[^/]+)-\d+\.html'
     _TEST = {
         'url': 'http://www.bt.no/nyheter/lokalt/Kjemper-for-internatet-1788214.html',
         'md5': '2acbe8ad129b3469d5ae51b1158878df',
@@ -241,7 +241,7 @@ class BTArticleIE(InfoExtractor):
 class BTVestlendingenIE(InfoExtractor):
     IE_NAME = 'bt:vestlendingen'
     IE_DESC = 'Bergens Tidende - Vestlendingen'
-    _VALID_URL = 'http://(?:www\.)?bt\.no/spesial/vestlendingen/#!/(?P<id>\d+)'
+    _VALID_URL = r'http://(?:www\.)?bt\.no/spesial/vestlendingen/#!/(?P<id>\d+)'
     _TESTS = [{
         'url': 'http://www.bt.no/spesial/vestlendingen/#!/86588',
         'md5': 'd7d17e3337dc80de6d3a540aefbe441b',
diff --git a/youtube_dl/extractor/wdr.py b/youtube_dl/extractor/wdr.py
index a851578e0..65cab4069 100644
--- a/youtube_dl/extractor/wdr.py
+++ b/youtube_dl/extractor/wdr.py
@@ -244,7 +244,7 @@ class WDRMobileIE(InfoExtractor):
 
 
 class WDRMausIE(InfoExtractor):
-    _VALID_URL = 'http://(?:www\.)?wdrmaus\.de/(?:[^/]+/){,2}(?P<id>[^/?#]+)(?:/index\.php5|(?<!index)\.php5|/(?:$|[?#]))'
+    _VALID_URL = r'http://(?:www\.)?wdrmaus\.de/(?:[^/]+/){,2}(?P<id>[^/?#]+)(?:/index\.php5|(?<!index)\.php5|/(?:$|[?#]))'
     IE_DESC = 'Sendung mit der Maus'
     _TESTS = [{
         'url': 'http://www.wdrmaus.de/aktuelle-sendung/index.php5',