diff options
Diffstat (limited to 'Doc/reference/datamodel.rst')
| -rw-r--r-- | Doc/reference/datamodel.rst | 50 |
1 files changed, 38 insertions, 12 deletions
diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst index 7dcd459..1f1a660 100644 --- a/Doc/reference/datamodel.rst +++ b/Doc/reference/datamodel.rst @@ -276,16 +276,16 @@ Sequences single: integer single: Unicode - The items of a string object are Unicode code units. A Unicode code - unit is represented by a string object of one item and can hold either - a 16-bit or 32-bit value representing a Unicode ordinal (the maximum - value for the ordinal is given in ``sys.maxunicode``, and depends on - how Python is configured at compile time). Surrogate pairs may be - present in the Unicode object, and will be reported as two separate - items. The built-in functions :func:`chr` and :func:`ord` convert - between code units and nonnegative integers representing the Unicode - ordinals as defined in the Unicode Standard 3.0. Conversion from and to - other encodings are possible through the string method :meth:`encode`. + A string is a sequence of values that represent Unicode codepoints. + All the codepoints in range ``U+0000 - U+10FFFF`` can be represented + in a string. Python doesn't have a :c:type:`chr` type, and + every character in the string is represented as a string object + with length ``1``. The built-in function :func:`ord` converts a + character to its codepoint (as an integer); :func:`chr` converts + an integer in range ``0 - 10FFFF`` to the corresponding character. + :meth:`str.encode` can be used to convert a :class:`str` to + :class:`bytes` using the given encoding, and :meth:`bytes.decode` can + be used to achieve the opposite. Tuples .. index:: @@ -448,6 +448,11 @@ Callable types +-------------------------+-------------------------------+-----------+ | :attr:`__name__` | The function's name | Writable | +-------------------------+-------------------------------+-----------+ + | :attr:`__qualname__` | The function's | Writable | + | | :term:`qualified name` | | + | | | | + | | .. versionadded:: 3.3 | | + +-------------------------+-------------------------------+-----------+ | :attr:`__module__` | The name of the module the | Writable | | | function was defined in, or | | | | ``None`` if unavailable. | | @@ -1272,7 +1277,27 @@ Basic customization inheritance of :meth:`__hash__` will be blocked, just as if :attr:`__hash__` had been explicitly set to :const:`None`. - See also the :option:`-R` command-line option. + + .. note:: + + Note by default the :meth:`__hash__` values of str, bytes and datetime + objects are "salted" with an unpredictable random value. Although they + remain constant within an individual Python process, they are not + predictable between repeated invocations of Python. + + This is intended to provide protection against a denial-of-service caused + by carefully-chosen inputs that exploit the worst case performance of a + dict insertion, O(n^2) complexity. See + http://www.ocert.org/advisories/ocert-2011-003.html for details. + + Changing hash values affects the order in which keys are retrieved from a + dict. Note Python has never made guarantees about this ordering (and it + typically varies between 32-bit and 64-bit builds). + + See also :envvar:`PYTHONHASHSEED`. + + .. versionchanged:: 3.3 + Hash randomization is enabled by default. .. method:: object.__bool__(self) @@ -1353,7 +1378,8 @@ access (use of, assignment to, or deletion of ``x.name``) for class instances. .. method:: object.__dir__(self) - Called when :func:`dir` is called on the object. A list must be returned. + Called when :func:`dir` is called on the object. A sequence must be + returned. :func:`dir` converts the returned sequence to a list and sorts it. .. _descriptors: |