Bug with help (was Re: Getting a list of all modules)

[Terry Reedy]

On 8/2/2014 8:13 AM, Robert Kern wrote:
> On 2014-08-02 09:33, Heinz Schmitz wrote:
>> Akira Li wrote:
>>
>>>>> Look at how `help('modules')` is implemented. Though it crashes on my
>>>>> system.
>>
>>>> Have you reported this at bugs.python.org or is there already an issue
>>>> for the problem that you see?
>>
>>> It is this issue for python2.7:
>>> https://bugs.launchpad.net/ubuntu/+source/python2.7/+bug/896836
>>>
>>> python3 doesn't crash with currently installed packages.
>>
>> Python 2.7 on Windows XP Sp2 doesn't crash with this. So it seems to
>> be a python<->OS-problem.

It is a local system problem.

> Well, it's just that `help('modules')` imports every module in the
> calling process (at least in Python 2.7; I haven't checked Python 3).
> Some extension modules conflict with each other and cause a crash when
> both are imported together. It's possible that you just don't have such
> modules installed. While the proximate cause of the crash is in the 3rd
> party modules, Python could (and maybe Python 3 does) import each module
> in a separate subprocess and collect the information that way.

That would slow down help('modules') much more.  The suggestion in
http://bugs.python.org/issue12902
"help("modules") executes module code"
is that help() should instead parse the module to get the docstring.

-- 
Terry Jan Reedy