Metadata-Version: 1.1
Name: namedlist
Version: 0.4
Summary: Similar to namedtuple, but instances are mutable.
Home-page: https://bitbucket.org/ericvsmith/namedlist
Author: Eric V. Smith
Author-email: eric@trueblade.com
License: Apache License Version 2.0
Description: ===========
        namedlist
        ===========
        
        Overview
        ========
        
        namedlist provides a factory function, named
        namedlist.namedlist. It is similar to collections.namedtuple, with
        the following differences:
        
        * namedlist instances are mutable.
        
        * namedlist supports per-field default values.
        
        * namedlist supports an optional default value, to be used by all
          fields do not have an explicit default value.
        
        Typical usage
        =============
        
        You can use namedlist like a mutable namedtuple::
        
            >>> from namedlist import namedlist
        
            >>> Point = namedlist('Point', 'x y')
            >>> p = Point(1, 3)
            >>> p.x = 2
            >>> assert p.x == 2
            >>> assert p.y == 3
        
        Or, you can specify a default value for all fields::
        
            >>> Point = namedlist('Point', 'x y', default=3)
            >>> p = Point(y=2)
            >>> assert p.x == 3
            >>> assert p.y == 2
        
        Or, you can specify per-field default values::
        
            >>> Point = namedlist('Point', [('x', 0), ('y', 100)])
            >>> p = Point()
            >>> assert p.x == 0
            >>> assert p.y == 100
        
        You can also specify the per-field defaults with a mapping, instead
        of an iterable. Note that this is only useful with an ordered
        mapping, such as an OrderedDict::
        
            >>> from collections import OrderedDict
            >>> Point = namedlist('Point', OrderedDict((('y', 0),
            ...                                         ('x', 100))))
            >>> p = Point()
            >>> p
            Point(y=0, x=100)
        
        The default value will only be used if it is provided and a per-field
        default is not used::
        
            >>> Point = namedlist('Point', ['x', ('y', 100)], default=10)
            >>> p = Point()
            >>> assert p.x == 10
            >>> assert p.y == 100
        
        If you use a mapping, the value NO_DEFAULT is convenient to specify
        that a field uses the default value::
        
            >>> from namedlist import NO_DEFAULT
            >>> Point = namedlist('Point', OrderedDict((('y', NO_DEFAULT),
            ...                                         ('x', 100))),
            ...                            default=5)
            >>> p = Point()
            >>> assert p.x == 100
            >>> assert p.y == 5
        
        
        Creating types
        ==============
        
        Specifying Fields
        -----------------
        
        Fields can be specified as in namedtuple: as either a string specifing
        the field names, or as a iterable of field names. These two uses are
        equivalent::
        
            >>> Point = namedlist('Point', 'x y')
            >>> Point = namedlist('Point', ['x', 'y'])
        
        If using a string, commas are first converted to spaces. So these are
        equivalent::
        
            >>> Point = namedlist('Point', 'x y')
            >>> Point = namedlist('Point', 'x,y')
        
        
        Specifying Defaults
        -------------------
        
        Per-field defaults can be specified by supplying a 2-tuple (name,
        default_value) instead of just a string for the field name. This is
        only supported when you specify a list of field names::
        
            >>> Point = namedlist('Point', [('x', 0), ('y', 0)])
            >>> p = Point(3)
            >>> assert p.x == 3
            >>> assert p.y == 0
        
        In addition to, or instead of, these per-field defaults, you can also
        specify a default value which is used when no per-field default value
        is specified::
        
            >>> Point = namedlist('Point', 'x y z', default=0)
            >>> p = Point(y=3)
            >>> assert p.x == 0
            >>> assert p.y == 3
            >>> assert p.z == 0
        
            >>> Point = namedlist('Point', [('x', 0), 'y', ('z', 0)], default=4)
            >>> p = Point(z=2)
            >>> assert p.x == 0
            >>> assert p.y == 4
            >>> assert p.z == 2
        
        In addition to supplying the field names as an iterable of 2-tuples,
        you can also specify a mapping. The keys will be the field names, and
        the values will be the per-field default values. This is most useful
        with an OrderedDict, as the order of the fields will then be
        deterministic.  The module variable NO_DEFAULT can be specified if you
        want a field to use the per-type default value instead of specifying
        it with a field::
        
            >>> Point = namedlist('Point', OrderedDict((('x', 0),
            ...                                         ('y', NO_DEFAULT),
            ...                                         ('z', 0),
            ...                                         )),
            ...                            default=4)
            >>> p = Point(z=2)
            >>> assert p.x == 0
            >>> assert p.y == 4
            >>> assert p.z == 2
        
        Writing to values
        -----------------
        
        The objects returned by the factory function are fully writable, unlike
        the tuple-derived classes returned by namedtuple::
        
            >>> Point = namedlist('Point', 'x y')
            >>> p = Point(1, 2)
            >>> p.y = 4
            >>> assert p.x == 1
            >>> assert p.y == 4
        
        
        Specifying __slots__
        --------------------
        
        By default, the returned class sets __slots__ which is initialized to
        the field names. While this decreases memory usage by eliminating the
        instance dict, it also means that you cannot create new instance
        members.
        
        To change this behavior, specify use_slots=False when creating the
        namedlist::
        
            >>> Point = namedlist('Point', 'x y', use_slots=False)
            >>> p = Point(0, 1)
            >>> p.z = 2
            >>> assert p.x == 0
            >>> assert p.y == 1
            >>> assert p.z == 2
        
        
        Additional class members
        ------------------------
        
        namedlist classes contain these members:
        
        * _asdict(): Returns a dict which maps field names to their
          corresponding values.
        
        * _fields: Tuple of strings listing the field names. Useful for introspection.
        
        
        Renaming invalid field names
        ----------------------------
        
        This functionality is identical to namedtuple. If you specify
        rename=True, then any invalid field names are changed to _0, _1,
        etc. Reasons for a field name to be invalid are:
        
        * Zero length strings.
        
        * Containing characters other than alphanumerics and underscores.
        
        * A conflict with a Python reserved identifier.
        
        * Beginning with a digit.
        
        * Beginning with an underscore.
        
        * Using the same field name more than once.
        
        For example::
        
            >>> Point = namedlist('Point', 'x x for', rename=True)
            >>> assert Point._fields == ('x', '_1', '_2')
        
        
        Mutable default values
        ----------------------
        
        Be aware of creating mutable default values. Due to the way Python
        handles default values, each instance of a namedlist will share the
        default. This is especially problematic with default values that are
        lists. For example::
        
            >>> A = namedlist('A', [('x', [])])
            >>> a = A()
            >>> a.x.append(4)
            >>> b = A()
            >>> assert b.x == [4]
        
        This is probably not the desired behavior, so see the next section.
        
        
        Specifying a factory function for default values
        ------------------------------------------------
        
        You can supply a zero-argument callable for a default, by wrapping it
        in a FACTORY call. The only change in this example is to change the
        default from `[]` to `FACTORY(list)`. But note that `b.x` is a new
        list object, not shared with `a.x`::
        
            >>> from namedlist import FACTORY
            >>> A = namedlist('A', [('x', FACTORY(list))])
            >>> a = A()
            >>> a.x.append(4)
            >>> b = A()
            >>> assert b.x == []
        
        Every time a new instance is created, your callable (in this case,
        `list`), will be called to produce a new instance for the default
        value.
        
        Iterating over instances
        ------------------------
        
        Because instances are iterable (like lists), iteration works the same way. Values are returned in definition order::
        
            >>> Point = namedlist('Point', 'x y z t')
            >>> p = Point(1.0, 42.0, 3.14, 2.71828)
            >>> for value in p:
            ...    print(value)
            1.0
            42.0
            3.14
            2.71828
        
        Creating and using instances
        ============================
        
        Because the type returned by namedlist is a normal Python class, you
        create instances as you would with any Python class.
        
        
        Change log
        ==========
        
        0.4 2014-02-04 Eric V. Smith
        ----------------------------
        
        * Add docstring (issue #7).
        
        * Fixed README.txt typos (thanks pombredanne on bitbucket).
        
        0.3 2014-01-29 Eric V. Smith
        ----------------------------
        
        * Removed documentation left over from recordtype.
        
        * Make instances unhashable (issue #2).
        
        * For python3, use str.isidentifier (issue #1).
        
        * Reorganize code for name checking. No functional changes.
        
        * Make instances iterable (issue #3).
        
        * Add collections.Sequence ABC (issue #4).
        
        * Have "python setup.py test" also run doctests (issue #5).
        
        0.2 2014-01-28 Eric V. Smith
        ----------------------------
        
        * Added MANIFEST.in.
        
        * Hopefully fixed a problem with .rst formatting in CHANGES.txt.
        
        0.1 2014-01-28 Eric V. Smith
        ----------------------------
        
        * Initial release.
        
        * Based off my recordtype project, but uses ast generation instead of
          building up a string and exec-ing it. This has a number of advantages:
        
          - Supporting both python2 and python3 is easier. exec has the
            anti-feature of having different syntax in the two languages.
        
          - Adding additional features is easier, because I can write in real
            Python instead of having to write the string version, and deal
            with all of the escaping and syntax errors.
        
        * Added FACTORY, to allow namedlist to work even with mutable defaults.
        
Platform: UNKNOWN
Classifier: Development Status :: 5 - Production/Stable
Classifier: Intended Audience :: Developers
Classifier: License :: OSI Approved :: Apache Software License
Classifier: Topic :: Software Development :: Libraries :: Python Modules
Classifier: Programming Language :: Python :: 2.7
Classifier: Programming Language :: Python :: 3.3
