Unable to use latex in python plots - RuntimeError: LaTeX was not able to process the following string: b'lp'

Question

I want to use latex for the labels of a figure but I get the error
RuntimeError: LaTeX was not able to process the following string: b'lp'
Here is the full report generated by LaTeX:
and that is it (I don't see any report)

Edit : Here is the whole error I obtain:

Traceback (most recent call last):
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\backends\backend_qt5agg.py", line 197, in __draw_idle_agg
    FigureCanvasAgg.draw(self)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\backends\backend_agg.py", line 464, in draw
    self.figure.draw(self.renderer)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\artist.py", line 63, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\figure.py", line 1144, in draw
    renderer, self, dsu, self.suppressComposite)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\image.py", line 139, in _draw_list_compositing_images
    a.draw(renderer)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\artist.py", line 63, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\axes\_base.py", line 2426, in draw
    mimage._draw_list_compositing_images(renderer, self, dsu)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\image.py", line 139, in _draw_list_compositing_images
    a.draw(renderer)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\artist.py", line 63, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\axis.py", line 1138, in draw
    renderer)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\axis.py", line 1078, in _get_tick_bboxes
    extent = tick.label1.get_window_extent(renderer)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\text.py", line 967, in get_window_extent
    bbox, info, descent = self._get_layout(self._renderer)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\text.py", line 353, in _get_layout
    ismath=False)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\backends\backend_agg.py", line 230, in get_text_width_height_descent
    renderer=self)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\texmanager.py", line 676, in get_text_width_height_descent
    dvifile = self.make_dvi(tex, fontsize)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\texmanager.py", line 423, in make_dvi
    report))
RuntimeError: LaTeX was not able to process the following string:
b'lp'
Here is the full report generated by LaTeX: 

Here is my code:

import numpy as np
from matplotlib import rc
import matplotlib.pyplot as plt
plt.close('all')

rc('text', usetex = True)

mu = np.linspace(0,10,100)
eta = mu**2

fig, ax = plt.subplots()
ax.plot(mu,eta,label= r'$\eta (\mu)$')
ax.set_title('Test')
ax.legend()

• I installed MiKTeX, added it to the environment variables according to https://docs.alfresco.com/4.2/tasks/fot-addpath.html.
  
• I checked the packages of MiKTeX, where I found "miktex-dvipng-bin-x64-2.9" in the "\MiKTeX excecutables" category. I deduce I have a dvipng.
  
• I dowloaded Ghostcript, which I also added to the environment variables.
  
• I tried compiling a latex script to pdf using texworks, and it worked just fine, from what I deduce LaTeX is properly installed.
  
• From https://matplotlib.org/1.4.1/users/usetex.html, this is all I was supposed to need...
  
• I tried deleting my .matplotlib/tex.cache directory
  
• I tried writting

import matplotlib as mpl
mpl.rcParams['text.usetex']=True

instead of

from matplotlib import rc
rc('text', usetex = True)

but it yielded the same result.

• Swiching
  

rc('text', usetex = True)

to

rc('text', usetex = False)

prevents the error, but my labels are not written with latex...

After a lot of googling, I'm short with ideas. Could anyone help me please?

My configuration is:
- Python 3.6 (I run my code in spyder)
- MiKTeX 2.9
- Ghostscript 9.50
- Windows 10
- Edit : matplotlib 2.0.2

Edit : upgrading to matplotlib 3.1.1, I get the following error:

Traceback (most recent call last):
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\texmanager.py", line 304, in _run_checked_subprocess
    stderr=subprocess.STDOUT)
  File "C:\Users\Vincent\Anaconda3\lib\subprocess.py", line 336, in check_output
    **kwargs).stdout
  File "C:\Users\Vincent\Anaconda3\lib\subprocess.py", line 403, in run
    with Popen(*popenargs, **kwargs) as process:
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\spyder\utils\site\sitecustomize.py", line 209, in __init__
    super(SubprocessPopen, self).__init__(*args, **kwargs)
  File "C:\Users\Vincent\Anaconda3\lib\subprocess.py", line 707, in __init__
    restore_signals, start_new_session)
  File "C:\Users\Vincent\Anaconda3\lib\subprocess.py", line 992, in _execute_child
    startupinfo)
FileNotFoundError: [WinError 2] Le fichier spécifié est introuvable

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\backends\backend_qt5.py", line 505, in _draw_idle
    self.draw()
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\backends\backend_agg.py", line 388, in draw
    self.figure.draw(self.renderer)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\artist.py", line 38, in draw_wrapper
    return draw(artist, renderer, *args, **kwargs)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\figure.py", line 1709, in draw
    renderer, self, artists, self.suppressComposite)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\image.py", line 135, in _draw_list_compositing_images
    a.draw(renderer)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\artist.py", line 38, in draw_wrapper
    return draw(artist, renderer, *args, **kwargs)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\axes\_base.py", line 2607, in draw
    self._update_title_position(renderer)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\axes\_base.py", line 2556, in _update_title_position
    if title.get_window_extent(renderer).ymin < top:
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\text.py", line 890, in get_window_extent
    bbox, info, descent = self._get_layout(self._renderer)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\text.py", line 291, in _get_layout
    ismath="TeX" if self.get_usetex() else False)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\backends\backend_agg.py", line 201, in get_text_width_height_descent
    s, fontsize, renderer=self)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\texmanager.py", line 448, in get_text_width_height_descent
    dvifile = self.make_dvi(tex, fontsize)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\texmanager.py", line 338, in make_dvi
    texfile], tex)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\texmanager.py", line 308, in _run_checked_subprocess
    'found'.format(command[0])) from exc
RuntimeError: Failed to process string with tex because latex could not be found
Traceback (most recent call last):
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\texmanager.py", line 304, in _run_checked_subprocess
    stderr=subprocess.STDOUT)
  File "C:\Users\Vincent\Anaconda3\lib\subprocess.py", line 336, in check_output
    **kwargs).stdout
  File "C:\Users\Vincent\Anaconda3\lib\subprocess.py", line 403, in run
    with Popen(*popenargs, **kwargs) as process:
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\spyder\utils\site\sitecustomize.py", line 209, in __init__
    super(SubprocessPopen, self).__init__(*args, **kwargs)
  File "C:\Users\Vincent\Anaconda3\lib\subprocess.py", line 707, in __init__
    restore_signals, start_new_session)
  File "C:\Users\Vincent\Anaconda3\lib\subprocess.py", line 992, in _execute_child
    startupinfo)
FileNotFoundError: [WinError 2] Le fichier spécifié est introuvable

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\backends\backend_qt5.py", line 505, in _draw_idle
    self.draw()
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\backends\backend_agg.py", line 388, in draw
    self.figure.draw(self.renderer)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\artist.py", line 38, in draw_wrapper
    return draw(artist, renderer, *args, **kwargs)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\figure.py", line 1709, in draw
    renderer, self, artists, self.suppressComposite)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\image.py", line 135, in _draw_list_compositing_images
    a.draw(renderer)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\artist.py", line 38, in draw_wrapper
    return draw(artist, renderer, *args, **kwargs)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\axes\_base.py", line 2607, in draw
    self._update_title_position(renderer)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\axes\_base.py", line 2556, in _update_title_position
    if title.get_window_extent(renderer).ymin < top:
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\text.py", line 890, in get_window_extent
    bbox, info, descent = self._get_layout(self._renderer)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\text.py", line 291, in _get_layout
    ismath="TeX" if self.get_usetex() else False)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\backends\backend_agg.py", line 201, in get_text_width_height_descent
    s, fontsize, renderer=self)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\texmanager.py", line 448, in get_text_width_height_descent
    dvifile = self.make_dvi(tex, fontsize)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\texmanager.py", line 338, in make_dvi
    texfile], tex)
  File "C:\Users\Vincent\Anaconda3\lib\site-packages\matplotlib\texmanager.py", line 308, in _run_checked_subprocess
    'found'.format(command[0])) from exc
RuntimeError: Failed to process string with tex because latex could not be found

Answer 1

I fixed the issue by installing texlive-fonts-extra on Ubuntu 18.04.

sudo apt-get install texlive-fonts-extra

Answer 2

For about the 5th time I unistalled and reinstalled MikTeX, and this time my problem is solved. When running my python script, three windows opened successively asking for packages installations. I attach to this answer screenshots of these three windows. After accepting to install these packages, my script worked just fine. Previously, when unistalling and reinstalling MikTeX, I already saw windows asking for installation and accepted the installations. I don't know why this time it worked whilst it didn't work before... Anyway, my problem was solved uninstalling and reinstalling MiKTeX, running my script and accepting packages.

Window for installation of a file from type1cm

Window for installation of a file from iftex

Window for installation of a file from zhmetrics