Re: [matplotlib-devel] matplotlib 0.63 examples under pylab

[Fernando P. <Fer...@co...>]

John Hunter schrieb:
>>>>>>"Fernando" =3D=3D Fernando Perez <Fer...@co...> writ=
es:
>=20
>=20
>     Fernando> I think we're doing pretty good, except that people can
>     Fernando> always kill themselves by running true WX/GTK apps via
>     Fernando> @run.  IPython is really not made for this, it can only
>     Fernando> handle gracefully show() calls from pure matplotlib
>     Fernando> scripts, not full-blown GUI apps.  But I think we have a
>     Fernando> very reasonable environment at this point for most usage
>     Fernando> cases.
>=20
> It's looks like about 90% of your problems result from trying to cross
> GUI backends within IPython.  Is this fair to say?

Well, not quite.  As I mentioned, I put in a matplotlib.use() wrapper whi=
ch=20
traps invalid switches, so it's not a problem if a use() call is made.  C=
ould=20
you add such a call to this one please? :

// OK with GTKAgg backend. It needs a use('GTKAgg') call to be safe for o=
ther
backends.
run dynamic_image_gtkagg.py


It's only when native GUI examples are run that things crash badly.  Note=
 that=20
some of the segfaults occur from plain python:

// these are OK with gtkagg, but they segfault wxagg.  The segfault happe=
ns
from a normal command line as well (no ipython).

run system_monitor.py
run dynamic_demo.py

And I also have these:
// these two run but segfault on exit under ipython.  They run OK from a =
cmd line.
run dynamic_demo_wx.py
run dynamic_image_wxagg.py

I suspect these two are messing something up badly enough that if python =
quits=20
right away, you don't see the problem, but since ipython continues to run=
 the=20
interpreter, the problem appears.  Since these are segfaults, I'm very mu=
ch=20
willing to blame the wx code in there, and not ipython (which is 100% pur=
e,=20
unpolluted python :)

> As far as I'm concerned I don't have a problem with these cases.
> Caveat emptor -- the user should be forewarned and expect disaster if
> they try and run GUI specific examples from ipython.  Perhaps you
> should say pylab only supports pure matlab interface matplotlib at
> this point.
>=20
>>From your end I see why it's a concern - you don't want any run
> command to break or freeze ipython.  If you have any ideas on what we
> should do I'll be happy to help on the matplotlib end, but I don't
> have any off the top of my head.

Yes, this is the real nasty.  If you think that the ipython+matplotlib=20
combination is going to be a common one in the future for scientists, it =
may=20
be worth protecting the examples against disaster (given they tend to be =
what=20
people run to first).  If you are willing to pay the price of 12 lines of=
 code=20
per example, you could put this snippet at the beginning of _every_ embed=
ded=20
example:

# Detect if we are inside IPython and bail if so.  Threading problems
# make it very difficult to safely run full GTK/WX apps inside IPython.
try:
     __IPYTHON__
     msg =3D ("This script can NOT be run inside IPython.\n\n"
            "It embeds matplotlib into a complete GUI application, and\n"
            "for a number of reasons this is (and probably will remain)\n=
"
            "unsupported from inside IPython.\n\n"
            "You can run it from the command line as a regular python scr=
ipt.\n")
     raise RuntimeError,msg
except NameError:
     pass

This will make sure that users get a meaningful error message inside ipyt=
hon=20
instead of a bizarre lockup or segfault.


> I'll comment on some of the non cross-GUI problems below....
>=20
>     Fernando> // These don't run with LANG=3D=3Dde_DE.UTF-8, but are OK
>     Fernando> with en_US.UTF-8 run date_demo_convert.py run
>     Fernando> date_demo1.py run date_demo2.py run date_demo_rrule.py
>     Fernando> run finance_demo.py
>=20
> Do they run from the shell with LANG=3D=3Dde_DE.UTF-8?  Any idea what i=
s
> going wrong?

Yes, the problem has nothing to do with ipython, it also happens with pla=
in=20
python.  Note that the broken ones are:

// These don't run with LANG=3D=3Dde_DE.UTF-8, but are OK with en_US.UTF-=
8
run date_demo1.py
run date_demo2.py
run finance_demo.py

I think my original list had more by mistake.  Here's a traceback (form=20
ipython, so you get better details):

In [5]: run date_demo1.py
-------------------------------------------------------------------------=
--
ValueError                                Traceback (most recent call las=
t)

/home/fperez/code/python/pylab/examples/date_demo1.py
      26 yearsFmt =3D DateFormatter('%Y')
      27
---> 28 quotes =3D quotes_historical_yahoo(
      29     'INTC', date1, date2)
      30 if not quotes:

/usr/local/lib/python2.3/site-packages/matplotlib/finance.py in=20
quotes_historical_yahoo(ticker, date1, date2)
      61         if len(vals)!=3D7: continue
      62         datestr =3D vals[0]
---> 63         dt =3D datetime.date(*time.strptime(datestr, '%d-%b-%y')[=
:3])
      64         d =3D date2num(dt)
      65         open, high, low, close =3D  [float(val) for val in vals[=
1:5]]

/usr/src/build/394694-i386/install/usr/lib/python2.3/_strptime.py in=20
strptime(data_string, format)
     422     found =3D format_regex.match(data_string)
     423     if not found:
--> 424         raise ValueError("time data did not match format:  data=3D=
%s=20
fmt=3D%s" %
     425                          (data_string, format))
     426     if len(data_string) !=3D found.end():

ValueError: time data did not match format:  data=3D31-Mar-04  fmt=3D%d-%=
b-%y
WARNING: Failure executing file: <date_demo1.py>

The problem is that under different locales, dates come out formatted=20
differently.  You seem to have hardcoded format expectations which break =
in=20
the face of non-US locales.

>     Fernando> run print_stdout.py
>=20
> This is an example script to show how to print png to stdout from agg.
> Perhaps this fails because ipython doesn't really expect a png coming
> in from stdout?  The header of that file states

Well, running it again I'm getting this:

Exception in thread Thread-1:
Traceback (most recent call last):
   File "/usr/src/build/394694-i386/install/usr/lib/python2.3/threading.p=
y",=20
line 436, in __bootstrap
     self.run()
   File "/home/fperez/code/python/IPython/Shell.py", line 527, in run
     self.IP.mainloop()
   File "/home/fperez/code/python/IPython/iplib.py", line 948, in mainloo=
p
     self.interact(banner)
   File "/home/fperez/code/python/IPython/iplib.py", line 1036, in intera=
ct
     line =3D self.raw_input(prompt)
   File "/home/fperez/code/python/IPython/iplib.py", line 1263, in raw_in=
put
     return self.prefilter(raw_input(prompt),
IOError: [Errno 9] Ung=FCltiger Dateideskriptor

Pehaps you could add (if you decide that you like that idea) the __IPYTHO=
N__=20
trap code to this as well, so that all examples are made ipython-friendly=
.  In=20
this one, the message could additionally show this:

   print png to standard out
   usage: python print_stdout.py > somefile.png

so users know what to do straight away.

> Thanks for the detailed notes.

No prob.  I'm a big believer that good examples are what helps most new u=
sers,=20
so I'm trying to make sure that out-of-the-box, things run as smoothly as=
=20
possible for all those scientists who are just dying to start using matpl=
otlib=20
  with ipython :)

Best,

f