Separate out the type/class-related news and reword some items.
Add news items about comparisons, repr(), __class__ assignment.
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Guido van Rossum
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102
Misc/NEWS
102
Misc/NEWS
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@ -1,7 +1,19 @@
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What's New in Python 2.2a4?
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===========================
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Core
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Type/class unification and new-style classes
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- pydoc and inspect are now aware of new-style classes;
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e.g. help(list) at the interactive prompt now shows proper
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documentation for all operations on list objects.
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- Applications using Jim Fulton's ExtensionClass module can now safely
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be used with Python 2.2. In particular, Zope 2.4.1 now works with
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Python 2.2 (as well as with Python 2.1.1). The Demo/metaclass
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examples also work again. It is hoped that Gtk and Boost also work
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with 2.2a4 and beyond. (If you can confirm this, please write
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webmaster@python.org; if there are still problems, please open a bug
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report on SourceForge.)
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- property() now takes 4 keyword arguments: fget, fset, fdel and doc.
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These map to readonly attributes 'fget', 'fset', 'fdel', and '__doc__'
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@ -9,6 +21,56 @@ Core
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discoverable from Python in 2.2a3. __doc__ is new, and allows to
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associate a docstring with a property.
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- Comparison overloading is now more completely implemented. For
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example, a str subclass instance can properly be compared to a str
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instance, and it can properly overload comparison. Ditto for most
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other built-in object types.
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- The repr() of new-style classes has changed; instead of <type
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'M.Foo'> a new-style class is now rendered as <class 'M.Foo'>,
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*except* for built-in types, which are still rendered as <type
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'Foo'> (to avoid upsetting existing code that might parse or
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otherwise rely on repr() of certain type objects).
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- The repr() of new-style objects is now always <Foo object at XXX>;
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previously, it was sometimes <Foo instance at XXX>.
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- For new-style classes, what was previously called __getattr__ is now
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called __getattribute__. This method, if defined, is called for
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*every* attribute access. A new __getattr__ hook mor similar to the
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one in classic classes is defined which is called only if regular
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attribute access raises AttributeError; to catch *all* attribute
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access, you can use __getattribute__ (for new-style classes). If
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both are defined, __getattribute__ is called first, and if it raises
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AttributeError, __getattr__ is called.
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- The __class__ attribute of new-style objects can be assigned to.
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The new class must have the same C-level object layout as the old
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class.
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- The builtin file type can be subclassed now. In the usual pattern,
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"file" is the name of the builtin type, and file() is a new builtin
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constructor, with the same signature as the builtin open() function.
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file() is now the preferred way to open a file.
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- Previously, __new__ would only see sequential arguments passed to
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the type in a constructor call; __init__ would see both sequential
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and keyword arguments. This made no sense whatsoever any more, so
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now both __new__ and __init__ see all arguments.
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- Previously, hash() applied to an instance of a subclass of str or
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unicode always returned 0. This has been repaired.
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- Previously, an operation on an instance of a subclass of an
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immutable type (int, long, float, complex, tuple, str, unicode),
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where the subtype didn't override the operation (and so the
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operation was handled by the builtin type), could return that
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instance instead a value of the base type. For example, if s was of
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a str sublass type, s[:] returned s as-is. Now it returns a str
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with the same value as s.
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Core
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- file.writelines() now accepts any iterable object producing strings.
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- PyUnicode_FromEncodedObject() now works very much like
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@ -22,40 +84,6 @@ Core
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of a print statement must support Unicode objects, i.e. they must
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at least convert them into ASCII strings.
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- The builtin file type can be subclassed now. In the usual pattern,
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"file" is the name of the builtin type, and file() is a new builtin
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constructor, with the same signature as the builtin open() function.
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file() is now the preferred way to open a file.
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- In 2.2a3, *for new-style classes only*, __getattr__ was called for
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every attribute access. This was confusing because it differed
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significantly from the behavior of classic classes, where it was
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only called for missing attributes. Now, __getattr__ is called only
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if regular attribute access raises AttributeError; to catch *all*
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attribute access, *for new-style classes only*, you can use
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__getattribute__. If both are defined, __getattribute__ is called
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first, and if it raises AttributeError, __getattr__ is called.
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- In 2.2a3, __new__ would only see sequential arguments passed to the
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type in a constructor call; __init__ would see both sequential and
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keyword arguments. This made no sense whatsoever any more, so
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now both __new__ and __init__ see all arguments.
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- In 2.2a3, hash() applied to an instance of a subclass of str or unicode
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always returned 0. This has been repaired.
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- In 2.2a3, an operation on an instance of a subclass of an immutable type
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(int, long, float, complex, tuple, str, unicode), where the subtype
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didn't override the operation (and so the operation was handled by the
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builtin type), could return that instance instead a value of the base
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type. For example, if s was of a str sublass type, s[:] returned s
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as-is. Now it returns a str with the same value as s.
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- Applications using Jim Fulton's ExtensionClass module can now safely
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be used with Python 2.2. In particular, Zope 2.4.1 now works with
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Python 2.2 (as well as with Python 2.1.1). The Demo/metaclass
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examples also work again.
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- Thread scheduling on Solaris should be improved; it is no longer
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necessary to insert a small sleep at the start of a thread in order
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to let other runnable threads be scheduled.
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@ -102,10 +130,6 @@ Library
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Tool to a standard library package. (Tools/compiler still exists as
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a sample driver.)
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- pydoc and inspect are now aware of new-style classes;
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e.g. help(list) at the interactive prompt now shows proper
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documentation for all operations on list objects.
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Tools
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Build
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