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authorGeorg Brandl <georg@python.org>2007-09-28 13:39:25 (GMT)
committerGeorg Brandl <georg@python.org>2007-09-28 13:39:25 (GMT)
commit905ec32892b7b87e6a6c1f7f030ac95fba4d5c0e (patch)
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parent2d2590de49081eea38152e0a25496069a059c69e (diff)
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#1219: py3k cleanup in standard types docs.
Diffstat (limited to 'Doc/library')
-rw-r--r--Doc/library/stdtypes.rst232
1 files changed, 103 insertions, 129 deletions
diff --git a/Doc/library/stdtypes.rst b/Doc/library/stdtypes.rst
index 136a8d5..a020700 100644
--- a/Doc/library/stdtypes.rst
+++ b/Doc/library/stdtypes.rst
@@ -10,13 +10,6 @@ Built-in Types
The following sections describe the standard types that are built into the
interpreter.
-.. note::
-
- Historically (until release 2.2), Python's built-in types have differed from
- user-defined types because it was not possible to use the built-in types as the
- basis for object-oriented inheritance. This limitation no longer
- exists.
-
.. index:: pair: built-in; types
The principal built-in types are numerics, sequences, mappings, files, classes,
@@ -129,8 +122,8 @@ Comparisons
.. index:: pair: chaining; comparisons
-Comparison operations are supported by all objects. They all have the same
-priority (which is higher than that of the Boolean operations). Comparisons can
+There are eight comparison operations in Python. They all have the same
+priority (which is higher than that of the Boolean operations). Comparisons can
be chained arbitrarily; for example, ``x < y <= z`` is equivalent to ``x < y and
y <= z``, except that *y* is evaluated only once (but in both cases *z* is not
evaluated at all when ``x < y`` is found to be false).
@@ -172,24 +165,35 @@ This table summarizes the comparison operations:
pair: object; numeric
pair: objects; comparing
-Objects of different types, except different numeric types and different string
-types, never compare equal; such objects are ordered consistently but
-arbitrarily (so that sorting a heterogeneous array yields a consistent result).
+Objects of different types, except different numeric types, never compare equal.
Furthermore, some types (for example, file objects) support only a degenerate
-notion of comparison where any two objects of that type are unequal. Again,
-such objects are ordered arbitrarily but consistently. The ``<``, ``<=``, ``>``
-and ``>=`` operators will raise a :exc:`TypeError` exception when any operand is
-a complex number.
-
-.. index:: single: __cmp__() (instance method)
+notion of comparison where any two objects of that type are unequal. The ``<``,
+``<=``, ``>`` and ``>=`` operators will raise a :exc:`TypeError` exception when
+any operand is a complex number, the objects are of different types that cannot
+be compared, or other cases where there is no defined ordering.
+
+.. index::
+ single: __cmp__() (instance method)
+ single: __eq__() (instance method)
+ single: __ne__() (instance method)
+ single: __lt__() (instance method)
+ single: __le__() (instance method)
+ single: __gt__() (instance method)
+ single: __ge__() (instance method)
Instances of a class normally compare as non-equal unless the class defines the
-:meth:`__cmp__` method. Refer to :ref:`customization`) for information on the
-use of this method to effect object comparisons.
+:meth:`__eq__` or :meth:`__cmp__` method.
+
+Instances of a class cannot be ordered with respect to other instances of the
+same class, or other types of object, unless the class defines enough of the
+methods :meth:`__cmp__`, :meth:`__lt__`, :meth:`__le__`, :meth:`__gt__`, and
+:meth:`__ge__` (in general, either :meth:`__cmp__` or both :meth:`__lt__` and
+:meth:`__eq__` are sufficient, if you want the conventional meanings of the
+comparison operators).
-**Implementation note:** Objects of different types except numbers are ordered
-by their type names; objects of the same types that don't support proper
-comparison are ordered by their address.
+The behavior of the :keyword:`is` and :keyword:`is not` operators cannot be
+customized; also they can be applied to any two objects and never raise an
+exception.
.. index::
operator: in
@@ -201,27 +205,22 @@ supported only by sequence types (below).
.. _typesnumeric:
-Numeric Types --- :class:`int`, :class:`float`, :class:`long`, :class:`complex`
-===============================================================================
+Numeric Types --- :class:`int`, :class:`float`, :class:`complex`
+================================================================
.. index::
object: numeric
object: Boolean
object: integer
- object: long integer
object: floating point
object: complex number
pair: C; language
-There are four distinct numeric types: :dfn:`plain integers`, :dfn:`long
-integers`, :dfn:`floating point numbers`, and :dfn:`complex numbers`. In
-addition, Booleans are a subtype of plain integers. Plain integers (also just
-called :dfn:`integers`) are implemented using :ctype:`long` in C, which gives
-them at least 32 bits of precision (``sys.maxint`` is always set to the maximum
-plain integer value for the current platform, the minimum value is
-``-sys.maxint - 1``). Long integers have unlimited precision. Floating point
-numbers are implemented using :ctype:`double` in C. All bets on their precision
-are off unless you happen to know the machine you are working with.
+There are three distinct numeric types: :dfn:`integers`, :dfn:`floating point
+numbers`, and :dfn:`complex numbers`. In addition, Booleans are a subtype of
+plain integers. Integers have unlimited precision. loating point numbers are
+implemented using :ctype:`double` in C. All bets on their precision are off
+unless you happen to know the machine you are working with.
Complex numbers have a real and imaginary part, which are each implemented using
:ctype:`double` in C. To extract these parts from a complex number *z*, use
@@ -230,21 +229,19 @@ Complex numbers have a real and imaginary part, which are each implemented using
.. index::
pair: numeric; literals
pair: integer; literals
- triple: long; integer; literals
pair: floating point; literals
pair: complex number; literals
pair: hexadecimal; literals
pair: octal; literals
+ pair: binary: literals
Numbers are created by numeric literals or as the result of built-in functions
-and operators. Unadorned integer literals (including hex and octal numbers)
-yield plain integers unless the value they denote is too large to be represented
-as a plain integer, in which case they yield a long integer. Integer literals
-with an ``'L'`` or ``'l'`` suffix yield long integers (``'L'`` is preferred
-because ``1l`` looks too much like eleven!). Numeric literals containing a
-decimal point or an exponent sign yield floating point numbers. Appending
-``'j'`` or ``'J'`` to a numeric literal yields a complex number with a zero real
-part. A complex numeric literal is the sum of a real and an imaginary part.
+and operators. Unadorned integer literals (including hex, octal and binary
+numbers) yield integers. Numeric literals containing a decimal point or an
+exponent sign yield floating point numbers. Appending ``'j'`` or ``'J'`` to a
+numeric literal yields an imaginary number (a complex number with a zero real
+part) which you can add to an integer or float to get a complex number with real
+and imaginary parts.
.. index::
single: arithmetic
@@ -255,58 +252,55 @@ part. A complex numeric literal is the sum of a real and an imaginary part.
Python fully supports mixed arithmetic: when a binary arithmetic operator has
operands of different numeric types, the operand with the "narrower" type is
-widened to that of the other, where plain integer is narrower than long integer
-is narrower than floating point is narrower than complex. Comparisons between
-numbers of mixed type use the same rule. [#]_ The constructors :func:`int`,
-:func:`long`, :func:`float`, and :func:`complex` can be used to produce numbers
-of a specific type.
+widened to that of the other, where integer is narrower than floating point,
+which is narrower than complex. Comparisons between numbers of mixed type use
+the same rule. [#]_ The constructors :func:`int`, :func:`float`, and
+:func:`complex` can be used to produce numbers of a specific type.
All numeric types (except complex) support the following operations, sorted by
ascending priority (operations in the same box have the same priority; all
numeric operations have a higher priority than comparison operations):
-+--------------------+---------------------------------+--------+
-| Operation | Result | Notes |
-+====================+=================================+========+
-| ``x + y`` | sum of *x* and *y* | |
-+--------------------+---------------------------------+--------+
-| ``x - y`` | difference of *x* and *y* | |
-+--------------------+---------------------------------+--------+
-| ``x * y`` | product of *x* and *y* | |
-+--------------------+---------------------------------+--------+
-| ``x / y`` | quotient of *x* and *y* | \(1) |
-+--------------------+---------------------------------+--------+
-| ``x // y`` | (floored) quotient of *x* and | \(5) |
-| | *y* | |
-+--------------------+---------------------------------+--------+
-| ``x % y`` | remainder of ``x / y`` | \(4) |
-+--------------------+---------------------------------+--------+
-| ``-x`` | *x* negated | |
-+--------------------+---------------------------------+--------+
-| ``+x`` | *x* unchanged | |
-+--------------------+---------------------------------+--------+
-| ``abs(x)`` | absolute value or magnitude of | |
-| | *x* | |
-+--------------------+---------------------------------+--------+
-| ``int(x)`` | *x* converted to integer | \(2) |
-+--------------------+---------------------------------+--------+
-| ``long(x)`` | *x* converted to long integer | \(2) |
-+--------------------+---------------------------------+--------+
-| ``float(x)`` | *x* converted to floating point | |
-+--------------------+---------------------------------+--------+
-| ``complex(re,im)`` | a complex number with real part | |
-| | *re*, imaginary part *im*. | |
-| | *im* defaults to zero. | |
-+--------------------+---------------------------------+--------+
-| ``c.conjugate()`` | conjugate of the complex number | |
-| | *c* | |
-+--------------------+---------------------------------+--------+
-| ``divmod(x, y)`` | the pair ``(x // y, x % y)`` | (3)(4) |
-+--------------------+---------------------------------+--------+
-| ``pow(x, y)`` | *x* to the power *y* | |
-+--------------------+---------------------------------+--------+
-| ``x ** y`` | *x* to the power *y* | |
-+--------------------+---------------------------------+--------+
++---------------------+---------------------------------+-------+--------------------+
+| Operation | Result | Notes | Full documentation |
++==================== +=================================+=======+====================|
+| ``x + y`` | sum of *x* and *y* | | |
++---------------------+---------------------------------+-------+--------------------+
+| ``x - y`` | difference of *x* and *y* | | |
++---------------------+---------------------------------+-------+--------------------+
+| ``x * y`` | product of *x* and *y* | | |
++---------------------+---------------------------------+-------+--------------------+
+| ``x / y`` | quotient of *x* and *y* | | |
++---------------------+---------------------------------+-------+--------------------+
+| ``x // y`` | floored quotient of *x* and | \(1) | |
+| | *y* | | |
++---------------------+---------------------------------+-------+--------------------+
+| ``x % y`` | remainder of ``x / y`` | \(2) | |
++---------------------+---------------------------------+-------+--------------------+
+| ``-x`` | *x* negated | | |
++---------------------+---------------------------------+-------+--------------------+
+| ``+x`` | *x* unchanged | | |
++---------------------+---------------------------------+-------+--------------------+
+| ``abs(x)`` | absolute value or magnitude of | | :func:`abs` |
+| | *x* | | |
++---------------------+---------------------------------+-------+--------------------+
+| ``int(x)`` | *x* converted to integer | \(3) | :func:`int` |
++---------------------+---------------------------------+-------+--------------------+
+| ``float(x)`` | *x* converted to floating point | | :func:`float` |
++---------------------+---------------------------------+-------+--------------------+
+| ``complex(re, im)`` | a complex number with real part | | :func:`complex` |
+| | *re*, imaginary part *im*. | | |
+| | *im* defaults to zero. | | |
++---------------------+---------------------------------+-------+--------------------+
+| ``c.conjugate()`` | conjugate of the complex number | | |
+| | *c* | | |
++---------------------+---------------------------------+-------+--------------------+
+| ``divmod(x, y)`` | the pair ``(x // y, x % y)`` | \(2) | :func:`divmod` |
++---------------------+---------------------------------+-------+--------------------+
+| ``pow(x, y)`` | *x* to the power *y* | | :func:`pow` |
++---------------------+---------------------------------+-------+--------------------+
+| ``x ** y`` | *x* to the power *y* | | |
++---------------------+---------------------------------+-------+--------------------+
.. index::
triple: operations on; numeric; types
@@ -315,16 +309,16 @@ numeric operations have a higher priority than comparison operations):
Notes:
(1)
- .. index::
- pair: integer; division
- triple: long; integer; division
-
- For (plain or long) integer division, the result is an integer. The result is
- always rounded towards minus infinity: 1/2 is 0, (-1)/2 is -1, 1/(-2) is -1, and
- (-1)/(-2) is 0. Note that the result is a long integer if either operand is a
- long integer, regardless of the numeric value.
+ Also referred to as integer division. The resultant value is a whole
+ integer, though the result's type is not necessarily int. The result is
+ always rounded towards minus infinity: ``1//2`` is ``0``, ``(-1)//2`` is
+ ``-1``, ``1//(-2)`` is ``-1``, and ``(-1)//(-2)`` is ``0``.
(2)
+ Not for complex numbers. Instead convert to floats using :func:`abs` if
+ appropriate.
+
+(3)
.. index::
module: math
single: floor() (in module math)
@@ -336,19 +330,6 @@ Notes:
as in C; see functions :func:`floor` and :func:`ceil` in the :mod:`math` module
for well-defined conversions.
-(3)
- See :ref:`built-in-funcs` for a full description.
-
-(4)
- Complex floor division operator, modulo operator, and :func:`divmod`.
-
- .. deprecated:: 2.3
- Instead convert to float using :func:`abs` if appropriate.
-
-(5)
- Also referred to as integer division. The resultant value is a whole integer,
- though the result's type is not necessarily int.
-
.. % XXXJH exceptions: overflow (when? what operations?) zerodivision
@@ -359,10 +340,9 @@ Bit-string Operations on Integer Types
.. _bit-string-operations:
-Plain and long integer types support additional operations that make sense only
-for bit-strings. Negative numbers are treated as their 2's complement value
-(for long integers, this assumes a sufficiently large number of bits that no
-overflow occurs during the operation).
+Integers support additional operations that make sense only for bit-strings.
+Negative numbers are treated as their 2's complement value (this assumes a
+sufficiently large number of bits that no overflow occurs during the operation).
The priorities of the binary bit-wise operations are all lower than the numeric
operations and higher than the comparisons; the unary operation ``~`` has the
@@ -453,7 +433,7 @@ methods, which together form the :dfn:`iterator protocol`:
Python objects in the Python/C API.
-.. method:: iterator.next()
+.. method:: iterator.__next__()
Return the next item from the container. If there are no further items, raise
the :exc:`StopIteration` exception. This method corresponds to the
@@ -465,11 +445,9 @@ specific sequence types, dictionaries, and other more specialized forms. The
specific types are not important beyond their implementation of the iterator
protocol.
-The intention of the protocol is that once an iterator's :meth:`__next__` method
-raises :exc:`StopIteration`, it will continue to do so on subsequent calls.
-Implementations that do not obey this property are deemed broken. (This
-constraint was added in Python 2.3; in Python 2.2, various iterators are broken
-according to this rule.)
+Once an iterator's :meth:`__next__` method raises :exc:`StopIteration`, it must
+continue to do so on subsequent calls. Implementations that do not obey this
+property are deemed broken.
Python's generators provide a convenient way to implement the iterator protocol.
If a container object's :meth:`__iter__` method is implemented as a generator,
@@ -1140,13 +1118,9 @@ Notes:
decimal point and defaults to 6.
(5)
- The ``%r`` conversion was added in Python 2.0.
-
The precision determines the maximal number of characters used.
- The precision determines the maximal number of characters used.
-
Since Python strings have an explicit length, ``%s`` conversions do not assume
that ``'\0'`` is the end of the string.
@@ -1164,8 +1138,8 @@ Additional string operations are defined in standard modules :mod:`string` and
.. _typesseq-range:
-XRange Type
------------
+Range Type
+----------
.. index:: object: range
@@ -1174,7 +1148,7 @@ looping. The advantage of the :class:`range` type is that an :class:`range`
object will always take the same amount of memory, no matter the size of the
range it represents. There are no consistent performance advantages.
-XRange objects have very little behavior: they only support indexing, iteration,
+Range objects have very little behavior: they only support indexing, iteration,
and the :func:`len` function.