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diff --git a/Doc/glossary.rst b/Doc/glossary.rst index eb72558ecc..41228cd0e0 100644 --- a/Doc/glossary.rst +++ b/Doc/glossary.rst @@ -58,11 +58,14 @@ Glossary bytecode Python source code is compiled into bytecode, the internal representation - of a Python program in the interpreter. The bytecode is also cached in - ``.pyc`` and ``.pyo`` files so that executing the same file is faster the - second time (recompilation from source to bytecode can be avoided). This - "intermediate language" is said to run on a :term:`virtual machine` - that executes the machine code corresponding to each bytecode. + of a Python program in the CPython interpreter. The bytecode is also + cached in ``.pyc`` and ``.pyo`` files so that executing the same file is + faster the second time (recompilation from source to bytecode can be + avoided). This "intermediate language" is said to run on a + :term:`virtual machine` that executes the machine code corresponding to + each bytecode. Do note that bytecodes are not expected to work between + different Python virtual machines, nor to be stable between Python + releases. A list of bytecode instructions can be found in the documentation for :ref:`the dis module <bytecodes>`. @@ -128,8 +131,9 @@ Glossary def f(...): ... - See :ref:`the documentation for function definition <function>` for more - about decorators. + The same concept exists for classes, but is less commonly used there. See + the documentation for :ref:`function definitions <function>` and + :ref:`class definitions <class>` for more about decorators. descriptor Any *new-style* object which defines the methods :meth:`__get__`, @@ -165,8 +169,8 @@ Glossary well-designed code improves its flexibility by allowing polymorphic substitution. Duck-typing avoids tests using :func:`type` or :func:`isinstance`. (Note, however, that duck-typing can be complemented - with :term:`abstract base class`\ es.) Instead, it typically employs - :func:`hasattr` tests or :term:`EAFP` programming. + with :term:`abstract base classes <abstract base class>`.) Instead, it + typically employs :func:`hasattr` tests or :term:`EAFP` programming. EAFP Easier to ask for forgiveness than permission. This common Python coding @@ -178,17 +182,34 @@ Glossary expression A piece of syntax which can be evaluated to some value. In other words, - an expression is an accumulation of expression elements like literals, names, - attribute access, operators or function calls which all return a value. - In contrast to many other languages, not all language constructs are expressions. - There are also :term:`statement`\s which cannot be used as expressions, - such as :keyword:`print` or :keyword:`if`. Assignments are also statements, - not expressions. + an expression is an accumulation of expression elements like literals, + names, attribute access, operators or function calls which all return a + value. In contrast to many other languages, not all language constructs + are expressions. There are also :term:`statement`\s which cannot be used + as expressions, such as :keyword:`print` or :keyword:`if`. Assignments + are also statements, not expressions. extension module A module written in C or C++, using Python's C API to interact with the core and with user code. + file object + An object exposing a file-oriented API (with methods such as + :meth:`read()` or :meth:`write()`) to an underlying resource. Depending + on the way it was created, a file object can mediate access to a real + on-disk file or to another other type of storage or communication device + (for example standard input/output, in-memory buffers, sockets, pipes, + etc.). File objects are also called :dfn:`file-like objects` or + :dfn:`streams`. + + There are actually three categories of file objects: raw binary files, + buffered binary files and text files. Their interfaces are defined in the + :mod:`io` module. The canonical way to create a file object is by using + the :func:`open` function. + + file-like object + A synonym for :term:`file object`. + finder An object that tries to find the :term:`loader` for a module. It must implement a method named :meth:`find_module`. See :pep:`302` for @@ -335,7 +356,7 @@ Glossary slowly. See also :term:`interactive`. iterable - A container object capable of returning its members one at a + An object capable of returning its members one at a time. Examples of iterables include all sequence types (such as :class:`list`, :class:`str`, and :class:`tuple`) and some non-sequence types like :class:`dict` and :class:`file` and objects of any classes you @@ -404,6 +425,12 @@ Glossary the :term:`EAFP` approach and is characterized by the presence of many :keyword:`if` statements. + In a multi-threaded environment, the LBYL approach can risk introducing a + race condition between "the looking" and "the leaping". For example, the + code, ``if key in mapping: return mapping[key]`` can fail if another + thread removes *key* from *mapping* after the test, but before the lookup. + This issue can be solved with locks or by using the EAFP approach. + list A built-in Python :term:`sequence`. Despite its name it is more akin to an array in other languages than to a linked list since access to @@ -424,7 +451,8 @@ Glossary mapping A container object that supports arbitrary key lookups and implements the - methods specified in the :class:`Mapping` or :class:`MutableMapping` + methods specified in the :class:`~collections.Mapping` or + :class:`~collections.MutableMapping` :ref:`abstract base classes <collections-abstract-base-classes>`. Examples include :class:`dict`, :class:`collections.defaultdict`, :class:`collections.OrderedDict` and :class:`collections.Counter`. @@ -448,6 +476,14 @@ Glossary its first :term:`argument` (which is usually called ``self``). See :term:`function` and :term:`nested scope`. + method resolution order + Method Resolution Order is the order in which base classes are searched + for a member during lookup. See `The Python 2.3 Method Resolution Order + <http://www.python.org/download/releases/2.3/mro/>`_. + + MRO + See :term:`method resolution order`. + mutable Mutable objects can change their value but keep their :func:`id`. See also :term:`immutable`. @@ -480,10 +516,11 @@ Glossary nested scope The ability to refer to a variable in an enclosing definition. For instance, a function defined inside another function can refer to - variables in the outer function. Note that nested scopes work only for - reference and not for assignment which will always write to the innermost - scope. In contrast, local variables both read and write in the innermost - scope. Likewise, global variables read and write to the global namespace. + variables in the outer function. Note that nested scopes by default work + only for reference and not for assignment. Local variables both read and + write in the innermost scope. Likewise, global variables read and write + to the global namespace. The :keyword:`nonlocal` allows writing to outer + scopes. new-style class Any class which inherits from :class:`object`. This includes all built-in @@ -506,9 +543,9 @@ Glossary :term:`argument`. Python 3000 - Nickname for the next major Python version, 3.0 (coined long ago - when the release of version 3 was something in the distant future.) This - is also abbreviated "Py3k". + Nickname for the Python 3.x release line (coined long ago when the release + of version 3 was something in the distant future.) This is also + abbreviated "Py3k". Pythonic An idea or piece of code which closely follows the most common idioms @@ -531,7 +568,7 @@ Glossary object drops to zero, it is deallocated. Reference counting is generally not visible to Python code, but it is a key element of the :term:`CPython` implementation. The :mod:`sys` module defines a - :func:`getrefcount` function that programmers can call to return the + :func:`~sys.getrefcount` function that programmers can call to return the reference count for a particular object. __slots__ @@ -567,7 +604,15 @@ Glossary statement A statement is part of a suite (a "block" of code). A statement is either an :term:`expression` or a one of several constructs with a keyword, such - as :keyword:`if`, :keyword:`while` or :keyword:`print`. + as :keyword:`if`, :keyword:`while` or :keyword:`for`. + + struct sequence + A tuple with named elements. Struct sequences expose an interface similiar + to :term:`named tuple` in that elements can either be accessed either by + index or as an attribute. However, they do not have any of the named tuple + methods like :meth:`~collections.somenamedtuple._make` or + :meth:`~collections.somenamedtuple._asdict`. Examples of struct sequences + include :data:`sys.float_info` and the return value of :func:`os.stat`. triple-quoted string A string which is bound by three instances of either a quotation mark |