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+
+:mod:`numbers` --- Numeric abstract base classes
+================================================
+
+.. module:: numbers
+   :synopsis: Numeric abstract base classes (Complex, Real, Integral, etc.).
+
+The :mod:`numbers` module (:pep:`3141`) defines a hierarchy of numeric abstract
+base classes which progressively define more operations. These concepts also
+provide a way to distinguish exact from inexact types. None of the types defined
+in this module can be instantiated.
+
+
+.. class:: Number
+
+   The root of the numeric hierarchy. If you just want to check if an argument
+   *x* is a number, without caring what kind, use ``isinstance(x, Number)``.
+
+
+Exact and inexact operations
+----------------------------
+
+.. class:: Exact
+
+   Subclasses of this type have exact operations.
+
+   As long as the result of a homogenous operation is of the same type, you can
+   assume that it was computed exactly, and there are no round-off errors. Laws
+   like commutativity and associativity hold.
+
+
+.. class:: Inexact
+
+   Subclasses of this type have inexact operations.
+
+   Given X, an instance of :class:`Inexact`, it is possible that ``(X + -X) + 3
+   == 3``, but ``X + (-X + 3) == 0``. The exact form this error takes will vary
+   by type, but it's generally unsafe to compare this type for equality.
+
+
+The numeric tower
+-----------------
+
+.. class:: Complex
+
+   Subclasses of this type describe complex numbers and include the operations
+   that work on the builtin :class:`complex` type. These are: conversions to
+   :class:`complex` and :class:`bool`, :attr:`.real`, :attr:`.imag`, ``+``,
+   ``-``, ``*``, ``/``, :func:`abs`, :meth:`conjugate`, ``==``, and ``!=``. All
+   except ``-`` and ``!=`` are abstract.
+
+.. attribute:: Complex.real
+
+   Abstract. Retrieves the :class:`Real` component of this number.
+
+.. attribute:: Complex.imag
+
+   Abstract. Retrieves the :class:`Real` component of this number.
+
+.. method:: Complex.conjugate()
+
+   Abstract. Returns the complex conjugate. For example, ``(1+3j).conjugate() ==
+   (1-3j)``.
+
+.. class:: Real
+
+   To :class:`Complex`, :class:`Real` adds the operations that work on real
+   numbers.
+
+   In short, those are: a conversion to :class:`float`, :func:`trunc`,
+   :func:`round`, :func:`math.floor`, :func:`math.ceil`, :func:`divmod`, ``//``,
+   ``%``, ``<``, ``<=``, ``>``, and ``>=``.
+
+   Real also provides defaults for :func:`complex`, :attr:`Complex.real`,
+   :attr:`Complex.imag`, and :meth:`Complex.conjugate`.
+
+
+.. class:: Rational
+
+   Subtypes both :class:`Real` and :class:`Exact`, and adds
+   :attr:`Rational.numerator` and :attr:`Rational.denominator` properties, which
+   should be in lowest terms. With these, it provides a default for
+   :func:`float`.
+
+.. attribute:: Rational.numerator
+
+   Abstract.
+
+.. attribute:: Rational.denominator
+
+   Abstract.
+
+
+.. class:: Integral
+
+   Subtypes :class:`Rational` and adds a conversion to :class:`long`, the
+   3-argument form of :func:`pow`, and the bit-string operations: ``<<``,
+   ``>>``, ``&``, ``^``, ``|``, ``~``. Provides defaults for :func:`float`,
+   :attr:`Rational.numerator`, and :attr:`Rational.denominator`.