+Here the presence or absence of other attributes including `style` is irrelevant for the data we need, and so the regex must not depend on it
+
+
+#### Keep the regular expressions as simple as possible, but no simpler
+
+Since many extractors deal with unstructured data provided by websites, we will often need to use very complex regular expressions. You should try to use the *simplest* regex that can accomplish what you want. In other words, each part of the regex must have a reason for existing. If you can take out a symbol and the functionality does not change, the symbol should not be there.
+
+##### Example
+
+Correct:
+
+```python
+_VALID_URL = r'https?://(?:www\.)?website\.com/(?:[^/]+/){3,4}(?P<display_id>[^/]+)_(?P<id>\d+)'
+```
+
+Incorrect:
+
+```python
+_VALID_URL = r'https?:\/\/(?:www\.)?website\.com\/[^\/]+/[^\/]+/[^\/]+(?:\/[^\/]+)?\/(?P<display_id>[^\/]+)_(?P<id>\d+)'
+```
+
+#### Do not misuse `.` and use the correct quantifiers (`+*?`)
+
+Avoid creating regexes that over-match because of wrong use of quantifiers. Also try to avoid non-greedy matching (`?`) where possible since they could easily result in [catastrophic backtracking](https://www.regular-expressions.info/catastrophic.html)
+
+Correct:
+
+```python
+title = self._search_regex(r'<span\b[^>]+class="title"[^>]*>([^<]+)', webpage, 'title')
+```
+
+Incorrect:
+
+```python
+title = self._search_regex(r'<span\b.*class="title".*>(.+?)<', webpage, 'title')
+```