+Long lines policy
+
+There is a soft limit to keep lines of code under 80 characters long.
+This means it should be respected if possible and if it does not make
+readability and code maintenance worse.
+
+For example, you should NEVER split long string literals like URLs or
+some other often copied entities over multiple lines to fit this limit:
+
+Correct:
+
+ 'https://www.youtube.com/watch?v=FqZTN594JQw&list=PLMYEtVRpaqY00V9W81Cwmzp6N6vZqfUKD4'
+
+Incorrect:
+
+ 'https://www.youtube.com/watch?v=FqZTN594JQw&list='
+ 'PLMYEtVRpaqY00V9W81Cwmzp6N6vZqfUKD4'
+
+Inline values
+
+Extracting variables is acceptable for reducing code duplication and
+improving readability of complex expressions. However, you should avoid
+extracting variables used only once and moving them to opposite parts of
+the extractor file, which makes reading the linear flow difficult.
+
+Example
+
+Correct:
+
+ title = self._html_search_regex(r'<title>([^<]+)</title>', webpage, 'title')
+
+Incorrect:
+
+ TITLE_RE = r'<title>([^<]+)</title>'
+ # ...some lines of code...
+ title = self._html_search_regex(TITLE_RE, webpage, 'title')
+
+Collapse fallbacks
+
+Multiple fallback values can quickly become unwieldy. Collapse multiple
+fallback values into a single expression via a list of patterns.
+
+Example
+
+Good:
+
+ description = self._html_search_meta(
+ ['og:description', 'description', 'twitter:description'],
+ webpage, 'description', default=None)
+
+Unwieldy:
+
+ description = (
+ self._og_search_description(webpage, default=None)
+ or self._html_search_meta('description', webpage, default=None)
+ or self._html_search_meta('twitter:description', webpage, default=None))
+
+Methods supporting list of patterns are: _search_regex,
+_html_search_regex, _og_search_property, _html_search_meta.
+
+Trailing parentheses
+
+Always move trailing parentheses after the last argument.
+
+Example
+
+Correct:
+
+ lambda x: x['ResultSet']['Result'][0]['VideoUrlSet']['VideoUrl'],
+ list)
+
+Incorrect:
+
+ lambda x: x['ResultSet']['Result'][0]['VideoUrlSet']['VideoUrl'],
+ list,
+ )
+
+Use convenience conversion and parsing functions
+
+Wrap all extracted numeric data into safe functions from
+youtube_dl/utils.py: int_or_none, float_or_none. Use them for string to
+number conversions as well.
+
+Use url_or_none for safe URL processing.
+
+Use try_get for safe metadata extraction from parsed JSON.
+
+Use unified_strdate for uniform upload_date or any YYYYMMDD meta field
+extraction, unified_timestamp for uniform timestamp extraction,
+parse_filesize for filesize extraction, parse_count for count meta
+fields extraction, parse_resolution, parse_duration for duration
+extraction, parse_age_limit for age_limit extraction.
+
+Explore youtube_dl/utils.py for more useful convenience functions.
+
+More examples
+
+Safely extract optional description from parsed JSON
+
+ description = try_get(response, lambda x: x['result']['video'][0]['summary'], compat_str)
+
+Safely extract more optional metadata