How to set Helvetica font for axes labels (numbers) with matplotlib with usetex on?

Question

I set the font style in the matplotlibrc param file to Helvetica (sans serif) which is already installed and I set text.usetex to 'true' but the axes fonts use serif fonts. My matplotlibrc parameter file is given below:

lines.linewidth : 1.0               # Line width (in points).
lines.linestyle : -                 # Line style.
lines.color : blue                  # Line color.


font.family : sans-serif
font.sans-serif : Helvetica, Arial, Bitstream Vera Sans, Lucida Grande, Verdana, Geneva, Lucid, Avant Garde, sans-serif

text.color : black
text.usetex : true


axes.facecolor : FFFFFF         # axes background color
axes.edgecolor : 000000         # axes edge color
axes.linewidth : 1.0            # edge linewidth
axes.grid : true                # display grid or not
axes.titlesize : large          # fontsize of the axes title
axes.labelsize : 9              # fontsize of the x any y labels
axes.labelweight : normal       # weight of the x and y labels
axes.labelcolor : 000000
axes.axisbelow : true
axes.formatter.limits : -7, 7
axes.color_cycle : E41A1C, 377EB8, 4DAF4A, 984EA3, FF7F00, FFFF33, A65628, F781BF, 999999       # color cycle for plot lines
polaraxes.grid : true           # display grid on polar axes
axes3d.grid : true              # display grid on 3d axes


xtick.major.size : 4            # Major tick size (in points).
xtick.minor.size : 2            # Minor tick size (in points).
xtick.major.width : 1           # Major tick width (in points).
xtick.minor.width : 1           # Minor tick width (in points).
xtick.major.pad : 6             # Distance to major tick label (in points).
xtick.minor.pad : 6             # Distance to the minor tick label (in points).
xtick.color : 000000            # Tick label colors.
xtick.labelsize : 8             # Tick label font size (in points).
xtick.direction : in            # Tick direction

ytick.major.size : 4            # Major tick size (in points).
ytick.minor.size : 2            # Minor tick size (in points).
ytick.major.width : 1           # Major tick width (in points).
ytick.minor.width : 1           # Minor tick width (in points).
ytick.major.pad : 6             # Distance to major tick label (in points).
ytick.minor.pad : 6             # Distance to the minor tick label (in points).
ytick.color : 000000            # Tick label colors.
ytick.labelsize : 8             # Tick label font size (in points).
ytick.direction : in            # Tick direction


grid.color : 999999             # Grid color.
grid.linestyle : :              # Grid line style.
grid.linewidth : 0.5            # Grid line width (in points).
grid.alpha : 1.0                # Grid line transparency.


legend.fancybox : true      # if true, use a rounded box for the
legend.isaxes : true
legend.numpoints : 1            # the number of points in the legend line
legend.fontsize : 9
legend.borderpad : 0.5          # border whitespace in fontsize units
legend.markerscale : 1.0        # the relative size of legend markers vs. original
legend.labelspacing : 0.5       # the vertical space between the legend entries in fraction of fontsize
legend.handlelength : 2.        # the length of the legend lines in fraction of fontsize
legend.handleheight : 0.7       # the height of the legend handle in fraction of fontsize
legend.handletextpad : 0.8      # the space between the legend line and legend text in fraction of fontsize
legend.borderaxespad : 0.5      # the border between the axes and legend edge in fraction of fontsize
legend.columnspacing : 2.       # the border between the axes and legend edge in fraction of fontsize
legend.shadow : false
legend.frameon : true           # whether or not to draw a frame around legend
legend.scatterpoints : 1        # number of scatter points

How do I get the axes fonts to use Helvetica sans?

Update

I tried using the code:

plt.rcParams['font.family'] = 'Helvetica'

But this is the error I get:

/usr/lib/pymodules/python2.7/matplotlib/font_manager.py:1236: UserWarning: findfont: Font family ['Helvetica'] not found. Falling back to Bitstream Vera Sans
  (prop.get_family(), self.defaultFamily[fontext]))
/usr/lib/pymodules/python2.7/matplotlib/font_manager.py:1246: UserWarning: findfont: Could not match :family=Bitstream Vera Sans:style=normal:variant=normal:weight=normal:stretch=normal:size=medium. Returning /usr/share/matplotlib/mpl-data/fonts/ttf/cmb10.ttf
  UserWarning)
/usr/lib/pymodules/python2.7/matplotlib/font_manager.py:1246: UserWarning: findfont: Could not match :family=Bitstream Vera Sans:style=normal:variant=normal:weight=normal:stretch=normal:size=large. Returning /usr/share/matplotlib/mpl-data/fonts/ttf/cmb10.ttf
  UserWarning)

Answer 1

Have you added the .ttf files to where matplotlib can find them? "Installed" for the OS may not mean "installed" for matplotlib . Check out this blog post: http://blog.olgabotvinnik.com/blog/2012/11/15/2012-11-15-how-to-set-helvetica-as-the-default-sans-serif-font-in/

Answer 2

Adding this to my matplotlibrc file worked for me.

mathtext.fontset : custom
mathtext.it : Helvetica:italic

Also, I needed to have Helvetica-Oblique.ttf in my /usr/local/anaconda3/lib/python3.7/site-packages/matplotlib/mpl-data/fonts/ttf directory. Olga Botvinnik has some good instructions in her answer here and in her blog.

Note, that you're going to have to clear out your cache under ~/.matplotlib in order to refresh this.

Matplotlib says that custom fontsets are not supported and this might all break in a future update of Matplotlib.