collection_protocols.ipynb

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    "# Protocols of Python Collections"
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    "**Course**: _https://app.pluralsight.com/library/courses/core-python-implementing-iterators-iterables-collections/table-of-contents_"
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    "> **Clip #01**: _https://app.pluralsight.com/course-player?clipId=a3f43cab-007c-44c4-87c5-f2e349f790a4_"
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    "Various Collections have been implemented in Python which can contain a group of diverse objects in python. Some example of collections are `list`, `dict`, `set`, `tuple`, etc. \n",
    "\n",
    "Each Protocol of Collections define a set of operations which that Collection should support in order to have that Protocol supported. For example, Iterable Protocol requires the Collection to support `__iter__()` + `__next__()` or `__getitem__()` operations."
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    "## Protocols\n",
    "Collections in Python can be organized based on the protocols they support. Following are the Protocols in Python specific to Collections:\n",
    "\n",
    "1. __Container__ Protocol:\n",
    "    - Requires the `Collection` to support __membership__ operation, with `in` and `not in` operators. \n",
    "    - Realized by the Collection by implementing `__contains__()` method.\n",
    "    - Examples: __`list, range, dict, tuple, str, bytes, set, frozenset`__\n",
    "\n",
    "\n",
    "2. __Sized__ Protocol: \n",
    "    - Requires the `Collection` to support __`len()`__ operation. \n",
    "    - Realized by the Collection by implementing `__len__()` method.\n",
    "    - Examples: __`list, range, dict, tuple, str, bytes, set, frozenset`__\n",
    "\n",
    "\n",
    "3. __Iterable__ Protocol:\n",
    "    - Requires the `Collection` to return an Iterator, when called with `iter()`.\n",
    "    - Realized by the Collection by implementing `__iter__()` method which returns an Iterator.\n",
    "    - Examples: __`list, range, dict, tuple, str, bytes, set, frozenset`__\n",
    "\n",
    "\n",
    "4. __Sequence__ Protocol:\n",
    "    - Requires the `Collection` to support following operations:\n",
    "        - Indexing: Any element of the collection can be accessed using `collection[index]` operation\n",
    "        - Element Index: The index of any element can be determined with `collection.index(elem)` operation\n",
    "        - Element Count: Number of occurrances of any element can be determined with `collection.count(elem)` operation\n",
    "        - Reverse Iterator: The collection must support `reversed()` operation\n",
    "    - Examples: __`list, range, tuple, str, bytes`__\n",
    "\n",
    "\n",
    "5. __Set__ Protocol:\n",
    "    - Requires the `Collection` to support *set algebra* operations viz. __union, intersection, difference, symmetric difference, subset, superset,__ etc.\n",
    "    - Examples: __`set, frozenset`__\n",
    "\n",
    "\n",
    "6. __Mapping__ Protocol:\n",
    "    - Requires the `Collection` to support a mapping of keys to values and ability to access a value using the key.\n",
    "    - Example: __`dict`__\n",
    "\n",
    "___NOTE__: All the above protocols support querying (reading/accessing) operations. Out of the above Protocols, the `Set`, `Sequence` and `Mapping` also support `Mutable` versions, i.e. which support in place collection modification._\n",
    "\n",
    "7. __Mutable Sequence__ Protocol: Example: __`list`__\n",
    "\n",
    "8. __Mutable Set__ Protocol: Example: __`set`__\n",
    "\n",
    "9. __Mutable Mapping__ Protocol: Example: __`dict`__"
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    "### Example Problem Statement\n",
    "To demonstrate these protocol, we will create our own `SortedFrozenSet` Collection. \n",
    "\n",
    "This collection would be a __Sized, Iterable, Sequence Container__ of a __Set__ of distinct elements _constructible_ from an _Iterable_.\n",
    "\n",
    "In this course of design, implementation and learning, we shall use the **Test Driven Development** methodology."
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    "> #### Test Driven Development (TDD)\n",
    "> TDD is a development methodology, which advocates _writing unittest cases to test the code before actually writing the code_.\n",
    ">\n",
    "> It follows the cycle of:\n",
    "\n",
    "     Red ----> Green\n",
    "      ^           /\n",
    "       \\         /\n",
    "        \\       /\n",
    "         \\     v\n",
    "         Refactor\n",
    "\n",
    "> i.e.\n",
    ">\n",
    "> 1. `Red`: Write and Run the test. The test shall (obviously) fail, as the code being tested is not written yet.\n",
    "> 2. `Green`: Write the bare minimum code and keep testing it, unless the test passes.\n",
    "> 3. `Refactor`: Reflect upon the code and improve it, if needed (for better performance or formatting, etc.)\n",
    "> 4. Move forward to writing next unittest..."
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