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From: Terry Reedy <tjreedy@udel.edu>
Newsgroups: comp.lang.python
Subject: Re: Which Python editor has this feature?
Date: Wed, 13 Jan 2016 04:05:18 -0500
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On 1/12/2016 5:18 AM, Chris Angelico wrote:
> On Tue, Jan 12, 2016 at 7:27 PM, Terry Reedy <tjreedy@udel.edu> wrote:

>> Can psycopg2 be installed with pip?  There is an issue (#23551) to mak=
e a
>> pip GUI and make it accessible from IDLE.  We need someone with both p=
ip and
>> tkinter knowledge to either design and write it or mentor a GSOC stude=
nt to
>> do so.  One written, I would add an IDLE menu item to run it, in a sep=
arate
>> process, just as done now with turtledemo.
>
> Yes, invisible smiley... but with a hint of truth too. Obviously
> installing PostgreSQL itself is outside the scope of IDLE, but
> psycopg2 is indeed pip-installable... except that it isn't always, on
> Windows, because wheels aren't available for all versions. (There's no
> Python 3.5 wheel yet; at least, I can't see one on PyPI.)

Maybe someone should give them a prod.  It has been 4 months.
http://www.lfd.uci.edu/~gohlke/pythonlibs/
only has psycopg, for 2.6.

 > So what I'm
> really looking for isn't an IDLE feature but a Python packaging
> feature - some people have talked about setting up build farms that
> can produce wheels for people.

Building binaries is a rather different issue, certainly on Windows.

> Hmm. I just tried this, and actually, there's some possibly
> low-hanging fruit. (Tested on Python 3.4.3 as 3.5 can't install
> psycopg2 anyway.)
>
>>>> import pip; pip.main(["install","psycopg2"])

https://bugs.python.org/issue23551
has my report of experimenting with directly using pip.main.  The main=20
issue I ran into is that pip creates a cache of 'currently installed=20
packages' the first time it needs it and never again during the same=20
process.  In other words, pip.main is called exactly once when pip is=20
run from the command line.  Another command from the command line starts =

a new process, which makes a new cache.  So calling main() repeatedly=20
may fail due to a stale cache.  However, the need to refresh it is=20
predictable, so reloading the module may work.

> This produces a rather messy display, because pip.main seems to assume
> that writing carriage returns to the console will result in the
> display nicely overwriting (producing a moving progress bar as the
> file gets downloaded). If IDLE can't handle carriage returns as such,
> an easy fix would be to simply display them as complete lines; it
> would be more verbose than the normal console behaviour, but not as
> ugly.

Currently, Idle sends user code output to the tk Text widget as is,=20
except for colorizing.  There was an issue about changing this, but it=20
was closed, at least for the time being, as Python allows print to send=20
output to any file and does not require than stdout be connected to a=20
'console', and anyway there is no standard for console behavior.

A gui program that runs pip and displays its output would generally=20
parse output for display in differnet widgets.
>
> A couple of other random thoughts from this experiment.
>
> * Going to python.org and pointing the mouse at the download link got
> me 3.5.1 32-bit. This is on Google Chrome on a Windows 7 64-bit VM.
> * Instead of pip.main(["install","psycopg2"]), I'd like to be able to
> say pip.install("psycopg2"). In fact, I might take that to the pip
> folks as a suggestion.

> * The performance difference between "import pip" on 3.4.3 and 3.5.1
> was dramatic! I don't know whether it's CPython that's been sped up or
> pip itself, but it's awesome!

Try with 3.4.4, as I believe its installer should also update to the=20
most recent pip version.

> There's some kind of issue between pip and Idle that means that
> installing a non-wheel blows up with an exception:
>
>
> Traceback (most recent call last):
>    File "C:\Users\Rosuav\AppData\Local\Programs\Python\Python35-32\lib\=
site-packages\pip\basecommand.py",
> ...
>      return s.decode(sys.__stdout__.encoding)
> AttributeError: 'NoneType' object has no attribute 'encoding'

Assuming that sys.__sydout__ is not None is a bug on pip's part.=20
Perhaps you could report it to it list or tracker, and point Donald and=20
whoever to https://docs.python.org/3/library/sys.html#sys.__stdin__

"Note

Under some conditions stdin, stdout and stderr as well as the original=20
values __stdin__, __stdout__ and __stderr__ can be None. It is usually=20
the case for Windows GUI apps that aren=E2=80=99t connected to a console =
and=20
Python apps started with pythonw."

IDLE is a GUI app that on Windows is started with pythonw.exe.  More=20
relevant, user code is executed in a windowless pythonw process.  The=20
same problem should occur with any IDE that executes user code in a=20
pythonw process.

A GUI program could work around the bug by setting sys.__stdin__ to an=20
object with a .encoding attribute.  I checked that this can be done.

> Maybe calling pip.main just isn't a supported thing, but it'd be nice
> if there were _some_ way to do this, even without a fancy GUI.

Calling is once during a process is supported, or supposed to be.
If you ran, at the console,
   > pythonw.exe -c "import pip; pip.main(['install','psycopg2'])"
the same failure would happen.  However, the only indication of failure, =

before you checked site-packages and found no psycopg2, would be the=20
quick return to the console prompt.

> How much of this is worth doing anything about, and how much is "hey,
> you're hacking around calling a command-line tool from inside a GUI,
> and stuff ain't a'gonna work right"?

On the issue linked above, Donald Stuffit, a (the?) pip maintainer, said =

that he wanted there to be a pip Gui, even though he was unlikely to=20
write it himself.  We have identified 3 problems; I believe all can be=20
worked around.  I added your two and the workarounds to the issue.

--=20
Terry Jan Reedy