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Correct design.rst dictionaries section #11272

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viagluck Dec 21, 2018
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9 changes: 5 additions & 4 deletions Doc/faq/design.rst
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Expand Up @@ -490,7 +490,8 @@ times don't require an actual resize.
How are dictionaries implemented in CPython?
--------------------------------------------

CPython's dictionaries are implemented as resizable hash tables. Compared to
CPython's dictionaries are implemented as resizable
`hash tables <https://en.wikipedia.org/wiki/Hash_table>`_. Compared to
B-trees, this gives better performance for lookup (the most common operation by
far) under most circumstances, and the implementation is simpler.

Expand All @@ -499,9 +500,9 @@ using the :func:`hash` built-in function. The hash code varies widely depending
on the key and a per-process seed; for example, "Python" could hash to
-539294296 while "python", a string that differs by a single bit, could hash
to 1142331976. The hash code is then used to calculate a location in an
internal array where the value will be stored. Assuming that you're storing
keys that all have different hash values, this means that dictionaries take
constant time -- O(1), in Big-O notation -- to retrieve a key.
internal array where the value will be stored. In the average-case a dictionary
will take constant time -- O(1), in Big-O notation -- to retrieve a key, whereas
in the worst-case it will take linear time, or O(n).


Why must dictionary keys be immutable?
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