[docs] [issue17279] Document which named built-in classes can be subclassed

[Terry J. Reedy]

New submission from Terry J. Reedy:

More than once, people have noted on python-list that not all built-in classes can be subclassed and that there seems to be no way to find out which, other than to try each. (Today, Daniel Urban pointed out the CPython-specific 'xx.__flags__ & (1 << 10)'.) If the specifics are a Python feature, rather than CPython specific, I think they should be given in the doc.

There is a recent issue, which I cannot find, about re-organizing the Library built-in functions chapter by groups. If this is done, it would be easy to add, in the introduction to built-in classes, a list of which of the named classes can or cannot be subclassed (whichever list is shorter) and note that those not in builtins cannot be.)

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assignee: docs at python
components: Documentation
messages: 182703
nosy: docs at python, terry.reedy
priority: normal
severity: normal
stage: needs patch
status: open
title: Document which named built-in classes can be subclassed
type: enhancement
versions: Python 2.7, Python 3.3, Python 3.4

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue17279>
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