[Tutor] Total newbie question

[MR ZenWiz]

On Tue, Jan 3, 2017 at 5:15 PM, Cameron Simpson <cs at zip.com.au> wrote:
> On 03Jan2017 17:07, Peter Otten <__peter__ at web.de> wrote:
>>
>> Cameron Simpson wrote:
>>>
>>> On 02Jan2017 17:21, MR ZenWiz <mrzenwiz at gmail.com> wrote:
>>>>
>>>> I'm trying to install python 4.6 on my Xubuntu 16.04 desktop, [...]
>>>> INFO: Can't locate Tcl/Tk libs and/or headers
>>>
>>> You lack the tk development libraries and/or headers. Try (as root):
>>>   apt-get install tk-dev
>
> [...]
>>>
>>> You need a bunch of other devleopment libraries too. [...]
>>
>>
>> A nice shortcut for this is to install the build dependencies of the
>> Python
>> 3 used by your distribution:
>>
>> $ sudo apt-get build-dep python3.x
>>
>> Replace x with the actual minor version present on your system.
>
>
> I Did Not Know This!
>
> Yes, that sounds far more reliable than my guess-the-names approach.
>
> Thank you,
>

If that had worked, I'd be quite pleased, but as I posted earlier,
apgt-get claims not to know what to do with that.

I tried deleting all the ~/.local/python3* files and also all python
files in /etc and /usr, then reinstalled all the (previously) system
installed version via synaptic, and python3.5 seems to work as a
command, but idle3 does not:

admar at marbase:~ $ which idle3
/usr/local/bin/idle3
admar at marbase:~ $ which idle3.5
/usr/local/bin/idle3.5
admar at marbase:~ $ which python3
/usr/bin/python3
admar at marbase:~ $ which python3.5
/usr/bin/python3.5
admar at marbase:~ $ idle3
bash: /usr/local/bin/idle3: /usr/local/bin/python3.5: bad interpreter:
No such file or directory
admar at marbase:~ $ idle3.5
bash: /usr/local/bin/idle3.5: /usr/local/bin/python3.5: bad
interpreter: No such file or directory

It appears that while python is installed in /usr/bin, idle is in
/usr/local/bin and expects the python interpreter to be also under
/usr/local, which does not seem to be the default.

I created a symlink 'ln -s /usr/bin/python3.5
/usr/local/bin/python3.5' and now idle comes up.

While this works, it is not at all intuitive (and I haven't exercised
it to see how robust this is).

What would make the idle want something that isn't there without such hackery?

Thanks.
MR