matplotlib-devel

[matplotlib-devel] Error in import matplotlib.pyplot using Python/C API

[Filipe S. <ma...@fi...>]

Hello,

First, thanks for this great library.

My name is Filipe Saraiva, I am developing a python backend for Cantor, 
the KDE mathematical software. More infos can be read in 
http://blog.filipesaraiva.info/?tag=gsoc2013-python-backend (in 
portuguese and english).

Currently I have a problem when I try import pyplot in Cantor. I am 
using Python 2.7.5 and matplotlib 1.3.0. The error is below:

import matplotlib.pyplot as plt
Traceback (most recent call last):
   File "<string>", line 1, in <module>
   File "/usr/lib64/python2.7/site-packages/matplotlib/pyplot.py", line 
98, in <module>
     _backend_mod, new_figure_manager, draw_if_interactive, _show = 
pylab_setup()
   File 
"/usr/lib64/python2.7/site-packages/matplotlib/backends/__init__.py", 
line 25, in pylab_setup
     globals(),locals(),[backend_name])
   File 
"/usr/lib64/python2.7/site-packages/matplotlib/backends/backend_qt4agg.py", 
line 19, in <module>
     _decref = ctypes.pythonapi.Py_DecRef
   File "/usr/lib64/python2.7/ctypes/__init__.py", line 378, in __getattr__
     func = self.__getitem__(name)
   File "/usr/lib64/python2.7/ctypes/__init__.py", line 383, in __getitem__
     func = self._FuncPtr((name_or_ordinal, self))
AttributeError: kde/bin/cantor: undefined symbol: Py_DecRef

Well, anyone have any idea about how can I fix it?

Thank you,


-- Filipe Saraiva http://filipesaraiva.info/

Re: [matplotlib-devel] Error in import matplotlib.pyplot using Python/C API

[Benjamin R. <ben...@ou...>]

On Mon, Sep 2, 2013 at 12:27 AM, Filipe Saraiva <ma...@fi...>wrote:

>  Hello,
>
> First, thanks for this great library.
>
> My name is Filipe Saraiva, I am developing a python backend for Cantor,
> the KDE mathematical software. More infos can be read in
> http://blog.filipesaraiva.info/?tag=gsoc2013-python-backend (in
> portuguese and english).
>
> Currently I have a problem when I try import pyplot in Cantor. I am using
> Python 2.7.5 and matplotlib 1.3.0. The error is below:
>
> import matplotlib.pyplot as plt
> Traceback (most recent call last):
>   File "<string>", line 1, in <module>
>   File "/usr/lib64/python2.7/site-packages/matplotlib/pyplot.py", line 98,
> in <module>
>     _backend_mod, new_figure_manager, draw_if_interactive, _show =
> pylab_setup()
>   File
> "/usr/lib64/python2.7/site-packages/matplotlib/backends/__init__.py", line
> 25, in pylab_setup
>     globals(),locals(),[backend_name])
>   File
> "/usr/lib64/python2.7/site-packages/matplotlib/backends/backend_qt4agg.py",
> line 19, in <module>
>     _decref = ctypes.pythonapi.Py_DecRef
>   File "/usr/lib64/python2.7/ctypes/__init__.py", line 378, in __getattr__
>     func = self.__getitem__(name)
>   File "/usr/lib64/python2.7/ctypes/__init__.py", line 383, in __getitem__
>     func = self._FuncPtr((name_or_ordinal, self))
> AttributeError: kde/bin/cantor: undefined symbol: Py_DecRef
>
> Well, anyone have any idea about how can I fix it?
>
> Thank you,
>
>
My only guess is that there is some sort of linking/build error. Perhaps
the python-qt4 library was built and linked against a different python on
your system?

Cheers!
Ben Root

Re: [matplotlib-devel] Error in import matplotlib.pyplot using Python/C API

[Filipe S. <ma...@fi...>]

Em Ter 03 Set 2013 17:02:28 BRT, Benjamin Root escreveu:
>
> On Mon, Sep 2, 2013 at 12:27 AM, Filipe Saraiva
> <ma...@fi... <mailto:ma...@fi...>> wrote:
>
>     Hello,
>
>     First, thanks for this great library.
>
>     My name is Filipe Saraiva, I am developing a python backend for
>     Cantor, the KDE mathematical software. More infos can be read in
>     http://blog.filipesaraiva.info/?tag=gsoc2013-python-backend (in
>     portuguese and english).
>
>     Currently I have a problem when I try import pyplot in Cantor. I
>     am using Python 2.7.5 and matplotlib 1.3.0. The error is below:
>
>     import matplotlib.pyplot as plt
>     Traceback (most recent call last):
>       File "<string>", line 1, in <module>
>       File "/usr/lib64/python2.7/site-packages/matplotlib/pyplot.py",
>     line 98, in <module>
>         _backend_mod, new_figure_manager, draw_if_interactive, _show =
>     pylab_setup()
>       File
>     "/usr/lib64/python2.7/site-packages/matplotlib/backends/__init__.py",
>     line 25, in pylab_setup
>         globals(),locals(),[backend_name])
>       File
>     "/usr/lib64/python2.7/site-packages/matplotlib/backends/backend_qt4agg.py",
>     line 19, in <module>
>         _decref = ctypes.pythonapi.Py_DecRef
>       File "/usr/lib64/python2.7/ctypes/__init__.py", line 378, in
>     __getattr__
>         func = self.__getitem__(name)
>       File "/usr/lib64/python2.7/ctypes/__init__.py", line 383, in
>     __getitem__
>         func = self._FuncPtr((name_or_ordinal, self))
>     AttributeError: kde/bin/cantor: undefined symbol: Py_DecRef
>
>     Well, anyone have any idea about how can I fix it?
>
>     Thank you,
>
>
> My only guess is that there is some sort of linking/build error.
> Perhaps the python-qt4 library was built and linked against a
> different python on your system?
>
> Cheers!
> Ben Root

Really I don't know. I will question it to matplotlib maintainer.

The pyplot import in python iteractive mode (python terminal) is 
working properly. I can run a matplotlib example using pyplot in this 
mode. I get the error just in Python/C API.

--
Filipe Saraiva
http://filipesaraiva.info/

Re: [matplotlib-devel] Error in import matplotlib.pyplot using Python/C API

[Michael D. <md...@st...>]

On 09/10/2013 08:23 AM, Filipe Saraiva wrote:
> Em Ter 03 Set 2013 17:02:28 BRT, Benjamin Root escreveu:
>> On Mon, Sep 2, 2013 at 12:27 AM, Filipe Saraiva
>> <ma...@fi... <mailto:ma...@fi...>> wrote:
>>
>>      Hello,
>>
>>      First, thanks for this great library.
>>
>>      My name is Filipe Saraiva, I am developing a python backend for
>>      Cantor, the KDE mathematical software. More infos can be read in
>>      http://blog.filipesaraiva.info/?tag=gsoc2013-python-backend (in
>>      portuguese and english).
>>
>>      Currently I have a problem when I try import pyplot in Cantor. I
>>      am using Python 2.7.5 and matplotlib 1.3.0. The error is below:
>>
>>      import matplotlib.pyplot as plt
>>      Traceback (most recent call last):
>>        File "<string>", line 1, in <module>
>>        File "/usr/lib64/python2.7/site-packages/matplotlib/pyplot.py",
>>      line 98, in <module>
>>          _backend_mod, new_figure_manager, draw_if_interactive, _show =
>>      pylab_setup()
>>        File
>>      "/usr/lib64/python2.7/site-packages/matplotlib/backends/__init__.py",
>>      line 25, in pylab_setup
>>          globals(),locals(),[backend_name])
>>        File
>>      "/usr/lib64/python2.7/site-packages/matplotlib/backends/backend_qt4agg.py",
>>      line 19, in <module>
>>          _decref = ctypes.pythonapi.Py_DecRef
>>        File "/usr/lib64/python2.7/ctypes/__init__.py", line 378, in
>>      __getattr__
>>          func = self.__getitem__(name)
>>        File "/usr/lib64/python2.7/ctypes/__init__.py", line 383, in
>>      __getitem__
>>          func = self._FuncPtr((name_or_ordinal, self))
>>      AttributeError: kde/bin/cantor: undefined symbol: Py_DecRef
>>
>>      Well, anyone have any idea about how can I fix it?
>>
>>      Thank you,
>>
>>
>> My only guess is that there is some sort of linking/build error.
>> Perhaps the python-qt4 library was built and linked against a
>> different python on your system?
>>
>> Cheers!
>> Ben Root
> Really I don't know. I will question it to matplotlib maintainer.
>
> The pyplot import in python iteractive mode (python terminal) is
> working properly. I can run a matplotlib example using pyplot in this
> mode. I get the error just in Python/C API.
>

It looks like it's failing inside of ctypes.  How are you including 
Python in your application.  Perhaps the ctypes module (which is a C 
extension module that comes in the Python standard library) is not being 
included or found.  I'm at a bit of a loss, but this seems like more of 
a general "embedding python in a C application" question, which you 
might try asking on the Python mailing list.

Mike

-- 
                    _
|\/|o _|_  _. _ | | \.__  __|__|_|_  _  _ ._ _
|  ||(_| |(_|(/_| |_/|(_)(/_|_ |_|_)(_)(_)| | |

http://www.droettboom.com

Re: [matplotlib-devel] Error in import matplotlib.pyplot using Python/C API

[Filipe S. <ma...@fi...>]

Em Ter 10 Set 2013 09:33:37 BRT, Michael Droettboom escreveu:
> On 09/10/2013 08:23 AM, Filipe Saraiva wrote:
>> Em Ter 03 Set 2013 17:02:28 BRT, Benjamin Root escreveu:
>>> On Mon, Sep 2, 2013 at 12:27 AM, Filipe Saraiva
>>> <ma...@fi... <mailto:ma...@fi...>> wrote:
>>>
>>>       Hello,
>>>
>>>       First, thanks for this great library.
>>>
>>>       My name is Filipe Saraiva, I am developing a python backend for
>>>       Cantor, the KDE mathematical software. More infos can be read in
>>>       http://blog.filipesaraiva.info/?tag=gsoc2013-python-backend (in
>>>       portuguese and english).
>>>
>>>       Currently I have a problem when I try import pyplot in Cantor. I
>>>       am using Python 2.7.5 and matplotlib 1.3.0. The error is below:
>>>
>>>       import matplotlib.pyplot as plt
>>>       Traceback (most recent call last):
>>>         File "<string>", line 1, in <module>
>>>         File "/usr/lib64/python2.7/site-packages/matplotlib/pyplot.py",
>>>       line 98, in <module>
>>>           _backend_mod, new_figure_manager, draw_if_interactive, _show =
>>>       pylab_setup()
>>>         File
>>>       "/usr/lib64/python2.7/site-packages/matplotlib/backends/__init__.py",
>>>       line 25, in pylab_setup
>>>           globals(),locals(),[backend_name])
>>>         File
>>>       "/usr/lib64/python2.7/site-packages/matplotlib/backends/backend_qt4agg.py",
>>>       line 19, in <module>
>>>           _decref = ctypes.pythonapi.Py_DecRef
>>>         File "/usr/lib64/python2.7/ctypes/__init__.py", line 378, in
>>>       __getattr__
>>>           func = self.__getitem__(name)
>>>         File "/usr/lib64/python2.7/ctypes/__init__.py", line 383, in
>>>       __getitem__
>>>           func = self._FuncPtr((name_or_ordinal, self))
>>>       AttributeError: kde/bin/cantor: undefined symbol: Py_DecRef
>>>
>>>       Well, anyone have any idea about how can I fix it?
>>>
>>>       Thank you,
>>>
>>>
>>> My only guess is that there is some sort of linking/build error.
>>> Perhaps the python-qt4 library was built and linked against a
>>> different python on your system?
>>>
>>> Cheers!
>>> Ben Root
>> Really I don't know. I will question it to matplotlib maintainer.
>>
>> The pyplot import in python iteractive mode (python terminal) is
>> working properly. I can run a matplotlib example using pyplot in this
>> mode. I get the error just in Python/C API.
>>
>
> It looks like it's failing inside of ctypes.  How are you including
> Python in your application.  Perhaps the ctypes module (which is a C
> extension module that comes in the Python standard library) is not being
> included or found.  I'm at a bit of a loss, but this seems like more of
> a general "embedding python in a C application" question, which you
> might try asking on the Python mailing list.
>
> Mike
>

I am using my code with several python modules and I can not get any 
error. I tried scipy, numpy, Spade, matplotlib... interesting, I don't 
get error when I import matplotlib.animation.

You can see reports of several uses of python commands and modules in 
my software accessing my blog in 
http://blog.filipesaraiva.info/?tag=gsoc2013-python-backend

Interesting, I used with success pyplot in the first version of this 
backend, last year. The blogpost have a picture of this 
http://blog.filipesaraiva.info/?p=779.

Well, I ask to another KDE developers for test my code and verify if 
the pyplot error that I am getting is reproducible.

Thank you,

--
Filipe Saraiva
http://filipesaraiva.info/

Re: [matplotlib-devel] Error in import matplotlib.pyplot using Python/C API

[Michael D. <md...@st...>]

On 09/10/2013 10:05 AM, Filipe Saraiva wrote:
> Em Ter 10 Set 2013 09:33:37 BRT, Michael Droettboom escreveu:
>> On 09/10/2013 08:23 AM, Filipe Saraiva wrote:
>>> Em Ter 03 Set 2013 17:02:28 BRT, Benjamin Root escreveu:
>>>> On Mon, Sep 2, 2013 at 12:27 AM, Filipe Saraiva
>>>> <ma...@fi... <mailto:ma...@fi...>> wrote:
>>>>
>>>>       Hello,
>>>>
>>>>       First, thanks for this great library.
>>>>
>>>>       My name is Filipe Saraiva, I am developing a python backend for
>>>>       Cantor, the KDE mathematical software. More infos can be read in
>>>> http://blog.filipesaraiva.info/?tag=gsoc2013-python-backend (in
>>>>       portuguese and english).
>>>>
>>>>       Currently I have a problem when I try import pyplot in Cantor. I
>>>>       am using Python 2.7.5 and matplotlib 1.3.0. The error is below:
>>>>
>>>>       import matplotlib.pyplot as plt
>>>>       Traceback (most recent call last):
>>>>         File "<string>", line 1, in <module>
>>>>         File 
>>>> "/usr/lib64/python2.7/site-packages/matplotlib/pyplot.py",
>>>>       line 98, in <module>
>>>>           _backend_mod, new_figure_manager, draw_if_interactive, 
>>>> _show =
>>>>       pylab_setup()
>>>>         File
>>>> "/usr/lib64/python2.7/site-packages/matplotlib/backends/__init__.py",
>>>>       line 25, in pylab_setup
>>>>           globals(),locals(),[backend_name])
>>>>         File
>>>> "/usr/lib64/python2.7/site-packages/matplotlib/backends/backend_qt4agg.py",
>>>>       line 19, in <module>
>>>>           _decref = ctypes.pythonapi.Py_DecRef
>>>>         File "/usr/lib64/python2.7/ctypes/__init__.py", line 378, in
>>>>       __getattr__
>>>>           func = self.__getitem__(name)
>>>>         File "/usr/lib64/python2.7/ctypes/__init__.py", line 383, in
>>>>       __getitem__
>>>>           func = self._FuncPtr((name_or_ordinal, self))
>>>>       AttributeError: kde/bin/cantor: undefined symbol: Py_DecRef
>>>>
>>>>       Well, anyone have any idea about how can I fix it?
>>>>
>>>>       Thank you,
>>>>
>>>>
>>>> My only guess is that there is some sort of linking/build error.
>>>> Perhaps the python-qt4 library was built and linked against a
>>>> different python on your system?
>>>>
>>>> Cheers!
>>>> Ben Root
>>> Really I don't know. I will question it to matplotlib maintainer.
>>>
>>> The pyplot import in python iteractive mode (python terminal) is
>>> working properly. I can run a matplotlib example using pyplot in this
>>> mode. I get the error just in Python/C API.
>>>
>>
>> It looks like it's failing inside of ctypes.  How are you including
>> Python in your application.  Perhaps the ctypes module (which is a C
>> extension module that comes in the Python standard library) is not being
>> included or found.  I'm at a bit of a loss, but this seems like more of
>> a general "embedding python in a C application" question, which you
>> might try asking on the Python mailing list.
>>
>> Mike
>>
>
> I am using my code with several python modules and I can not get any 
> error. I tried scipy, numpy, Spade, matplotlib... interesting, I don't 
> get error when I import matplotlib.animation.

Do any of those use ctypes?  Try creating a minimal ctypes example and 
see if that works.

Mike

-- 
                    _
|\/|o _|_  _. _ | | \.__  __|__|_|_  _  _ ._ _
|  ||(_| |(_|(/_| |_/|(_)(/_|_ |_|_)(_)(_)| | |

http://www.droettboom.com

Re: [matplotlib-devel] Error in import matplotlib.pyplot using Python/C API

[Eric F. <ef...@ha...>]

On 2013/09/10 5:43 AM, Michael Droettboom wrote:
> Do any of those use ctypes?  Try creating a minimal ctypes example and
> see if that works.

Mike,

I was a bit horrified to see that ctypes import and usage in mpl; 
fortunately it is a workaround for a PySide bug, and should only be 
temporary, if it should be there at all.

Eric

Re: [matplotlib-devel] Error in import matplotlib.pyplot using Python/C API

[Christoph G. <cg...@uc...>]

On 9/10/2013 1:54 PM, Eric Firing wrote:
> On 2013/09/10 5:43 AM, Michael Droettboom wrote:
>> Do any of those use ctypes?  Try creating a minimal ctypes example and
>> see if that works.
>
> Mike,
>
> I was a bit horrified to see that ctypes import and usage in mpl;
> fortunately it is a workaround for a PySide bug, and should only be
> temporary, if it should be there at all.
>
> Eric
>

Don't be horrified. The Ctypes workaround went trough the mailing list, 
a PR with discussions including most core developers, testing, several 
beta/rc/final versions, and real word usage. It fixes a problem that is 
still present today without it: the Qt4Agg backend is practically 
unusable with any recent version of PySide on CPython 3.x. Anyway, the 
Ctypes code could be put in a try/except statement for environments that 
don't support Ctypes or Python's C API.

Christoph

Re: [matplotlib-devel] Error in import matplotlib.pyplot using Python/C API

[Filipe S. <ma...@fi...>]

Em Ter 10 Set 2013 19:21:01 BRT, Christoph Gohlke escreveu:
> On 9/10/2013 1:54 PM, Eric Firing wrote:
>> On 2013/09/10 5:43 AM, Michael Droettboom wrote:
>>> Do any of those use ctypes?  Try creating a minimal ctypes example and
>>> see if that works.
>>
>> Mike,
>>
>> I was a bit horrified to see that ctypes import and usage in mpl;
>> fortunately it is a workaround for a PySide bug, and should only be
>> temporary, if it should be there at all.
>>
>> Eric
>>
>
> Don't be horrified. The Ctypes workaround went trough the mailing list,
> a PR with discussions including most core developers, testing, several
> beta/rc/final versions, and real word usage. It fixes a problem that is
> still present today without it: the Qt4Agg backend is practically
> unusable with any recent version of PySide on CPython 3.x. Anyway, the
> Ctypes code could be put in a try/except statement for environments that
> don't support Ctypes or Python's C API.

If I understood correctly is there a problem with Qt4Agg in matplotlib 
1.3?

Another KDE developer typed:

import matplotlib
from matplotlib import pyplot as plt

In my software (Cantor backend for python) and he got the error below:

Traceback (most recent call last):
File "", line 1, in
File "/usr/lib/python2.7/site-packages/matplotlib/pyplot.py", line 98, 
in
_backend_mod, new_figure_manager, draw_if_interactive, _show = 
pylab_setup()
File 
"/usr/lib/python2.7/site-packages/matplotlib/backends/__init__.py", line
25, in pylab_setup
globals(),locals(),[backend_name])
File 
"/usr/lib/python2.7/site-packages/matplotlib/backends/backend_qt4agg.py",
line 13, in
from backend_qt4 import QtCore, QtGui, FigureManagerQT, FigureCanvasQT,\
File 
"/usr/lib/python2.7/site-packages/matplotlib/backends/backend_qt4.py",
line 25, in
from qt4_compat import QtCore, QtGui, _getSaveFileName, __version__
File 
"/usr/lib/python2.7/site-packages/matplotlib/backends/qt4_compat.py",
line 36, in
import sip
ImportError: /usr/lib/python2.7/site-packages/sip.so: undefined symbol:
PyExc_SystemError

One more info, I removed matplotlib 1.3 and installed matplotlib 1.2 
using pip and it worked properly. I can use matplotlib in this version.

Thank you;

--
Filipe Saraiva
http://filipesaraiva.info/

Re: [matplotlib-devel] Error in import matplotlib.pyplot using Python/C API

[Eric F. <ef...@ha...>]

On 2013/09/11 8:49 AM, Filipe Saraiva wrote:
> Em Ter 10 Set 2013 19:21:01 BRT, Christoph Gohlke escreveu:
>> On 9/10/2013 1:54 PM, Eric Firing wrote:
>>> On 2013/09/10 5:43 AM, Michael Droettboom wrote:
>>>> Do any of those use ctypes?  Try creating a minimal ctypes example and
>>>> see if that works.
>>>
>>> Mike,
>>>
>>> I was a bit horrified to see that ctypes import and usage in mpl;
>>> fortunately it is a workaround for a PySide bug, and should only be
>>> temporary, if it should be there at all.
>>>
>>> Eric
>>>
>>
>> Don't be horrified. The Ctypes workaround went trough the mailing list,
>> a PR with discussions including most core developers, testing, several
>> beta/rc/final versions, and real word usage. It fixes a problem that is
>> still present today without it: the Qt4Agg backend is practically
>> unusable with any recent version of PySide on CPython 3.x. Anyway, the
>> Ctypes code could be put in a try/except statement for environments that
>> don't support Ctypes or Python's C API.
>
> If I understood correctly is there a problem with Qt4Agg in matplotlib
> 1.3?
>
> Another KDE developer typed:
>
> import matplotlib
> from matplotlib import pyplot as plt
>
> In my software (Cantor backend for python) and he got the error below:
>
> Traceback (most recent call last):
> File "", line 1, in
> File "/usr/lib/python2.7/site-packages/matplotlib/pyplot.py", line 98,
> in
> _backend_mod, new_figure_manager, draw_if_interactive, _show =
> pylab_setup()
> File
> "/usr/lib/python2.7/site-packages/matplotlib/backends/__init__.py", line
> 25, in pylab_setup
> globals(),locals(),[backend_name])
> File
> "/usr/lib/python2.7/site-packages/matplotlib/backends/backend_qt4agg.py",
> line 13, in
> from backend_qt4 import QtCore, QtGui, FigureManagerQT, FigureCanvasQT,\
> File
> "/usr/lib/python2.7/site-packages/matplotlib/backends/backend_qt4.py",
> line 25, in
> from qt4_compat import QtCore, QtGui, _getSaveFileName, __version__
> File
> "/usr/lib/python2.7/site-packages/matplotlib/backends/qt4_compat.py",
> line 36, in
> import sip
> ImportError: /usr/lib/python2.7/site-packages/sip.so: undefined symbol:
> PyExc_SystemError

Again, this is a failure of a module to find a Python API symbol.  In 
this case, it is not a matplotlib module, it is sip, part of pyqt4.  It 
seems like some sort of linking problem.

>
> One more info, I removed matplotlib 1.3 and installed matplotlib 1.2
> using pip and it worked properly. I can use matplotlib in this version.

I'm glad you found something that works; but I don't know why it does.

Eric

>
> Thank you;
>
> --
> Filipe Saraiva
> http://filipesaraiva.info/
>
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