diff --git a/python_basics/set_frozenset/README.md b/python_basics/set_frozenset/README.md
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@@ -10,7 +10,54 @@
 
 Questions to [David Rotermund](mailto:davrot@uni-bremen.de)
 
+{: .topic-optional}
+This is an optional topic!
+
+# [Set Types — set, frozenset](https://docs.python.org/3/library/stdtypes.html#set-types-set-frozenset)
+
+> A set object is an unordered collection of distinct hashable objects. Common uses include membership testing, removing duplicates from a sequence, and computing mathematical operations such as intersection, union, difference, and symmetric difference.
+> 
+> Like other collections, sets support x in set, len(set), and for x in set. Being an unordered collection, sets do not record element position or order of insertion. **Accordingly, sets do not support indexing, slicing, or other sequence-like behavior.**
+> 
+> There are currently two built-in set types, set and frozenset. 
+> * The **set type is mutable** — the contents can be changed using methods like add() and remove(). Since it is mutable, it has no hash value and cannot be used as either a dictionary key or as an element of another set.
+> * The **frozenset type is immutable and hashable** — its contents cannot be altered after it is created; it can therefore be used as a dictionary key or as an element of another set.
+
 
 ```python
+class set([iterable])
+class frozenset([iterable])
 ```
 
+> Return a new set or frozenset object whose elements are taken from iterable. The elements of a set must be hashable. To represent sets of sets, the inner sets must be frozenset objects. If iterable is not specified, a new empty set is returned.
+> 
+> Sets can be created by several means:
+> * Use a comma-separated list of elements within braces: {'jack', 'sjoerd'}
+> * Use a set comprehension: {c for c in 'abracadabra' if c not in 'abc'}
+> * Use the type constructor: set(), set('foobar'), set(['a', 'b', 'foo'])
+
+
+```python
+
+```
+
+The following table lists operations **available for set** that do not apply to immutable instances of frozenset:
+
+|||
+|---|---|
+| update(*others)| Update the set, adding elements from all others. |
+| set \|= other \| ... | Update the set, adding elements from all others.|
+| intersection_update(*others) | Update the set, keeping only elements found in it and all others.|
+| set &= other & ... | Update the set, keeping only elements found in it and all others.|
+|difference_update(*others)| Update the set, removing elements found in others. |
+|set -= other \| ...| Update the set, removing elements found in others.|
+|symmetric_difference_update(other)|Update the set, keeping only elements found in either set, but not in both.|
+|set ^= other|Update the set, keeping only elements found in either set, but not in both.|
+|add(elem)|Add element elem to the set.|
+|remove(elem)|Remove element elem from the set. Raises KeyError if elem is not contained in the set.|
+|discard(elem)|Remove element elem from the set if it is present.|
+|pop()|Remove and return an arbitrary element from the set. Raises KeyError if the set is empty.|
+|clear() | Remove all elements from the set.|
+
+
+