most significant flaws was that it's impossible to subclass Python types
implemented in C. In particular, it's not possible to subclass built-in types,
so you can't just subclass, say, lists in order to add a single useful method to
-them. The :mod:`UserList` module provides a class that supports all of the
+them. The :mod:`!UserList` module provides a class that supports all of the
methods of lists and that can be subclassed further, but there's lots of C code
-that expects a regular Python list and won't accept a :class:`UserList`
+that expects a regular Python list and won't accept a :class:`!UserList`
instance.
Python 2.2 fixes this, and in the process adds some exciting new capabilities.
* It's also possible to automatically call methods on accessing or setting an
instance attribute by using a new mechanism called :dfn:`properties`. Many uses
- of :meth:`__getattr__` can be rewritten to use properties instead, making the
+ of :meth:`!__getattr__` can be rewritten to use properties instead, making the
resulting code simpler and faster. As a small side benefit, attributes can now
have docstrings, too.
This means that :keyword:`class` statements that don't have any base classes are
always classic classes in Python 2.2. (Actually you can also change this by
-setting a module-level variable named :attr:`__metaclass__` --- see :pep:`253`
+setting a module-level variable named :attr:`!__metaclass__` --- see :pep:`253`
for the details --- but it's easier to just subclass :class:`object`.)
The type objects for the built-in types are available as built-ins, named using
123
To make the set of types complete, new type objects such as :func:`dict` and
-:func:`file` have been added. Here's a more interesting example, adding a
-:meth:`lock` method to file objects::
+:func:`!file` have been added. Here's a more interesting example, adding a
+:meth:`!lock` method to file objects::
class LockableFile(file):
def lock (self, operation, length=0, start=0, whence=0):
The now-obsolete :mod:`!posixfile` module contained a class that emulated all of
a file object's methods and also added a :meth:`!lock` method, but this class
couldn't be passed to internal functions that expected a built-in file,
-something which is possible with our new :class:`LockableFile`.
+something which is possible with our new :class:`!LockableFile`.
Descriptors
In previous versions of Python, there was no consistent way to discover what
attributes and methods were supported by an object. There were some informal
-conventions, such as defining :attr:`__members__` and :attr:`__methods__`
+conventions, such as defining :attr:`!__members__` and :attr:`!__methods__`
attributes that were lists of names, but often the author of an extension type
or a class wouldn't bother to define them. You could fall back on inspecting
the :attr:`~object.__dict__` of an object, but when class inheritance or an arbitrary
-:meth:`__getattr__` hook were in use this could still be inaccurate.
+:meth:`!__getattr__` hook were in use this could still be inaccurate.
The one big idea underlying the new class model is that an API for describing
the attributes of an object using :dfn:`descriptors` has been formalized.
* :attr:`~definition.__name__` is the attribute's name.
-* :attr:`__doc__` is the attribute's docstring.
+* :attr:`!__doc__` is the attribute's docstring.
* ``__get__(object)`` is a method that retrieves the attribute value from
*object*.
descriptor = obj.__class__.x
descriptor.__get__(obj)
-For methods, :meth:`descriptor.__get__` returns a temporary object that's
+For methods, :meth:`!descriptor.__get__` returns a temporary object that's
callable, and wraps up the instance and the method to be called on it. This is
also why static methods and class methods are now possible; they have
descriptors that wrap up just the method, or the method and the class. As a
...
g = classmethod(g)
-The :func:`staticmethod` function takes the function :func:`f`, and returns it
+The :func:`staticmethod` function takes the function :func:`!f`, and returns it
wrapped up in a descriptor so it can be stored in the class object. You might
expect there to be special syntax for creating such methods (``def static f``,
``defstatic f()``, or something like that) but no such syntax has been defined
f = eiffelmethod(f, pre_f, post_f)
-Note that a person using the new :func:`eiffelmethod` doesn't have to understand
+Note that a person using the new :func:`!eiffelmethod` doesn't have to understand
anything about descriptors. This is why I think the new features don't increase
the basic complexity of the language. There will be a few wizards who need to
-know about it in order to write :func:`eiffelmethod` or the ZODB or whatever,
+know about it in order to write :func:`!eiffelmethod` or the ZODB or whatever,
but most users will just write code on top of the resulting libraries and ignore
the implementation details.
The lookup rule for classic classes is simple but not very smart; the base
classes are searched depth-first, going from left to right. A reference to
-:meth:`D.save` will search the classes :class:`D`, :class:`B`, and then
-:class:`A`, where :meth:`save` would be found and returned. :meth:`C.save`
-would never be found at all. This is bad, because if :class:`C`'s :meth:`save`
-method is saving some internal state specific to :class:`C`, not calling it will
+:meth:`!D.save` will search the classes :class:`!D`, :class:`!B`, and then
+:class:`!A`, where :meth:`!save` would be found and returned. :meth:`!C.save`
+would never be found at all. This is bad, because if :class:`!C`'s :meth:`!save`
+method is saving some internal state specific to :class:`!C`, not calling it will
result in that state never getting saved.
New-style classes follow a different algorithm that's a bit more complicated to
#. List all the base classes, following the classic lookup rule and include a
class multiple times if it's visited repeatedly. In the above example, the list
- of visited classes is [:class:`D`, :class:`B`, :class:`A`, :class:`C`,
- :class:`A`].
+ of visited classes is [:class:`!D`, :class:`!B`, :class:`!A`, :class:`!C`,
+ :class:`!A`].
#. Scan the list for duplicated classes. If any are found, remove all but one
occurrence, leaving the *last* one in the list. In the above example, the list
- becomes [:class:`D`, :class:`B`, :class:`C`, :class:`A`] after dropping
+ becomes [:class:`!D`, :class:`!B`, :class:`!C`, :class:`!A`] after dropping
duplicates.
-Following this rule, referring to :meth:`D.save` will return :meth:`C.save`,
+Following this rule, referring to :meth:`!D.save` will return :meth:`!C.save`,
which is the behaviour we're after. This lookup rule is the same as the one
followed by Common Lisp. A new built-in function, :func:`super`, provides a way
to get at a class's superclasses without having to reimplement Python's
algorithm. The most commonly used form will be ``super(class, obj)``, which
returns a bound superclass object (not the actual class object). This form
will be used in methods to call a method in the superclass; for example,
-:class:`D`'s :meth:`save` method would look like this::
+:class:`!D`'s :meth:`!save` method would look like this::
class D (B,C):
def save (self):
----------------
A fair number of sophisticated Python classes define hooks for attribute access
-using :meth:`__getattr__`; most commonly this is done for convenience, to make
+using :meth:`~object.__getattr__`; most commonly this is done for convenience, to make
code more readable by automatically mapping an attribute access such as
``obj.parent`` into a method call such as ``obj.get_parent``. Python 2.2 adds
some new ways of controlling attribute access.
New-style classes also support a new method,
``__getattribute__(attr_name)``. The difference between the two methods is
-that :meth:`__getattribute__` is *always* called whenever any attribute is
-accessed, while the old :meth:`__getattr__` is only called if ``foo`` isn't
+that :meth:`~object.__getattribute__` is *always* called whenever any attribute is
+accessed, while the old :meth:`~object.__getattr__` is only called if ``foo`` isn't
found in the instance's dictionary.
However, Python 2.2's support for :dfn:`properties` will often be a simpler way
-to trap attribute references. Writing a :meth:`__getattr__` method is
+to trap attribute references. Writing a :meth:`!__getattr__` method is
complicated because to avoid recursion you can't use regular attribute accesses
inside them, and instead have to mess around with the contents of
-:attr:`~object.__dict__`. :meth:`__getattr__` methods also end up being called by Python
-when it checks for other methods such as :meth:`__repr__` or :meth:`__coerce__`,
+:attr:`~object.__dict__`. :meth:`~object.__getattr__` methods also end up being called by Python
+when it checks for other methods such as :meth:`~object.__repr__` or :meth:`!__coerce__`,
and so have to be written with this in mind. Finally, calling a function on
every attribute access results in a sizable performance loss.
:class:`property` is a new built-in type that packages up three functions that
get, set, or delete an attribute, and a docstring. For example, if you want to
-define a :attr:`size` attribute that's computed, but also settable, you could
+define a :attr:`!size` attribute that's computed, but also settable, you could
write::
class C(object):
"Storage size of this instance")
That is certainly clearer and easier to write than a pair of
-:meth:`__getattr__`/:meth:`__setattr__` methods that check for the :attr:`size`
+:meth:`!__getattr__`/:meth:`!__setattr__` methods that check for the :attr:`!size`
attribute and handle it specially while retrieving all other attributes from the
-instance's :attr:`~object.__dict__`. Accesses to :attr:`size` are also the only ones
+instance's :attr:`~object.__dict__`. Accesses to :attr:`!size` are also the only ones
which have to perform the work of calling a function, so references to other
attributes run at their usual speed.
iterator that will invoke the callable object *C* until it returns *sentinel* to
signal that the iterator is done.
-Python classes can define an :meth:`__iter__` method, which should create and
+Python classes can define an :meth:`!__iter__` method, which should create and
return a new iterator for the object; if the object is its own iterator, this
method can just return ``self``. In particular, iterators will usually be their
own iterators. Extension types implemented in C can implement a :c:member:`~PyTypeObject.tp_iter`
In 2.2, Python's :keyword:`for` statement no longer expects a sequence; it
expects something for which :func:`iter` will return an iterator. For backward
compatibility and convenience, an iterator is automatically constructed for
-sequences that don't implement :meth:`__iter__` or a :c:member:`~PyTypeObject.tp_iter` slot, so
+sequences that don't implement :meth:`!__iter__` or a :c:member:`~PyTypeObject.tp_iter` slot, so
``for i in [1,2,3]`` will still work. Wherever the Python interpreter loops
over a sequence, it's been changed to use the iterator protocol. This means you
can do things like this::
Oct 10
That's just the default behaviour. If you want to iterate over keys, values, or
-key/value pairs, you can explicitly call the :meth:`iterkeys`,
-:meth:`itervalues`, or :meth:`iteritems` methods to get an appropriate iterator.
+key/value pairs, you can explicitly call the :meth:`!iterkeys`,
+:meth:`!itervalues`, or :meth:`!iteritems` methods to get an appropriate iterator.
In a minor related change, the :keyword:`in` operator now works on dictionaries,
so ``key in dict`` is now equivalent to ``dict.has_key(key)``.
:keyword:`try`...\ :keyword:`finally` statement; read :pep:`255` for a full
explanation of the interaction between :keyword:`!yield` and exceptions.)
-Here's a sample usage of the :func:`generate_ints` generator::
+Here's a sample usage of the :func:`!generate_ints` generator::
>>> gen = generate_ints(3)
>>> gen
sentence := "Store it in the neighboring harbor"
if (i := find("or", sentence)) > 5 then write(i)
-In Icon the :func:`find` function returns the indexes at which the substring
+In Icon the :func:`!find` function returns the indexes at which the substring
"or" is found: 3, 23, 33. In the :keyword:`if` statement, ``i`` is first
assigned a value of 3, but 3 is less than 5, so the comparison fails, and Icon
retries it with the second value of 23. 23 is greater than 5, so the comparison
In recent versions, the distinction between regular integers, which are 32-bit
values on most machines, and long integers, which can be of arbitrary size, was
becoming an annoyance. For example, on platforms that support files larger than
-``2**32`` bytes, the :meth:`tell` method of file objects has to return a long
+``2**32`` bytes, the :meth:`!tell` method of file objects has to return a long
integer. However, there were various bits of Python that expected plain integers
and would raise an error if a long integer was provided instead. For example,
in Python 1.5, only regular integers could be used as a slice index, and
0.5. Without the ``__future__`` statement, ``/`` still means classic division.
The default meaning of ``/`` will not change until Python 3.0.
-* Classes can define methods called :meth:`__truediv__` and :meth:`__floordiv__`
+* Classes can define methods called :meth:`~object.__truediv__` and :meth:`~object.__floordiv__`
to overload the two division operators. At the C level, there are also slots in
the :c:type:`PyNumberMethods` structure so extension types can define the two
operators.
When built to use UCS-4 (a "wide Python"), the interpreter can natively handle
Unicode characters from U+000000 to U+110000, so the range of legal values for
-the :func:`unichr` function is expanded accordingly. Using an interpreter
+the :func:`!unichr` function is expanded accordingly. Using an interpreter
compiled to use UCS-2 (a "narrow Python"), values greater than 65535 will still
-cause :func:`unichr` to raise a :exc:`ValueError` exception. This is all
+cause :func:`!unichr` to raise a :exc:`ValueError` exception. This is all
described in :pep:`261`, "Support for 'wide' Unicode characters"; consult it for
further details.
Another change is simpler to explain. Since their introduction, Unicode strings
-have supported an :meth:`encode` method to convert the string to a selected
+have supported an :meth:`!encode` method to convert the string to a selected
encoding such as UTF-8 or Latin-1. A symmetric ``decode([*encoding*])``
method has been added to 8-bit strings (though not to Unicode strings) in 2.2.
-:meth:`decode` assumes that the string is in the specified encoding and decodes
+:meth:`!decode` assumes that the string is in the specified encoding and decodes
it, returning whatever is returned by the codec.
Using this new feature, codecs have been added for tasks not directly related to
>>> "sheesh".encode('rot-13')
'furrfu'
-To convert a class instance to Unicode, a :meth:`__unicode__` method can be
-defined by a class, analogous to :meth:`__str__`.
+To convert a class instance to Unicode, a :meth:`!__unicode__` method can be
+defined by a class, analogous to :meth:`!__str__`.
-:meth:`encode`, :meth:`decode`, and :meth:`__unicode__` were implemented by
+:meth:`!encode`, :meth:`!decode`, and :meth:`!__unicode__` were implemented by
Marc-André Lemburg. The changes to support using UCS-4 internally were
implemented by Fredrik Lundh and Martin von Löwis.
return g(value-1) + 1
...
-The function :func:`g` will always raise a :exc:`NameError` exception, because
+The function :func:`!g` will always raise a :exc:`NameError` exception, because
the binding of the name ``g`` isn't in either its local namespace or in the
module-level namespace. This isn't much of a problem in practice (how often do
you recursively define interior functions like this?), but this also made using
Line 4 containing the ``exec`` statement is a syntax error, since
``exec`` would define a new local variable named ``x`` whose value should
-be accessed by :func:`g`.
+be accessed by :func:`!g`.
This shouldn't be much of a limitation, since ``exec`` is rarely used in
most Python code (and when it is used, it's often a sign of a poor design
New and Improved Modules
========================
-* The :mod:`xmlrpclib` module was contributed to the standard library by Fredrik
+* The :mod:`!xmlrpclib` module was contributed to the standard library by Fredrik
Lundh, providing support for writing XML-RPC clients. XML-RPC is a simple
remote procedure call protocol built on top of HTTP and XML. For example, the
following snippet retrieves a list of RSS channels from the O'Reilly Network,
# 'description': 'A utility which converts HTML to XSL FO.',
# 'title': 'html2fo 0.3 (Default)'}, ... ]
- The :mod:`SimpleXMLRPCServer` module makes it easy to create straightforward
+ The :mod:`!SimpleXMLRPCServer` module makes it easy to create straightforward
XML-RPC servers. See http://xmlrpc.scripting.com/ for more information about XML-RPC.
* The new :mod:`hmac` module implements the HMAC algorithm described by
* Several functions that originally returned lengthy tuples now return
pseudo-sequences that still behave like tuples but also have mnemonic attributes such
- as memberst_mtime or :attr:`tm_year`. The enhanced functions include
- :func:`stat`, :func:`fstat`, :func:`statvfs`, and :func:`fstatvfs` in the
- :mod:`os` module, and :func:`localtime`, :func:`gmtime`, and :func:`strptime` in
+ as :attr:`!memberst_mtime` or :attr:`!tm_year`. The enhanced functions include
+ :func:`~os.stat`, :func:`~os.fstat`, :func:`~os.statvfs`, and :func:`~os.fstatvfs` in the
+ :mod:`os` module, and :func:`~time.localtime`, :func:`~time.gmtime`, and :func:`~time.strptime` in
the :mod:`time` module.
For example, to obtain a file's size using the old tuples, you'd end up writing
underlying the :mod:`re` module. For example, the :func:`re.sub` and
:func:`re.split` functions have been rewritten in C. Another contributed patch
speeds up certain Unicode character ranges by a factor of two, and a new
- :meth:`finditer` method that returns an iterator over all the non-overlapping
+ :meth:`~re.finditer` method that returns an iterator over all the non-overlapping
matches in a given string. (SRE is maintained by Fredrik Lundh. The
BIGCHARSET patch was contributed by Martin von Löwis.)
new extensions: the NAMESPACE extension defined in :rfc:`2342`, SORT, GETACL and
SETACL. (Contributed by Anthony Baxter and Michel Pelletier.)
-* The :mod:`rfc822` module's parsing of email addresses is now compliant with
+* The :mod:`!rfc822` module's parsing of email addresses is now compliant with
:rfc:`2822`, an update to :rfc:`822`. (The module's name is *not* going to be
changed to ``rfc2822``.) A new package, :mod:`email`, has also been added for
parsing and generating e-mail messages. (Contributed by Barry Warsaw, and
arising out of his work on Mailman.)
-* The :mod:`difflib` module now contains a new :class:`Differ` class for
+* The :mod:`difflib` module now contains a new :class:`!Differ` class for
producing human-readable lists of changes (a "delta") between two sequences of
- lines of text. There are also two generator functions, :func:`ndiff` and
- :func:`restore`, which respectively return a delta from two sequences, or one of
+ lines of text. There are also two generator functions, :func:`!ndiff` and
+ :func:`!restore`, which respectively return a delta from two sequences, or one of
the original sequences from a delta. (Grunt work contributed by David Goodger,
from ndiff.py code by Tim Peters who then did the generatorization.)
-* New constants :const:`ascii_letters`, :const:`ascii_lowercase`, and
- :const:`ascii_uppercase` were added to the :mod:`string` module. There were
- several modules in the standard library that used :const:`string.letters` to
+* New constants :const:`!ascii_letters`, :const:`!ascii_lowercase`, and
+ :const:`!ascii_uppercase` were added to the :mod:`string` module. There were
+ several modules in the standard library that used :const:`!string.letters` to
mean the ranges A-Za-z, but that assumption is incorrect when locales are in
- use, because :const:`string.letters` varies depending on the set of legal
+ use, because :const:`!string.letters` varies depending on the set of legal
characters defined by the current locale. The buggy modules have all been fixed
- to use :const:`ascii_letters` instead. (Reported by an unknown person; fixed by
+ to use :const:`!ascii_letters` instead. (Reported by an unknown person; fixed by
Fred L. Drake, Jr.)
* The :mod:`mimetypes` module now makes it easier to use alternative MIME-type
- databases by the addition of a :class:`MimeTypes` class, which takes a list of
+ databases by the addition of a :class:`~mimetypes.MimeTypes` class, which takes a list of
filenames to be parsed. (Contributed by Fred L. Drake, Jr.)
-* A :class:`Timer` class was added to the :mod:`threading` module that allows
+* A :class:`~threading.Timer` class was added to the :mod:`threading` module that allows
scheduling an activity to happen at some future time. (Contributed by Itamar
Shtull-Trauring.)
* Two new wrapper functions, :c:func:`PyOS_snprintf` and :c:func:`PyOS_vsnprintf`
were added to provide cross-platform implementations for the relatively new
:c:func:`snprintf` and :c:func:`vsnprintf` C lib APIs. In contrast to the standard
- :c:func:`sprintf` and :c:func:`vsprintf` functions, the Python versions check the
+ :c:func:`sprintf` and :c:func:`!vsprintf` functions, the Python versions check the
bounds of the buffer used to protect against buffer overruns. (Contributed by
M.-A. Lemburg.)
* The :file:`Tools/scripts/ftpmirror.py` script now parses a :file:`.netrc`
file, if you have one. (Contributed by Mike Romberg.)
-* Some features of the object returned by the :func:`xrange` function are now
+* Some features of the object returned by the :func:`!xrange` function are now
deprecated, and trigger warnings when they're accessed; they'll disappear in
- Python 2.3. :class:`xrange` objects tried to pretend they were full sequence
+ Python 2.3. :class:`!xrange` objects tried to pretend they were full sequence
types by supporting slicing, sequence multiplication, and the :keyword:`in`
operator, but these features were rarely used and therefore buggy. The
- :meth:`tolist` method and the :attr:`start`, :attr:`stop`, and :attr:`step`
+ :meth:`!tolist` method and the :attr:`!start`, :attr:`!stop`, and :attr:`!step`
attributes are also being deprecated. At the C level, the fourth argument to
the :c:func:`!PyRange_New` function, ``repeat``, has also been deprecated.
projects / thirdparty / Python / cpython.git / commitdiff
