[New-bugs-announce] [issue4968] Clarify inspect.is<callable> method docs

Terry J. Reedy report at bugs.python.org
Sat Jan 17 04:26:09 CET 2009

New submission from Terry J. Reedy <tjreedy at udel.edu>:

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."

assignee: georg.brandl
components: Documentation
messages: 79999
nosy: georg.brandl, tjreedy
severity: normal
status: open
title: Clarify inspect.is<callable> method docs
versions: Python 3.0, Python 3.1

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