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python/s/filter-unique.md

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+---
+title: Filter unique list values
+type: snippet
+language: python
+tags: [list]
+cover: feathers
+dateModified: 2020-11-02T19:27:53+02:00
+---
+
+Creates a list with the unique values filtered out.
+
+- Use `collections.Counter` to get the count of each value in the list.
+- Use a list comprehension to create a list containing only the non-unique values.
+
+```py
+from collections import Counter
+
+def filter_unique(lst):
+  return [item for item, count in Counter(lst).items() if count > 1]
+```
+
+```py
+filter_unique([1, 2, 2, 3, 4, 4, 5]) # [2, 4]
+```