diff --git a/youtube_dl/YoutubeDL.py b/youtube_dl/YoutubeDL.py
old mode 100755
new mode 100644
index 4c762bf2c..b52b6b6ca
--- a/youtube_dl/YoutubeDL.py
+++ b/youtube_dl/YoutubeDL.py
@@ -540,7 +540,9 @@ class YoutubeDL(object):
         """Print message to stdout if not in quiet mode."""
         return self.to_stdout(message, skip_eol, check_quiet=True)
 
-    def _write_string(self, s, out=None, only_once=False, _cache=set()):
+    def _write_string(self, s, out=None, only_once=False, _cache=None):
+        if _cache is None:
+            _cache = set()
         if only_once and s in _cache:
             return
         write_string(s, out=out, encoding=self.params.get('encoding'))
@@ -838,7 +840,7 @@ class YoutubeDL(object):
         for key, value in extra_info.items():
             info_dict.setdefault(key, value)
 
-    def extract_info(self, url, download=True, ie_key=None, extra_info={},
+    def extract_info(self, url, download=True, ie_key=None, extra_info=None,
                      process=True, force_generic_extractor=False):
         """
         Return a list with a dictionary for each video extracted.
@@ -854,6 +856,8 @@ class YoutubeDL(object):
             must be True for download to work.
         force_generic_extractor -- force using the generic extractor
         """
+        if extra_info is None:
+            extra_info = {}
 
         if not ie_key and force_generic_extractor:
             ie_key = 'Generic'
@@ -998,7 +1002,7 @@ class YoutubeDL(object):
             'extractor_key': ie.ie_key(),
         })
 
-    def process_ie_result(self, ie_result, download=True, extra_info={}):
+    def process_ie_result(self, ie_result, download=True, extra_info=None):
         """
         Take the result of the ie (may be modified) and resolve all unresolved
         references (URLs, playlist items).
@@ -1006,6 +1010,8 @@ class YoutubeDL(object):
         It will also download the videos if 'download'.
         Returns the resolved ie_result.
         """
+        if extra_info is None:
+            extra_info = {}
         result_type = ie_result.get('_type', 'video')
 
         if result_type in ('url', 'url_transparent'):
diff --git a/youtube_dl/compat.py b/youtube_dl/compat.py
index a985cb03e..7f1a2ffb0 100644
--- a/youtube_dl/compat.py
+++ b/youtube_dl/compat.py
@@ -3740,8 +3740,10 @@ else:
                 except Exception:
                     pass
 
-        def __repr__(self, _repr_running={}):
+        def __repr__(self, _repr_running=None):
             # skip recursive items ...
+            if _repr_running is None:
+                _repr_running = {}
             call_key = id(self), _get_ident()
             if _repr_running.get(call_key):
                 return '...'
diff --git a/youtube_dl/downloader/__init__.py b/youtube_dl/downloader/__init__.py
index d701d6292..a48d45790 100644
--- a/youtube_dl/downloader/__init__.py
+++ b/youtube_dl/downloader/__init__.py
@@ -5,7 +5,9 @@ from ..utils import (
 )
 
 
-def get_suitable_downloader(info_dict, params={}):
+def get_suitable_downloader(info_dict, params=None):
+    if params is None:
+        params = {}
     info_dict['protocol'] = determine_protocol(info_dict)
     info_copy = info_dict.copy()
     return _get_suitable_downloader(info_copy, params)
@@ -39,8 +41,10 @@ PROTOCOL_MAP = {
 }
 
 
-def _get_suitable_downloader(info_dict, params={}):
+def _get_suitable_downloader(info_dict, params=None):
     """Get the downloader class that can handle the info dict."""
+    if params is None:
+        params = {}
 
     # if (info_dict.get('start_time') or info_dict.get('end_time')) and not info_dict.get('requested_formats') and FFmpegFD.can_download(info_dict):
     #     return FFmpegFD
diff --git a/youtube_dl/downloader/external.py b/youtube_dl/downloader/external.py
index 4fbc0f520..5154fe0d3 100644
--- a/youtube_dl/downloader/external.py
+++ b/youtube_dl/downloader/external.py
@@ -111,7 +111,9 @@ class ExternalFD(FileDownloader):
     def _valueless_option(self, command_option, param, expected_value=True):
         return cli_valueless_option(self.params, command_option, param, expected_value)
 
-    def _configuration_args(self, default=[]):
+    def _configuration_args(self, default=None):
+        if default is None:
+            default = []
         return cli_configuration_args(self.params, 'external_downloader_args', default)
 
     def _write_cookies(self):
diff --git a/youtube_dl/extractor/adobepass.py b/youtube_dl/extractor/adobepass.py
index 38dca1b0a..65cf0b408 100644
--- a/youtube_dl/extractor/adobepass.py
+++ b/youtube_dl/extractor/adobepass.py
@@ -1360,7 +1360,9 @@ class AdobePassIE(InfoExtractor):
             token_expires = unified_timestamp(re.sub(r'[_ ]GMT', '', xml_text(token, date_ele)))
             return token_expires and token_expires <= int(time.time())
 
-        def post_form(form_page_res, note, data={}):
+        def post_form(form_page_res, note, data=None):
+            if data is None:
+                data = {}
             form_page, urlh = form_page_res
             post_url = self._html_search_regex(r'<form[^>]+action=(["\'])(?P<url>.+?)\1', form_page, 'post url', group='url')
             if not re.match(r'https?://', post_url):
diff --git a/youtube_dl/extractor/brightcove.py b/youtube_dl/extractor/brightcove.py
index 6022076ac..8c87bb9d7 100644
--- a/youtube_dl/extractor/brightcove.py
+++ b/youtube_dl/extractor/brightcove.py
@@ -468,7 +468,9 @@ class BrightcoveNewIE(AdobePassIE):
 
         return entries
 
-    def _parse_brightcove_metadata(self, json_data, video_id, headers={}):
+    def _parse_brightcove_metadata(self, json_data, video_id, headers=None):
+        if headers is None:
+            headers = {}
         title = json_data['name'].strip()
 
         num_drm_sources = 0
diff --git a/youtube_dl/extractor/common.py b/youtube_dl/extractor/common.py
index a0901dab5..d5dd04de6 100644
--- a/youtube_dl/extractor/common.py
+++ b/youtube_dl/extractor/common.py
@@ -644,12 +644,16 @@ class InfoExtractor(object):
         else:
             assert False
 
-    def _request_webpage(self, url_or_request, video_id, note=None, errnote=None, fatal=True, data=None, headers={}, query={}, expected_status=None):
+    def _request_webpage(self, url_or_request, video_id, note=None, errnote=None, fatal=True, data=None, headers=None, query=None, expected_status=None):
         """
         Return the response handle.
 
         See _download_webpage docstring for arguments specification.
         """
+        if headers is None:
+            headers = {}
+        if query is None:
+            query = {}
         if note is None:
             self.report_download_webpage(video_id)
         elif note is not False:
@@ -702,12 +706,16 @@ class InfoExtractor(object):
                 self.report_warning(errmsg)
                 return False
 
-    def _download_webpage_handle(self, url_or_request, video_id, note=None, errnote=None, fatal=True, encoding=None, data=None, headers={}, query={}, expected_status=None):
+    def _download_webpage_handle(self, url_or_request, video_id, note=None, errnote=None, fatal=True, encoding=None, data=None, headers=None, query=None, expected_status=None):
         """
         Return a tuple (page content as string, URL handle).
 
         See _download_webpage docstring for arguments specification.
         """
+        if headers is None:
+            headers = {}
+        if query is None:
+            query = {}
         # Strip hashes from the URL (#1038)
         if isinstance(url_or_request, (compat_str, str)):
             url_or_request = url_or_request.partition('#')[0]
@@ -804,7 +812,7 @@ class InfoExtractor(object):
     def _download_webpage(
             self, url_or_request, video_id, note=None, errnote=None,
             fatal=True, tries=1, timeout=5, encoding=None, data=None,
-            headers={}, query={}, expected_status=None):
+            headers=None, query=None, expected_status=None):
         """
         Return the data of the page as a string.
 
@@ -838,6 +846,10 @@ class InfoExtractor(object):
             Note that this argument does not affect success status codes (2xx)
             which are always accepted.
         """
+        if headers is None:
+            headers = {}
+        if query is None:
+            query = {}
 
         success = False
         try_count = 0
@@ -862,13 +874,17 @@ class InfoExtractor(object):
     def _download_xml_handle(
             self, url_or_request, video_id, note='Downloading XML',
             errnote='Unable to download XML', transform_source=None,
-            fatal=True, encoding=None, data=None, headers={}, query={},
+            fatal=True, encoding=None, data=None, headers=None, query=None,
             expected_status=None):
         """
         Return a tuple (xml as an compat_etree_Element, URL handle).
 
         See _download_webpage docstring for arguments specification.
         """
+        if headers is None:
+            headers = {}
+        if query is None:
+            query = {}
         res = self._download_webpage_handle(
             url_or_request, video_id, note, errnote, fatal=fatal,
             encoding=encoding, data=data, headers=headers, query=query,
@@ -884,12 +900,16 @@ class InfoExtractor(object):
             self, url_or_request, video_id,
             note='Downloading XML', errnote='Unable to download XML',
             transform_source=None, fatal=True, encoding=None,
-            data=None, headers={}, query={}, expected_status=None):
+            data=None, headers=None, query=None, expected_status=None):
         """
         Return the xml as an compat_etree_Element.
 
         See _download_webpage docstring for arguments specification.
         """
+        if headers is None:
+            headers = {}
+        if query is None:
+            query = {}
         res = self._download_xml_handle(
             url_or_request, video_id, note=note, errnote=errnote,
             transform_source=transform_source, fatal=fatal, encoding=encoding,
@@ -912,13 +932,17 @@ class InfoExtractor(object):
     def _download_json_handle(
             self, url_or_request, video_id, note='Downloading JSON metadata',
             errnote='Unable to download JSON metadata', transform_source=None,
-            fatal=True, encoding=None, data=None, headers={}, query={},
+            fatal=True, encoding=None, data=None, headers=None, query=None,
             expected_status=None):
         """
         Return a tuple (JSON object, URL handle).
 
         See _download_webpage docstring for arguments specification.
         """
+        if headers is None:
+            headers = {}
+        if query is None:
+            query = {}
         res = self._download_webpage_handle(
             url_or_request, video_id, note, errnote, fatal=fatal,
             encoding=encoding, data=data, headers=headers, query=query,
@@ -933,13 +957,17 @@ class InfoExtractor(object):
     def _download_json(
             self, url_or_request, video_id, note='Downloading JSON metadata',
             errnote='Unable to download JSON metadata', transform_source=None,
-            fatal=True, encoding=None, data=None, headers={}, query={},
+            fatal=True, encoding=None, data=None, headers=None, query=None,
             expected_status=None):
         """
         Return the JSON object as a dict.
 
         See _download_webpage docstring for arguments specification.
         """
+        if headers is None:
+            headers = {}
+        if query is None:
+            query = {}
         res = self._download_json_handle(
             url_or_request, video_id, note=note, errnote=errnote,
             transform_source=transform_source, fatal=fatal, encoding=encoding,
@@ -1640,7 +1668,9 @@ class InfoExtractor(object):
                 unique_formats.append(f)
         formats[:] = unique_formats
 
-    def _is_valid_url(self, url, video_id, item='video', headers={}):
+    def _is_valid_url(self, url, video_id, item='video', headers=None):
+        if headers is None:
+            headers = {}
         url = self._proto_relative_url(url, scheme='http:')
         # For now assume non HTTP(S) URLs always valid
         if not (url.startswith('http://') or url.startswith('https://')):
@@ -1680,7 +1710,11 @@ class InfoExtractor(object):
 
     def _extract_f4m_formats(self, manifest_url, video_id, preference=None, f4m_id=None,
                              transform_source=lambda s: fix_xml_ampersands(s).strip(),
-                             fatal=True, m3u8_id=None, data=None, headers={}, query={}):
+                             fatal=True, m3u8_id=None, data=None, headers=None, query=None):
+        if headers is None:
+            headers = {}
+        if query is None:
+            query = {}
         manifest = self._download_xml(
             manifest_url, video_id, 'Downloading f4m manifest',
             'Unable to download f4m manifest',
@@ -1817,8 +1851,12 @@ class InfoExtractor(object):
     def _extract_m3u8_formats(self, m3u8_url, video_id, ext=None,
                               entry_protocol='m3u8', preference=None,
                               m3u8_id=None, note=None, errnote=None,
-                              fatal=True, live=False, data=None, headers={},
-                              query={}):
+                              fatal=True, live=False, data=None, headers=None,
+                              query=None):
+        if headers is None:
+            headers = {}
+        if query is None:
+            query = {}
         res = self._download_webpage_handle(
             m3u8_url, video_id,
             note=note or 'Downloading m3u8 information',
@@ -2673,7 +2711,11 @@ class InfoExtractor(object):
                         subtitles.setdefault(lang or 'und', []).append(f)
         return formats, subtitles
 
-    def _extract_ism_formats(self, ism_url, video_id, ism_id=None, note=None, errnote=None, fatal=True, data=None, headers={}, query={}):
+    def _extract_ism_formats(self, ism_url, video_id, ism_id=None, note=None, errnote=None, fatal=True, data=None, headers=None, query=None):
+        if headers is None:
+            headers = {}
+        if query is None:
+            query = {}
         res = self._download_xml_handle(
             ism_url, video_id,
             note=note or 'Downloading ISM manifest',
@@ -2908,7 +2950,9 @@ class InfoExtractor(object):
                 entries.append(media_info)
         return entries
 
-    def _extract_akamai_formats(self, manifest_url, video_id, hosts={}):
+    def _extract_akamai_formats(self, manifest_url, video_id, hosts=None):
+        if hosts is None:
+            hosts = {}
         signed = 'hdnea=' in manifest_url
         if not signed:
             # https://learn.akamai.com/en-us/webhelp/media-services-on-demand/stream-packaging-user-guide/GUID-BE6C0F73-1E06-483B-B0EA-57984B91B7F9.html
@@ -2964,7 +3008,9 @@ class InfoExtractor(object):
 
         return formats
 
-    def _extract_wowza_formats(self, url, video_id, m3u8_entry_protocol='m3u8_native', skip_protocols=[]):
+    def _extract_wowza_formats(self, url, video_id, m3u8_entry_protocol='m3u8_native', skip_protocols=None):
+        if skip_protocols is None:
+            skip_protocols = []
         query = compat_urlparse.urlparse(url).query
         url = re.sub(r'/(?:manifest|playlist|jwplayer)\.(?:m3u8|f4m|mpd|smil)', '', url)
         mobj = re.search(
@@ -3204,7 +3250,9 @@ class InfoExtractor(object):
         return res
 
     def _set_cookie(self, domain, name, value, expire_time=None, port=None,
-                    path='/', secure=False, discard=False, rest={}, **kwargs):
+                    path='/', secure=False, discard=False, rest=None, **kwargs):
+        if rest is None:
+            rest = {}
         cookie = compat_cookiejar_Cookie(
             0, name, value, port, port is not None, domain, True,
             domain.startswith('.'), path, True, secure, expire_time,
diff --git a/youtube_dl/extractor/naver.py b/youtube_dl/extractor/naver.py
index 61fc59126..b720d57ef 100644
--- a/youtube_dl/extractor/naver.py
+++ b/youtube_dl/extractor/naver.py
@@ -29,7 +29,9 @@ class NaverBaseIE(InfoExtractor):
         formats = []
         get_list = lambda x: try_get(video_data, lambda y: y[x + 's']['list'], list) or []
 
-        def extract_formats(streams, stream_type, query={}):
+        def extract_formats(streams, stream_type, query=None):
+            if query is None:
+                query = {}
             for stream in streams:
                 stream_url = stream.get('source')
                 if not stream_url:
diff --git a/youtube_dl/extractor/nexx.py b/youtube_dl/extractor/nexx.py
index 586c1b7eb..4f08fb339 100644
--- a/youtube_dl/extractor/nexx.py
+++ b/youtube_dl/extractor/nexx.py
@@ -146,7 +146,9 @@ class NexxIE(InfoExtractor):
             '%s said: %s' % (self.IE_NAME, response['metadata']['errorhint']),
             expected=True)
 
-    def _call_api(self, domain_id, path, video_id, data=None, headers={}):
+    def _call_api(self, domain_id, path, video_id, data=None, headers=None):
+        if headers is None:
+            headers = {}
         headers['Content-Type'] = 'application/x-www-form-urlencoded; charset=UTF-8'
         result = self._download_json(
             'https://api.nexx.cloud/v3/%s/%s' % (domain_id, path), video_id,
diff --git a/youtube_dl/extractor/nuevo.py b/youtube_dl/extractor/nuevo.py
index be1e09d37..3d34ae6f2 100644
--- a/youtube_dl/extractor/nuevo.py
+++ b/youtube_dl/extractor/nuevo.py
@@ -10,7 +10,9 @@ from ..utils import (
 
 
 class NuevoBaseIE(InfoExtractor):
-    def _extract_nuevo(self, config_url, video_id, headers={}):
+    def _extract_nuevo(self, config_url, video_id, headers=None):
+        if headers is None:
+            headers = {}
         config = self._download_xml(
             config_url, video_id, transform_source=lambda s: s.strip(),
             headers=headers)
diff --git a/youtube_dl/extractor/openload.py b/youtube_dl/extractor/openload.py
index 45b1add73..5685b62cb 100644
--- a/youtube_dl/extractor/openload.py
+++ b/youtube_dl/extractor/openload.py
@@ -162,7 +162,7 @@ class PhantomJSwrapper(object):
                 cookie['expire_time'] = cookie['expiry']
             self.extractor._set_cookie(**compat_kwargs(cookie))
 
-    def get(self, url, html=None, video_id=None, note=None, note2='Executing JS on webpage', headers={}, jscode='saveAndExit();'):
+    def get(self, url, html=None, video_id=None, note=None, note2='Executing JS on webpage', headers=None, jscode='saveAndExit();'):
         """
         Downloads webpage (if needed) and executes JS
 
@@ -198,6 +198,8 @@ class PhantomJSwrapper(object):
             });
             check();
         """
+        if headers is None:
+            headers = {}
         if 'saveAndExit();' not in jscode:
             raise ExtractorError('`saveAndExit();` not found in `jscode`')
         if not html:
diff --git a/youtube_dl/extractor/theplatform.py b/youtube_dl/extractor/theplatform.py
index adfe11e31..be76db8f9 100644
--- a/youtube_dl/extractor/theplatform.py
+++ b/youtube_dl/extractor/theplatform.py
@@ -343,7 +343,9 @@ class ThePlatformFeedIE(ThePlatformBaseIE):
         'only_matching': True,
     }]
 
-    def _extract_feed_info(self, provider_id, feed_id, filter_query, video_id, custom_fields=None, asset_types_query={}, account_id=None):
+    def _extract_feed_info(self, provider_id, feed_id, filter_query, video_id, custom_fields=None, asset_types_query=None, account_id=None):
+        if asset_types_query is None:
+            asset_types_query = {}
         real_url = self._URL_TEMPLATE % (self.http_scheme(), provider_id, feed_id, filter_query)
         entry = self._download_json(real_url, video_id)['entries'][0]
         main_smil_url = 'http://link.theplatform.com/s/%s/media/guid/%d/%s' % (provider_id, account_id, entry['guid']) if account_id else entry.get('plmedia$publicUrl')
diff --git a/youtube_dl/extractor/turner.py b/youtube_dl/extractor/turner.py
index 81229a54b..8d1c4dcc4 100644
--- a/youtube_dl/extractor/turner.py
+++ b/youtube_dl/extractor/turner.py
@@ -50,7 +50,11 @@ class TurnerBaseIE(AdobePassIE):
             self._AKAMAI_SPE_TOKEN_CACHE[secure_path] = token
         return video_url + '?hdnea=' + token
 
-    def _extract_cvp_info(self, data_src, video_id, path_data={}, ap_data={}, fatal=False):
+    def _extract_cvp_info(self, data_src, video_id, path_data=None, ap_data=None, fatal=False):
+        if path_data is None:
+            path_data = {}
+        if ap_data is None:
+            ap_data = {}
         video_data = self._download_xml(
             data_src, video_id,
             transform_source=lambda s: fix_xml_ampersands(s).strip(),
diff --git a/youtube_dl/extractor/tvnow.py b/youtube_dl/extractor/tvnow.py
index 9c8a8a0dc..41a048fa4 100644
--- a/youtube_dl/extractor/tvnow.py
+++ b/youtube_dl/extractor/tvnow.py
@@ -205,7 +205,9 @@ class TVNowNewIE(InfoExtractor):
 
 
 class TVNowNewBaseIE(InfoExtractor):
-    def _call_api(self, path, video_id, query={}):
+    def _call_api(self, path, video_id, query=None):
+        if query is None:
+            query = {}
         result = self._download_json(
             'https://apigw.tvnow.de/module/' + path, video_id, query=query)
         error = result.get('error')
diff --git a/youtube_dl/extractor/twitter.py b/youtube_dl/extractor/twitter.py
index cfa7a7326..a696f9d81 100644
--- a/youtube_dl/extractor/twitter.py
+++ b/youtube_dl/extractor/twitter.py
@@ -79,7 +79,9 @@ class TwitterBaseIE(InfoExtractor):
                 'height': int(m.group('height')),
             })
 
-    def _call_api(self, path, video_id, query={}):
+    def _call_api(self, path, video_id, query=None):
+        if query is None:
+            query = {}
         headers = {
             'Authorization': 'Bearer AAAAAAAAAAAAAAAAAAAAAPYXBAAAAAAACLXUNDekMxqa8h%2F40K4moUkGsoc%3DTYfbDKbT3jJPCEVnMYqilB28NHfOPqkca3qaAxGfsyKCs0wRbw',
         }
diff --git a/youtube_dl/extractor/youtube.py b/youtube_dl/extractor/youtube.py
index 81a019143..22a02e2cb 100644
--- a/youtube_dl/extractor/youtube.py
+++ b/youtube_dl/extractor/youtube.py
@@ -484,7 +484,9 @@ class YoutubeBaseInfoExtractor(InfoExtractor):
                    T(compat_str)))
 
     #  @functools.cached_property
-    def is_authenticated(self, _cache={}):
+    def is_authenticated(self, _cache=None):
+        if _cache is None:
+            _cache = {}
         if self not in _cache:
             _cache[self] = bool(self._generate_sapisidhash_header())
         return _cache[self]
@@ -633,7 +635,13 @@ class YoutubeBaseInfoExtractor(InfoExtractor):
             ('owner', 'videoOwner'), 'videoOwnerRenderer', 'title',
             'runs', Ellipsis]
 
-    def _extract_channel_id(self, webpage, videodetails={}, metadata={}, renderers=[]):
+    def _extract_channel_id(self, webpage, videodetails=None, metadata=None, renderers=None):
+        if videodetails is None:
+            videodetails = {}
+        if metadata is None:
+            metadata = {}
+        if renderers is None:
+            renderers = []
         channel_id = None
         if any((videodetails, metadata, renderers)):
             channel_id = (
@@ -648,7 +656,13 @@ class YoutubeBaseInfoExtractor(InfoExtractor):
             'channelId', webpage, 'channel id', default=None)
 
     def _extract_author_var(self, webpage, var_name,
-                            videodetails={}, metadata={}, renderers=[]):
+                            videodetails=None, metadata=None, renderers=None):
+        if videodetails is None:
+            videodetails = {}
+        if metadata is None:
+            metadata = {}
+        if renderers is None:
+            renderers = []
         result = None
         paths = {
             #       (HTML, videodetails, metadata, renderers)
@@ -1774,7 +1788,9 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
             raise ExtractorError(
                 'Cannot identify player %r' % (player_url,), cause=e)
 
-    def _player_js_cache_key(self, player_url, extra_id=None, _cache={}):
+    def _player_js_cache_key(self, player_url, extra_id=None, _cache=None):
+        if _cache is None:
+            _cache = {}
         if player_url not in _cache:
             player_id = self._extract_player_info(player_url)
             player_path = remove_start(
diff --git a/youtube_dl/jsinterp.py b/youtube_dl/jsinterp.py
index 7630e2099..f63e65f0b 100644
--- a/youtube_dl/jsinterp.py
+++ b/youtube_dl/jsinterp.py
@@ -700,7 +700,9 @@ class JSInterpreter(object):
         return separated[0][1:].strip(), separated[1].strip()
 
     @staticmethod
-    def _all_operators(_cached=[]):
+    def _all_operators(_cached=None):
+        if _cached is None:
+            _cached = []
         if not _cached:
             _cached.extend(itertools.chain(
                 # Ref: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence
diff --git a/youtube_dl/options.py b/youtube_dl/options.py
index 9b0d77a23..d48003de8 100644
--- a/youtube_dl/options.py
+++ b/youtube_dl/options.py
@@ -40,7 +40,9 @@ def _hide_login_info(opts):
 
 
 def parseOpts(overrideArguments=None):
-    def _readOptions(filename_bytes, default=[]):
+    def _readOptions(filename_bytes, default=None):
+        if default is None:
+            default = []
         try:
             optionf = open(filename_bytes, encoding=preferredencoding())
         except IOError:
diff --git a/youtube_dl/postprocessor/common.py b/youtube_dl/postprocessor/common.py
index 599dd1df2..7ece806ff 100644
--- a/youtube_dl/postprocessor/common.py
+++ b/youtube_dl/postprocessor/common.py
@@ -61,7 +61,9 @@ class PostProcessor(object):
         except Exception:
             self._downloader.report_warning(errnote)
 
-    def _configuration_args(self, default=[]):
+    def _configuration_args(self, default=None):
+        if default is None:
+            default = []
         return cli_configuration_args(self._downloader.params, 'postprocessor_args', default)
 
 
diff --git a/youtube_dl/utils.py b/youtube_dl/utils.py
index 02a49ff49..a83dcb2bd 100644
--- a/youtube_dl/utils.py
+++ b/youtube_dl/utils.py
@@ -4006,9 +4006,11 @@ prepend_extension = functools.partial(_change_extension, True)
 replace_extension = functools.partial(_change_extension, False)
 
 
-def check_executable(exe, args=[]):
+def check_executable(exe, args=None):
     """ Checks if the given binary is installed somewhere in PATH, and returns its name.
     args can be a list of arguments for a short output (like -version) """
+    if args is None:
+        args = []
     try:
         process_communicate_or_kill(subprocess.Popen(
             [exe] + args, stdout=subprocess.PIPE, stderr=subprocess.PIPE))
@@ -4017,10 +4019,12 @@ def check_executable(exe, args=[]):
     return exe
 
 
-def get_exe_version(exe, args=['--version'],
+def get_exe_version(exe, args=None,
                     version_re=None, unrecognized='present'):
     """ Returns the version of the specified executable,
     or False if the executable is not present """
+    if args is None:
+        args = []
     try:
         # STDIN should be redirected too. On UNIX-like systems, ffmpeg triggers
         # SIGTTOU if youtube-dl is run in the background.
@@ -4322,7 +4326,11 @@ def update_url_query(url, query):
     return update_url(url, query_update=query)
 
 
-def update_Request(req, url=None, data=None, headers={}, query={}):
+def update_Request(req, url=None, data=None, headers=None, query=None):
+    if headers is None:
+        headers = {}
+    if query is None:
+        query = {}
     req_headers = req.headers.copy()
     req_headers.update(headers)
     req_data = data if data is not None else req.data
@@ -5153,7 +5161,9 @@ def cli_valueless_option(params, command_option, param, expected_value=True):
     return [command_option] if param == expected_value else []
 
 
-def cli_configuration_args(params, param, default=[]):
+def cli_configuration_args(params, param, default=None):
+    if default is None:
+        default = []
     ex_args = params.get(param)
     if ex_args is None:
         return default