Clarify inspect.is<callable> method docs

[terryjreedy]

BPO	4968
Nosy	@birkenfeld, @terryjreedy

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2010-10-15.16:53:38.086>
created_at = <Date 2009-01-17.03:26:08.466>
labels = ['docs']
title = 'Clarify inspect.is<callable> method docs'
updated_at = <Date 2010-10-15.16:53:38.085>
user = 'https://github.com/terryjreedy'

bugs.python.org fields:

activity = <Date 2010-10-15.16:53:38.085>
actor = 'georg.brandl'
assignee = 'docs@python'
closed = True
closed_date = <Date 2010-10-15.16:53:38.086>
closer = 'georg.brandl'
components = ['Documentation']
creation = <Date 2009-01-17.03:26:08.466>
creator = 'terry.reedy'
dependencies = []
files = []
hgrepos = []
issue_num = 4968
keywords = []
message_count = 4.0
messages = ['79999', '109272', '109968', '118802']
nosy_count = 4.0
nosy_names = ['georg.brandl', 'terry.reedy', 'docs@python', 'BreamoreBoy']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue4968'
versions = ['Python 3.1', 'Python 3.2']

[terryjreedy]

inspect module in 3.0

.isclass: says "Return true if the object is a class." Since the issue
of builtin versus Python coded is involved in all the other methods
below, I would expand this to
"Return true if the object is a class, whether built-in or Python-coded."
to emphasize that this is not an issue for this one.

.isfunction: current "Return true if the object is a Python function or
unnamed (lambda) function." falsely implies that there is such a thing
as 'unnamed (lambda) function; different from 'Python function'. By
test, it just returns True for 'function' objects. Suggestion:

"Return true for Python-coded functions, including unbound Python-coded
methods." or possibly
"Return true for functions created by def statements and lambda
expressions, including unbound Python-coded methods.

.ismethod: "Return true if the object is a method." should be specified
to something like
"Return true if the object is a bound method written in Python."

.isbuiltin: says "Return true if the object is a built-in function."
but actually tests for membership in class 'builtin_function_or_method'.
I believe that truth is
"Return true if the object is a built-in function (but not a class) or a
bound built-in non-special method."
It is True, for instance, for [].append but not [].__hash__. I am
assuming that this behavior is intended and not a bug.

.ismethoddescriptor: "Return true if the object is a method descriptor,
but not if ismethod() or isclass() or isfunction() are true." begs the
question of what a method descriptor is. I believe the following is
both true and clearer.
"Return true if the object is a built-in method and isbuiltin() is false.

I would follow with
"The methods isclass, isfunction, ismethod, isbuiltin, and
ismethoddescriptor are mutually exclusive."
I believe the following is true, and could be added also.
"Exact one is true for any instance of a built-in callable class."

[BreamoreBoy]

Has this issue simply slipped under the radar?

[birkenfeld]

No, I've just had no time to review the suggested changes.

[birkenfeld]

Committed suggestions with a few changes in r85541.