Issue 4517: improve getattribute documentation (original) (raw)

Created on 2008-12-04 04:34 by LambertDW, last changed 2022-04-11 14:56 by admin. This issue is now closed.

Messages (5)
msg76867 - (view)	Author: David W. Lambert (LambertDW)	Date: 2008-12-04 04:34
http://docs.python.org/dev/3.0/reference/datamodel.html#special-lookup (After fixing the link to http://docs.python.org/3.0 at http://www.python.org/doc/ (and likewise the http://docs.python.org/whatsnew/3.0.html link.)... The comment that __getattribute__ is "Called unconditionally to implement attribute accesses for instances of the class" gave me hope that some combination of "meta" "super" and "sub" might let me access __getattribute__ for expression eval('obj + another_object') despite the special notes. I realize now the truth is that "__getattribute__ is NEVER accessible in pure python code when the code uses the syntax of a unary or binary operator such as a+b, ~a, len(a)." See most of the functions in this manual section. Also name hash, which doesn't find much explicit use but could well be the most used python functionality. Find a smooth way to replace my NEVER since code can obviously access __getattribute__ from the special function. Thank you, and great work!
msg76868 - (view)	Author: David W. Lambert (LambertDW)	Date: 2008-12-04 04:38
>>> class c: ... def __getattribute__(self,*args): ... print('getattribute chimes in') ... >>> c()+3 Traceback (most recent call last): File "", line 1, in TypeError: unsupported operand type(s) for +: 'c' and 'int'
msg77021 - (view)	Author: Georg Brandl (georg.brandl) *	Date: 2008-12-05 14:45
Isn't what you refer to covered by this paragraph and the following example: "In addition to bypassing any instance attributes in the interest of correctness, implicit special method lookup may also bypass the __getattribute__() method even of the object’s metaclass:"?
msg77029 - (view)	Author: David W. Lambert (LambertDW)	Date: 2008-12-05 15:21
Yes to . However! I'll pin the difficulty specifically to the word "may". This cost me a lot of time. 1) Please change the phrasing you quoted to "... implicit special method lookup bypasses the __getattribute__() method even of the object’s metaclass:" 2) Please insert into the glossary a definition of "implicit special method lookup" that addresses the grammar or syntax that causes it considering monad and dyad use. Thank you.
msg77030 - (view)	Author: Georg Brandl (georg.brandl) *	Date: 2008-12-05 15:29
I've changed "may bypass" to "generally bypasses". It doesn't happen for all methods, but that's an implementation detail. I've also added a glossary entry "special method" in r67579.