Develop Reference

matplotlib.pyplot giving error 'ImportError: No module named Tkinter' on python 2.7

I'm using a remote machine for computation and data analysis. I don't have sudo access in this machine, for data analysis purposes I want to use python libraries such as vtk etc since pip is not installed in this machine, I set up a 'virtual-environment' and install VTK there,
I used the method explained here (https://stackoverflow.com/a/13958308/10755782). Then I could install vtk in the virtual environment using pip.
But now the problem is that I can't import matplotlib.pyplot, it is giving me the error
ImportError: No module named Tkinter.
This error is strange because matplotlib.pyplot works in this particular system outside my virtual-environment. There are a few workarounds to start using matplotlib.pyplot without tkinter such as this (https://stackoverflow.com/a/49988926/10755782), but this is not helpfull in my case as this machine is remote-accessed and I need 'tkinter' to view the graphs on my screen.
I tried installing 'tkinter' inside my virtual-env, but I could not ( since we can't install 'tkinter' with pip and I don't have sudo access).
As I could not find any immediate solution to this problem anywhere I tried to fix this myself and I did the following,
inside my virtual environment, the version of matplotlib was 2.2.4 and outside it was 1.2.0 ( which is working fine). So I downgraded the version of matplotlib inside my virtual environment to 1.2.0
pip install 'matplotlib==1.2.0' --force-reinstall
now I have the same version of matplotlib inside and outside the virtual env. But now, when I try import matplotlilb.pyplot as plt I'm getting the error
ImportError: /b/home/ipcms/rcheenik/Python_virt-env/python2.7/my_new_env/lib/python2.7/site-
packages/matplotlib/_cntr.so: undefined symbol: _intel_fast_memset
Is there any way to fix this ^^ error? any of these following will be able to help me.
without OR is there any way to install tkinter without sudo ? or inside the 'virtual-environment' ?
OR is there any alternatives to matplotlib.pyplot which works without 'tkinter' and still display graphs remotely? ( not favourable, as I have to rewrite the entire code )
Thanks in advance for the help.

I found this answer to a similar question however, which I believe would solve your issue.
https://stackoverflow.com/a/49988926/8775307
It imports matplotlib.pyplot without tkinter. I don't know if all the features are actually included though, so you'll have to test and let us know :).
You could always write to the administrator and request Tkinter - it's a widely used and useful package, so they might be willing to include it.

Which backend for matplotlib using MacOS?

The question of using matplotlib with MacOS is a tricky one which has already been thoroughly reviewed by a number of discussions (see below). The problem is the following:
using MacOS Mojave 10.14.3
using python 3.7.2 in a conda environment
using matplotlib 3.0.3
Here is the simplest code snippet I came up with which allows reproducing the issue:
from matplotlib import pyplot as plt
x = [1, 2, 3]
y = [1, 2, 3]
plt.plot(x, y)
plt.show()
This throws the following error:
2019-03-22 12:25:43.429 python3.7[22209:554135] -[NSApplication _setup:]: unrecognized selector sent to instance 0x7f85866b9de0
2019-03-22 12:25:43.431 python3.7[22209:554135] \*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSApplication _setup:]: unrecognized selector sent to instance 0x7f85866b9de0'
*** First throw call stack:([...])
libc++abi.dylib: terminating with uncaught exception of type NSException
Process finished with exit code 134 (interrupted by signal 6: SIGABRT)
The issue is documented here. One solution is to install the PyQt5 package to your Python installation and to add the following lines at the beginning of your script:
import matplotlib
matplotlib.use("Qt5Agg")
While this works perfectly well, I am wondering why other backends fail to provide similar behavior.
Indeed I tried using MacOSX backend :
import matplotlib
matplotlib.use('MACOSX')
Which yields to the error:
from matplotlib.backends import _macosx
ImportError: Python is not installed as a framework. The Mac OS X backend will not be able to function correctly if Python is not installed as a framework. See the Python documentation for more information on installing Python as a framework on Mac OS X. Please either reinstall Python as a framework or try one of the other backends. If you are using (Ana)Conda please install python.app and replace the use of 'python' with 'pythonw'. See 'Working with Matplotlib on OSX' in the Matplotlib FAQ for more information.
The issue is documented here, there and in plenty of other threads.
Two solutions came out :
install python.app(conda install python.app) and launch your script with pythonw instead of python
use TKAggbackend
Using the first one works well but I wonder:
why do we need to call pythonw instead of python ?
what exactly is the python.app package ?
how can we make this solution work using an IDE (let say PyCharm for instance) ?
As for the second one, it does "work" up to a certain point: when running matplotlib using TkAgg, the plot window is really buggy. Indeed, it often needs several clicks on the "zoom", "pan" or "home" buttons to get them to actually work. It really is a great pain to use it. I asked several colleagues or friends using matplotlib with TkAgg and they all have the same issue.
Does anyone know the reason for this state of fact? Or if there is any workaround to avoid this issue (apart from installing pyqt5)?

Using the first option is your best bet since you are already working with a virtual environment.
According to matplotlib, there are two variants of python:
A Framework build - Quite important for GUI stuffs in MacOXs
A regular build.
Matplotlib in this case would want to interact natively with OSX and for this, it needs the Framework build this is the reason why installing the python.app type of python is important.
More information can be gotten from Matplotlib FAQ.
Check this link for more about the need for a framework build python.

I'm going to make some assumptions. If they're wrong I apologize.
You installed Python with Anaconda.
Personally, I've never had any problems on mac with matplotlib. My setup is: Mojave, Python3.7.3 in a venv using the python built in module (python3 -m venv), and matplotlib 3.0.3.
I can't answer your question on how to fix your problem, but I'm kind of trying to answer your "is there any workaround" question. Personally, I've always had issues with using Anaconda/Spyder/Conda for Python. I've always felt installing it as its own binary/app on the system leads to the fewest errors.
Now, I'm not saying you have to download and install by hand though. I use homebrew and it saves me headaches everyday I assume (such as upgrading applications and packages). That's the "work around" I'd suggest. Because isn't installing via Anaconda/Spyder already a workaround to installing Python properly? I've always felt performing one work around requires more workarounds for full functionality. Such as having to specify the matplotlib backend when it should be detected by default.
Obviously, I'm a little biased against that tool and that may be reflected in this answer, so take it with a grain of salt. Even though Conda is a legitimate tool that I think is useful, I find it annoying having to use both pip and conda when conda doesn't contain the packages I want.

There are two things you can try.
You can read Matplotlib info page on that, https://matplotlib.org/3.1.0/faq/osx_framework.html,
The default python provided in (Ana)conda is not a framework build. However, a framework build can easily be installed, both in the main environment and in conda envs: install python.app (conda install python.app) and use pythonw rather than python.
And follow the instructions.
Or simply follow the error message you get when you try %matplotlib inline,
(...)
UnknownBackend: No event loop integration for 'inline'. Supported event loops are: qt, qt4, qt5, gtk, gtk2, gtk3, tk, wx, pyglet, glut, osx
I did %matplotlib osx and have plt.imshow(myimg) working just fine afterwards.

'module 'matplotlib' has no attribute 'pyplot''

When trying to import pyplot from matplotlib, I get this error (python 3.6). It works fine on my other computer, which has python 3.5, but I don't think it changed much.
I've tried both:
from matplotlib import pyplot as plt
and
import matplotlib.pyplot as plt
It's really annoying me that I can't figure this out.

matplotlib targets many different use cases and output formats. Some people use matplotlib interactively from the python shell and have plotting windows pop up when they type commands. Some people embed matplotlib into graphical user interfaces like wxpython or pygtk to build rich applications. Others use matplotlib in batch scripts to generate postscript images from some numerical simulations, and still others in web application servers to dynamically serve up graphs.
To support all of these use cases, matplotlib can target different outputs, and each of these capabilities is called a backend; the “frontend” is the user facing code, i.e., the plotting code, whereas the “backend” does all the hard work behind-the-scenes to make the figure. There are two types of backends: user interface backends (for use in pygtk, wxpython, tkinter, qt4, or macosx; also referred to as “interactive backends”) and hardcopy backends to make image files (PNG, SVG, PDF, PS; also referred to as “non-interactive backends”).
In yout case you have to choose backend "Agg" to use pyplot.
Solution:
import matplotlib
matplotlib.use("Agg")
import matplotlib.pyplot as plt
reference:
https://matplotlib.org/tutorials/introductory/usage.html#what-is-a-backend
https://github.com/matplotlib/matplotlib/issues/9954

Let me guess:
1:Maybe you have not properly installed matplotlib, you can try this:
pip3.6 install --upgrade matplotlib
Or just deleted the package and reinstall
2:Check whether you have use the same config environment and execution environment:
In some cases, you have installed packages for your local python interpreter, but you actually run your program on python virtual env. Maybe you have not properly installed the package on virtual env.

PyQt5 gets "No module named 'PyQt4'" error calling matplotlib.pyplot in Python 3.5

I am using Anaconda with Python 3.5.2, Matplotlib 2.0.2, PyQt5.6 on a windows 10 machine. When I import matplotlib.pyplot as plt I get the following error:
...
File "C:...\Anaconda3\Lib\site-packages\matplotlib\backends\qt_compat.py",
line 137, in <module> from PyQt4 import QtCore, QtGui
ImportError: No module named 'PyQt4'
I don't know why it would want to import from PyQt4 when it has never been installed on my machine.
This question has the same error, but on a machine that actually has PyQt4 installed.
I have checked my matplotlibrc file, I've used matplotlib.use('qt5agg') in the program, also matplotlib.rcParams['backend'] = "Qt5Agg". I've uninstalled and reinstalled all the above packages to no avail. I have even attempted to install PyQt4 just to get things going. I'm completely stumped. None of the various possible causes or remedies that I've been able to find on either SO or github have helped.

I just had the same error (even though on Windows 7). For me the problem was that there was an old matplotlibrc file in C:\Users\<username>\.matplotlib\matplotlibrc which overwrote the settings from my environment's matplotlibrc file. Deleting that file solved the issue for me.

It seems the API version is PyQt5 but the default is PyQt4,just open Tools -> Preferences -> IPython console -> Graphics -> backend,change QT4 to QT5

Looking at the file and line number in your error it looks that you have the same issue that I answered here.
That is, I think your issue is caused by having a QT_API environment variable that still is set to pyqt4 (or pyside).

I ran into a similar thing and found that the problem was having a 64-bit Anaconda installation that couldn't load the PyPt5 DLLs that were perhaps 32-bit. The short answer is that I uninstalled Anaconda 64-bit and installed the 32-bit version instead.
To work through this, I stepped through qt_compat.py where the error originates. For most of the time through this module, it’s trying to work with PyQt5, as that’s what it finds in the environment. However, when it gets to the lines below, the import fails so it tries to fall back to PyQt4, which isn’t installed with Anaconda, and thus issues the error.
if QT_API == QT_API_PYQT5:
try:
from PyQt5 import QtCore, QtGui, QtWidgets
_getSaveFileName = QtWidgets.QFileDialog.getSaveFileName
except ImportError:
# fell through, tried PyQt5, failed fall back to PyQt4
QT_API = rcParams['backend.qt4']
QT_RC_MAJOR_VERSION = 4
Testing the import statement outside of the file gave the message “DLL load failed: %1 is not a valid Win32 application.” That's what suggests the DLL mismatch, and also answers why it was trying to fall back to PyQt4.

3 steps can solve this problem:
pip uninstall pyqt5
pip uninstall matplotlib
pip install matplotlib

I had faced the same problem and here is how I fixed it.
Look into your matplotlib configuration file which is often located at
path-to/site-packages/matplotlib/mpl-data/matplotlibrc
or
path-to/Anaconda3/envs/your_env_name/Lib/site-packages/matplotlib/mpl-data/matplotlibrc
See an example of matplotlibrc here
https://github.com/daler/matplotlibrc/blob/master/rc/default
If you have pyqt5.x.x installed and have the statement 'backend : Qt5Agg' in matplotlibrc, then to use '%matplotlib qt', change '#backend.qt4 : PyQt4' to '#backend.qt4 : PyQt5'.
For an Anaconda environment, reactivate the environment.
Note if you update matplotlib in the future, your matplotlibrc will automatically be overwritten.

matplotlib example code not working on python virtual environment

I am trying to display the x y z coordinate of an image in matplotlib. the example code work perfectly well on the global python installation: As I move the cursor the x,y,z values get updated instantaneously. However, when I run the example code on a python virtual environment, I would click on the images several times for the coordinate to show in the first place, then when I click on different positions it would update for some. After few clicks, the coordinates will no longer update.
I don't know how to debug this.

This is likely to be a problem with the macosx backend for matplotlib. Switch to using an alternative backend for matplotlib (e.g. use qt4 instead of 'macosx'). For details of how to switch backend and what exactly that means - see the docs here. Note that you might have to install the backend first - e.g. pyqt to use the qt4agg backend as I'm suggesting here.
In summary - the backend deals with the output from matplotlib and matplotlib can target different output formats. These can be gui display output formats (for instance wx, qt4 and so on), or file outputs (for instance pdf). These are known as interactive and non-interactive backends respectively.
To change backend either do
import matplotlib
matplotlib.use('qt4agg')
in code, or - if you want to change for every time you start matplotlib - edit your matplotlibrc file setting the backend attribute e.g.
backend: Qt4Agg
N.B. I was alerted by a comment that since posting this answer, matplotlib docs now refer to this issue and suggest a workaround, although the commenter noted that the solution offered in this answer (switch to Qt backend) worked for them where the official docs workaround was not possible for them.

What finally worked for me was to make a local matplotlibrc file containing the directive: backend: TkAgg.
# Within working directory where running python
vim matplotlibrc
# new file via vim, Nano, whatever
backend: TkAgg
This was useful:
import matplotlib
print matplotlib.rcParams['backend']
Other Notes:
I had also installed pyqt using Homebrew (brew install pyqt) and copied (could just move it) into $MyVirtEnv/lib/python2.7/site-packages/ from /usr/local/lib/python2.7/site-packages/PyQt4
But when I
import matplotlib
matplotlib.use('qt4Agg')
import librosa
"Matplotlib qt-based backends require an external PyQt4, PyQt5,\n"
ImportError: Matplotlib qt-based backends require an external PyQt4, PyQt5,
or PySide package to be installed, but it was not found.
Had also tried
pip install pyside
Successfully installed pyside-1.2.4
Same error
>>> import pyside
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: No module named pyside
Also got the following error at some point when trying to reimport matplotlib (i think).
from . import cache
ImportError: cannot import name cache

As pointed out in Matplotlib virtualenv FAQ, vext is the solution here.
It allows to use the system-wide pyqt5 for instance.
This is necessary until PyQt5 setup knows about virtualenvs:
pip3 install vext.pyqt5

Just add plt.show() at the end and the problem was solved for me.