Possible Windows-only error on save() to PNG

[asarmy]

Getting an error using Altair saver when I am trying to save a chart to a PNG in Jupyter Notebook: ValueError: Unsupported format: 'png'

Answer here on Stack Overflow suggested filing a bug report.

System info:

Windows 10 conda 4.8.2 Python 3.8.3 altair 4.1.0 py_1 conda-forge altair_saver 0.1.0 py_0 conda-forge vega 3.4.0 py38h32f6830_0 conda-forge selenium 3.141.0 py38h9de7a3e_1001 conda-forge

Example Code:

import pandas as pd
import altair as alt
from altair_saver import save
alt.renderers.enable('default'); # if in jupyter, ; to suppress output
alt.renderers.enable('altair_saver', fmts=['vega-lite', 'png']);

mytaskbars = pd.DataFrame([
    {"task": "Task1a", "start": '2020-06-01', "end": '2020-09-30', "color": 'royalblue'},
    {"task": "Task1b", "start": '2020-06-01', "end": '2021-03-31', "color": 'deepskyblue'},
    {"task": "Task2", "start": '2020-06-01', "end": '2021-03-31', "color": 'red'},
    ])
    
mytaskbars["start"] = pd.to_datetime(mytaskbars["start"])
mytaskbars["end"] = pd.to_datetime(mytaskbars["end"])
    
    
chart = alt.Chart(mytaskbars).mark_bar(opacity=0.7).encode(
    x=alt.X('start', axis=alt.Axis(title='Date', labelAngle=-45, format = ("%b %Y"))),
     x2 = 'end',
    y=alt.Y('task', axis=alt.Axis(title=None)),
    color = alt.Color('color:N', scale = None)
    )
    
save(chart, "chart_202006.png")
chart

Error Message:

ValueError                                Traceback (most recent call last)
<ipython-input-3-13a284c2aca9> in <module>
     19     )
     20 
---> 21 save(chart, "chart_202006.png")
     22 chart

~\anaconda3\envs\geospat_env\lib\site-packages\altair_saver\_core.py in save(chart, fp, fmt, mode, method, **kwargs)
     60     """
     61     if method is None:
---> 62         Saver = _get_saver_for_format(fmt=fmt, fp=fp)
     63     elif isinstance(method, type):
     64         Saver = method

~\anaconda3\envs\geospat_env\lib\site-packages\altair_saver\_core.py in _get_saver_for_format(fmt, fp)
     28         if fmt in s.valid_formats and s.enabled():
     29             return s
---> 30     raise ValueError(f"Unsupported format: {fmt!r}")
     31 
     32 

ValueError: Unsupported format: 'png'

[jakevdp]

Thanks – I don't have a windows machine to debug this, so if you're able to figure out the issue and submit a fix, that would be very helpful!

[stanmart]

Can confirm it on my system as well. It looks to be an issue with altair_saver, not Altair itself. Also, most likely related to https://github.com/altair-viz/altair_saver/issues/70 It is supposedly fixed in the newer versions of altair_saver, but due to their dependence on vega-cli and vega-lite-cli they cannot be installed on Windows.

[awa5114]

Is there a workaround to this?

[jakevdp]

I don't know of any workaround. I don't have access to a Windows machine to try it out. Perhaps someone who has access to a windows machine might volunteer to work on it?

[nickcorona]

MAN! I have this same issue.

[Amarounek]

Same issue with svg format. :-(

[balrog-nona]

I have the same issue after upgradig from Fedora 31 to Fedora 32. It worked perfectly with Fedora 31, but with Fedora 32, the code

import altair as alt
base = alt.Chart(data_df).properties(width=500)  # creating Chart object
line = base.mark_line(color='crimson').encode(x='date', y='kms')  # data visualization using Line Chart
rule = base.mark_rule(color='coral').encode(y='average(kms)', size=alt.value(2))  # line for average kms
my_chart = line + rule
my_chart.save('chart.png')

goes with this error:

Traceback (most recent call last):
  File "main.py", line 130, in <module>
    my_chart.save('chart.png')
  File "/home/balrog/.local/lib/python3.8/site-packages/altair/vegalite/v4/api.py", line 476, in save
    result = save(**kwds)
  File "/home/balrog/.local/lib/python3.8/site-packages/altair/utils/save.py", line 112, in save
    mimebundle = spec_to_mimebundle(
  File "/home/balrog/.local/lib/python3.8/site-packages/altair/utils/mimebundle.py", line 60, in spec_to_mimebundle
    return altair_saver.render(spec, format, mode=mode, **kwargs)
  File "/home/balrog/.local/lib/python3.8/site-packages/altair_saver/_core.py", line 255, in render
    Saver = _select_saver(method, mode=mode, fmt=fmt)
  File "/home/balrog/.local/lib/python3.8/site-packages/altair_saver/_core.py", line 69, in _select_saver
    raise ValueError(f"No enabled saver found that supports format={fmt!r}")
ValueError: No enabled saver found that supports format='png'

Thanks for any suggestions how to fix it.

[jakevdp]

@balrog-nona This is unrealted to the windows error in this issue. You need to install additional requirements in order to save to PNG; see the installation instructions here: https://github.com/altair-viz/altair_saver#additional-requirements

[balrog-nona]

@jakevdp Thank you for the link. Looks like I'll have to configure geckodriver.

[dkruszew]

I encountered the same issue while running the altair_saver.save() function on my Windows 10 machine: i.e this error: No enabled saver found that supports format='png'.

Investigating the error led me to the below code within _core.py in the altair_saver package, which indicated that the error statement I was receiving was likely due to the below if statement failing for each saver method:

for s in _SAVER_METHODS.values():
    if s.enabled() and fmt in s.valid_formats[mode]:
        return s
raise ValueError(f"No enabled saver found that supports format={fmt!r}")

I originally thought that the above if statements were failing because of the file format png in s.valid_formats[mode]. Upon investigation I discovered the png string was fine, and the issue appeared to exist within s.enabled(). I did some further digging where I played with the method and webdriver arguments in the save function. When respectively using method=selenium with webdriver=chrome I received an error that told me my chromedriver.exe file was out of date for my chrome browser. I re-downloaded from here and replaced the file in C:\Windows. After doing so the save function worked seamlessly.

[Jtuppack]

I find the error No enabled saver found that supports format='png' to be very temperamental. Previously I had it working and successfully outputting to a .png but since opening a new instance of my Jupyter notebook I'm getting the error again.

@dkruszew would it be possible to share more of your code, namely the save function?

[thefabnab]

I'm seeing the same issue right now as well. Temperamental would be the way I'd characterize it as well.

[jhermann]

FYI, I solved this on Win10 / WSL1 by .venv/bin/npm install vega-lite vega-cli canvas into a mixed Python/Node virtualenv.

[hoctro01]

Hi, i used atlair_save debug with PyCharm working fine. But i run code with service on ubuntu then error "No enabled saver found that supports format='png'" Can you help me!

ubuntu 20.04 python 3.8.10 altair-4.1.0 altair_saver-0.5.0

[joelostblom]

@hoctro01 Try following the troubleshooting steps in the altair-saver installation instructions https://github.com/altair-viz/altair_saver/#installation

[hoctro01]

I have installed and run code with terminal or pycharm on ubuntu ok, but i puslish systemd service ubuntu not working ("No enabled saver found that supports format='png'")

[Unit] Description=TestBotService After=network.target [Service] Type=simple User=root ExecStart=/home/vtn-bot/miniconda3/envs/ipkv_bot/bin/python /home/vtn-bot/ipkv_bot/bot_test.py Restart=always RestartSec=3 [Install] WantedBy=multi-user.target

[jhermann]

You need to find out the difference in your shell env vs. the systemd one -- starting with the fact you run this as root. If you try the ExecStart command in a root shell that might enlighten you as to a cause.

Or look into systemd user services and run as vtn-bot.