Can you please provide your ~/.cache/matplotlib/fontlist-v300.json before and after deleting ~/.cache/matplotlib (and reimporting matplotlib to regenerate the json)? Thanks.

Quick update. Issue occurred again last night (running jupyter notebooks as batch jobs).

I deleted ~/.cache/matplotlib and the issue resolved. I also reimported matplotlib but it didn't regenerate the json?

I'll keep an eye on it.

"import matplotlib.font_manager" should regenerate it.

I had to do it outside jupyter - seems to be ignoring %load_ext autoreload

I've attached the fontlist-v300.json files before and after deleting ~/.cache/matplotlib

fontlist-v300-after.zip
fontlist-v300-before.zip

Thanks. The caches look fine and I don't see how these can trigger the warning for now :/
I guess you can try

fm = matplotlib.font_manager.json_load("/path/to/fontlist-v300.json")
fm.findfont("serif", rebuild_if_missing=False)
fm.findfont("serif", fontext="afm", rebuild_if_missing=False)

when the warning happens. Do these trigger the warning (in a fresh session)? Can you, say, debug-print the scoring in _findfont_cached()?

I've been playing with a minimal notebook - if I restart kernel and clear outputs, the first time I run the cells below I get the warnings, the 2nd time there's no warning and the 2nd font found is different.

i.e. first run through after restarting kernel:

import matplotlib.pyplot as plt
from matplotlib import rc
rc('font',**{'family':'serif','serif':['Computer Modern Roman']})
rc('text', usetex=True)

import matplotlib.font_manager
import os
fm = matplotlib.font_manager.json_load(os.path.expanduser("~/.cache/matplotlib/fontlist-v300.json"))

fm.findfont("serif", rebuild_if_missing=False)

/home/david/.pyenv/versions/3.7.1/envs/jupyter-3.7.1/lib/python3.7/site-packages/matplotlib/font_manager.py:1241: UserWarning: findfont: Font family ['serif'] not found. Falling back to DejaVu Sans.
(prop.get_family(), self.defaultFamily[fontext]))
'/home/david/.pyenv/versions/3.7.1/envs/jupyter-3.7.1/lib/python3.7/site-packages/matplotlib/mpl-data/fonts/ttf/DejaVuSans.ttf'

fm.findfont("serif", fontext="afm", rebuild_if_missing=False)

/home/david/.pyenv/versions/3.7.1/envs/jupyter-3.7.1/lib/python3.7/site-packages/matplotlib/font_manager.py:1241: UserWarning: findfont: Font family ['serif'] not found. Falling back to Helvetica.
(prop.get_family(), self.defaultFamily[fontext]))
'/home/david/.pyenv/versions/3.7.1/envs/jupyter-3.7.1/lib/python3.7/site-packages/matplotlib/mpl-data/fonts/pdfcorefonts/Helvetica.afm'

2nd (and subsequent) run:

import matplotlib.pyplot as plt
from matplotlib import rc
rc('font',**{'family':'serif','serif':['Computer Modern Roman']})
rc('text', usetex=True)

import matplotlib.font_manager
import os
fm = matplotlib.font_manager.json_load(os.path.expanduser("~/.cache/matplotlib/fontlist-v300.json"))

fm.findfont("serif", rebuild_if_missing=False)

'/home/david/.pyenv/versions/3.7.1/envs/jupyter-3.7.1/lib/python3.7/site-packages/matplotlib/mpl-data/fonts/ttf/DejaVuSans.ttf'

fm.findfont("serif", fontext="afm", rebuild_if_missing=False)

'/home/david/.pyenv/versions/3.7.1/envs/jupyter-3.7.1/lib/python3.7/site-packages/matplotlib/mpl-data/fonts/afm/phvr8a.afm'

PS System python is 3.6, I'm running pyenv using python 3.7.1 and a virtualenv (called jupyter-3.7.1) if that's of any relevance. In particular it seems that the fonts are stored in a per virtualenv folder but the cache is shared across all python environments on the machine which could potentially cause issues - I'm only using the one pyenv though.

In theory the cache should be reusable across venvs (as long as they all have mpl>=3 (not sure of the exact lower bound)).

When you say no warning on the 2nd+ run, do you mean after restarting the kernel in between? Otherwise that's normal, that's due to the fact that Python keeps track of already emitted warnings and does not emit duplicate warnings (by default).

I still don't understand why deleting and regenerating the cache helps (can you provide your matplotlibrc? possibly relevant).
However I see at least one "bug" (say, inaccuracy) in the text layouting code now: even when usetex is True, we try to get the font extent using ismath=False, and that's apparently what triggers the warning (because then you need the font, e.g. Computer Modern Roman in your case, to actually be findable by non-tex machinery :/)

The 2nd+ run has no restart of the kernel - note though it appears to have found the correct (non-fallback) font on the second run?

No? It's still falling back to dejavusans (the afm case is irrelevant I think).
I think it's just that the warning doesn't get printed out a second time (I think?).

OK, the afm case did change though? Presumably it should be deterministic

run 1:
'/home/david/.pyenv/versions/3.7.1/envs/jupyter-3.7.1/lib/python3.7/site-packages/matplotlib/mpl-data/fonts/pdfcorefonts/Helvetica.afm'

run 2:
'/home/david/.pyenv/versions/3.7.1/envs/jupyter-3.7.1/lib/python3.7/site-packages/matplotlib/mpl-data/fonts/afm/phvr8a.afm'

Perhaps it should, but it's not clear it is... (both of these fonts are Helvetica)

I missed your request to provide my matplotlibrc.zip

matplotlib.matplotlib_fname()
'/home/david/.pyenv/versions/3.7.1/envs/jupyter-3.7.1/lib/python3.7/site-packages/matplotlib/mpl-da

I've not customised it, there's nothing in $HOME/.config/matplotlib

possible related to #13137

To the best of my guess this should be closed by #13170, @david-waterworth can you try matplotlib master?

@anntzer I'm still seeing the warning on master

i.e. (now I get the warning each time, and the reported font path is the same)

import matplotlib
import os
fm = matplotlib.font_manager.json_load(os.path.expanduser("~/.cache/matplotlib/fontlist-v310.json"))
fm.findfont("serif", rebuild_if_missing=False)

findfont: Font family ['serif'] not found. Falling back to DejaVu Sans.
'/home/david/matplotlib/lib/matplotlib/mpl-data/fonts/ttf/DejaVuSans.ttf'

fm.findfont("serif", fontext="afm", rebuild_if_missing=False)

findfont: Font family ['serif'] not found. Falling back to Helvetica.
'/home/david/matplotlib/lib/matplotlib/mpl-data/fonts/pdfcorefonts/Helvetica.afm'

That's expected; but what about the actual original use case?

Thanks @anntzer, master appears to have fixed the original issue (it does now throw an exception with the latex preamble I was using, but I understand that's not supported anyway and I don't need it at this stage)

This is good to close then?

I think so. Thanks!

findfont: Font family ['Times New Roman'] not found. Falling back to DejaVu Sans

Matplotlib version: 3.1.2

@thangckt please open a new issue with reproducible steps. Thanks...

@thangckt I think Matplotlib does not provide all fonts. You need to download the font file and install it so that Matplotlib can use it.

I had the same problem on macOS with matplotlib 4.3.4, I could solve it by deleting

~/.matplotlib/fontlist-v330.json

and then restarting jupyter notebook

findfont: Font family ['serif'] not found. Falling back to DejaVu Sans.

This issue still persists. Jupyter run from PyCharm. Lib version is 3.5.1.

Try matplotlib.font_manager._rebuild()

@oscargus I get this AttributeError: module 'matplotlib.font_manager' has no attribute '_rebuild'

I'm suddenly getting this error on macOS 10.12.6, first with matplotlib 3.4.2 and just now 3.5.1 after upgrading. Removing ~/.matplotlib/fontlist-v330.json had no effect. Running matplotlib.font_manager._rebuild() gave the same error as hkayann above. It was working fine a few months ago when making plots, and I can't think of any major system changes that might have changed anything.

In my case, the error says findfont: Generic family 'serif' not found because none of the following families were found: stix, cm10 (which are specified in my matplotlibrc file), but grepping for "stix" and "cm" in fontlist-v330.json turns up plenty of hits for both.

Please provide your fontlist-v330.json? (and also whether this is with usetex on or off)

Here's my fontlist-v330.json file, and this is with usetex on (specifically, via matplotlibrc file).

I guess we'll need a complete repro example. There's no font named "stix" or "cm10" in your fontlist.json, and trying to use such fonts in font.serif with usetex results in

No LaTeX-compatible font found for the serif fontfamily in rcParams. Using default.

if one additionally has plt.set_loglevel("info").

Thanks for taking a look. I was able to fix the problem by simply commenting out the line font.serif : stix, cm10 in my matplotlibrc file, which gave me serif fonts in my plot again (since font.family : serif is still uncommented, presumably). I'm not sure why that worked, but I'm content to leave it here now that it's working again, since it looks like a local configuration issue. Thanks for the help.

A full repro example would still be useful, if only so that this doesn't occur again (or perhaps we can make the configuration problem more obvious, etc.).

Ok, I'll try to get one this weekend, I'm pressed for time this week.

No hurries.

Same issue. I tried both the solutions proposed here:

• matplotlib.font_manager._rebuild()
• removing everything in ~/.cache/matplotlib/ and then restarting Jupyter notebook.

Neither work for me

@sakshamg94 can you try the steps I provided on SO.

@sakshamg94 can you try the steps I provided on SO.

didn't help...

Why this bug remains unsolved to this day....

Having the same issue but in my case:
findfont: Font family ['Heiti TC'] not found. Falling back to DejaVu Sans.

I have the same issue
findfont: Font family ['century-gothic'] not found. Falling back to DejaVu Sans.

Maybe.

import platform
import os

system = platform.system()

if system == 'Darwin':  # macOS
  font_path = '/System/Library/Fonts/STHeiti Light.ttc'
elif system == 'Windows':
  font_path = 'C:/Windows/Fonts/simhei.ttf'
else:  #  unix
  font_path = 'simhei.ttf'

custom_font = fm.FontProperties(fname=font_path)

I am having a similar issue. I have been trying to set fonts as follows:

matplotlib.rcParams['font.family'] = "sans-serif" matplotlib.rcParams['font.sans-serif'] = "Arial"

I have also tried with matplotli.pyplot but keep getting the following message:

findfont: Generic family 'sans-serif' not found because none of the following families were found: Arial

I have looked at the fonts cache and apparently there are not Arial fonts. I have tried removing the cache and regenerating it but the error persists.

fontlist-v300.zip

@jaweriaamjad it seems like you do not have Arial installed, so that seems like the most likely problem. (Arial is a Microsoft font and it looks from the paths like you are not using Windows? Helvetica is a good replacement, as in Arial is a "copy" of Helvetica.)

I have problem to display chinese, I solved the problem by following these steps:

• Download SimHei.ttf font file from internet and save it to python directory, for me, it's /Users/<username>/venv_3_9/lib/python3.9/site-packages/matplotlib/mpl-data/fonts/ttf
• Delete ~/.cache/matplotlib and ~/.matplotlib/*.json
• Find and delete all metadata of Font file, such as xattr -l SimHei.ttf, xattr -d com.apple.quarantine SimHei.ttf
• Set font in python script: import matplotlib.pyplot as plt, plt.rcParams['font.sans-serif'] = ['SimHei']

If it doesn't work , try to reload python environment: cd /Users/<username>/venv_3_9/bin && deactivate && source ./activate

Download SimHei.ttf font file from internet and save it to python directory, for me, it's /Users/<username>/venv_3_9/lib/python3.9/site-packages/matplotlib/mpl-data/fonts/ttf

There is no need to put fonts in a system/package directory like this. Matplotlib will read fonts from standard system paths.

Humble attempt here. I am using Ubuntu WSL on Windows and had the same issues anytime I tried to plot anything with matplotlib. I noticed that by doing the following imports the warnings finally disappear:
import matplotlib as mpl
import matplotlib.pyplot as plt

For me the solution was to add import matplotlib as mpl. Hope this can solve the issue!