Bugs item #1156412, was opened at 2005-03-03 22:00 Message generated for change (Comment added) made by gward You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1156412&group_id=5470
Category: Documentation Group: Python 2.5 Status: Open Resolution: None Priority: 5 Submitted By: Steven Bethard (bediviere) Assigned to: Nobody/Anonymous (nobody) Summary: add documentation for __new__ Initial Comment: 3.3.1 Basic customization does not document __new__. Proposed addition: __new__(cls[, ...]) Called to create a new instance of the class. __new__ is a staticmethod (special-cased so you need not declare it as such) that takes the class to be created as the first argument. The remaining arguments are those passed to the class constructor expression. The return value of __new__ should be the new object instance. Typical usage is to create a new instance of the class by invoking the superclass's __new__ method using "super(BaseClass, cls).__new__([...])" with appropriate arguments, modifying the returned instance if necessary, and then returning it. If the returned value is an instance of "cls" (the first argument to __new__), its __init__ will be invoked. Note that you need not return an instance of "cls", but if you don't, the new instance's __init__ method will not be invoked. The __new__ staticmethod is intended mainly to allow modification of immutable types like int, long, float, str and tuple. ---------------------------------------------------------------------- >Comment By: Greg Ward (gward) Date: 2005-03-05 11:11 Message: Logged In: YES user_id=14422 I think that last paragraph can be written even more concisely: "The __new__ staticmethod is intended mainly to allow subclasses of immutable types (like int, str, or tuple) to customize instance creation." Also, the usual convention when talking about methods and functions is to write "__new__()", not "__new__". At least that's how the 2.3.3 language ref which I have on my PC looks. Finally, this bug is in the "Python 2.5" group -- surely there's no harm in checking this in to the 2.4 docs and merging forward? ---------------------------------------------------------------------- Comment By: Nick Coghlan (ncoghlan) Date: 2005-03-04 23:02 Message: Logged In: YES user_id=1038590 Close, but the phrasing's a bit awkward. Getting rid of the commas seems to fix that: "The __new__ staticmethod is intended mainly to allow you to customize instance creation in a subclass of an immutable type (like int, long, float, complex, str, unicode, or tuple)." ---------------------------------------------------------------------- Comment By: Steven Bethard (bediviere) Date: 2005-03-04 15:19 Message: Logged In: YES user_id=945502 Good point. How about: "The __new__ staticmethod is intended mainly to allow you, in a subclass of an immutable type (like int, long, float, complex, str, unicode, or tuple), to customize instance creation." ---------------------------------------------------------------------- Comment By: Oren Tirosh (orenti) Date: 2005-03-04 13:05 Message: Logged In: YES user_id=562624 "The __new__ staticmethod is intended mainly to allow modification of immutable types like int, long, float, str and tuple." You might like to rephrase that. It gives the impression that __new__ somehow makes it possible to modify the value of an immutable object. In fact, it only allows customized creation of new instances. ---------------------------------------------------------------------- Comment By: Steven Bethard (bediviere) Date: 2005-03-04 11:11 Message: Logged In: YES user_id=945502 Yup, type_call in typeobject.c special-cases this behavior. See also http://sourceforge.net/tracker/?func=detail&aid=1123716&group_id=5470&atid=105470 ---------------------------------------------------------------------- Comment By: Nick Coghlan (ncoghlan) Date: 2005-03-04 10:53 Message: Logged In: YES user_id=1038590 Looks reasonable to me - but does CPython actually currently follow those rules regarding when __init__ is and isn't invoked? ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1156412&group_id=5470 _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
