Altair: chart.save does not support pdf as shown in docs

[dlukes]

The docs for saving charts show chart.save('chart.pdf') as one of the options, but running that results in ValueError: unrecognized format: 'pdf', even though altair_saver is installed and from altair_saver import save; save(chart, "chart.pdf") works.

By contrast, chart.save("chart.svg") works fine.

Looking at the docstring of Chart.save, it looks like pdf isn't even supposed to work: "Supported formats are json, html, png, svg". But maybe it's just a matter of wiring it up?

If the issue is more complicated than that (maybe because Chart.save is currently hardwired to use the Selenium backend, which doesn't offer pdf export?), then I would suggest just removing chart.save('chart.pdf') from the code example and refer users who are interested in pdf export functionality to altair_saver's docs :)

[jakevdp]

This requires altair version 4.1 or later. Check what version you are using with

import altair
print(altair.__version__)

[dlukes]

4.1.0, I've just installed it... But maybe I've misconfigured it then?

[jakevdp]

Ah, yeah, you're right. the mimebundle code has been updated, but we neglected to thread through the save method for pdf. This is a bug.

[jakevdp]

What error do you get when trying to save a png? I'm surprised that doesn't work, because (unlike PDF) it's covered in the test suite in several places.

[dlukes]

Thanks for resolving this so quickly!

[ADR777]

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
Created on Sat Apr  4 22:40:59 2020

@author: a
"""


import altair as alt
print(alt.__version__)
alt.renderers.enable('altair_viewer')
#alt.renderers.enable('html')
# load a simple dataset as a pandas DataFrame
from vega_datasets import data
cars = data.cars()

chart = alt.Chart(cars).mark_point().encode(
    x='Horsepower',
    y='Miles_per_Gallon',
    color='Origin',
).interactive()

#chart.show()
chart.save('filename.html')
chart.save('filename.pdf')
#chart.save("TESTS_/charty4_1.pdf")

This results in the error messages:

runfile('/home/a/ADR/SPYDER_CODE/example.py', wdir='/home/a/ADR/SPYDER_CODE')
4.1.0
Traceback (most recent call last):

  File "/home/a/ADR/SPYDER_CODE/example.py", line 26, in <module>
    chart.save('filename.pdf')

  File "/home/a/anaconda3/lib/python3.7/site-packages/altair/vegalite/v4/api.py", line 476, in save
    result = save(**kwds)

  File "/home/a/anaconda3/lib/python3.7/site-packages/altair/utils/save.py", line 128, in save
    raise ValueError("unrecognized format: '{}'".format(format))

ValueError: unrecognized format: 'pdf'`

Is something still wrong with the pdf save?

[jakevdp]

Yes, pdf save is still broken in version 4.1. The fix above is only a few hours old and has not made it into a release yet.

[ADR777]

Thank you kindly Jake.

I would like to sincerely congratulate you on the 4.0 - 4.1 releases.
Excellent improvements.

[noureddine-as]

Hi,

I installed both Altair and Altair_saver last dev versions using the following commands

pip3 install git+https://github.com/altair-viz/altair       
# Successfully installed altair-4.2.0.dev0
pip3 install git+https://github.com/altair-viz/altair_saver
#Successfully installed altair-saver-0.6.0.dev0

But I didn't succeed to export as PDF

4.2.0.dev0
Traceback (most recent call last):
  File "stacked_bar_example_pd.py", line 56, in <module>
    chart.save('chart.pdf')
  File "/home/aitsaidn/.local/lib/python3.6/site-packages/altair/vegalite/v4/api.py", line 477, in save
    result = save(**kwds)
  File "/home/aitsaidn/.local/lib/python3.6/site-packages/altair/utils/save.py", line 121, in save
    **kwargs,
  File "/home/aitsaidn/.local/lib/python3.6/site-packages/altair/utils/mimebundle.py", line 60, in spec_to_mimebundle
    return altair_saver.render(spec, format, mode=mode, **kwargs)
  File "/home/aitsaidn/.local/lib/python3.6/site-packages/altair_saver/_core.py", line 255, in render
    Saver = _select_saver(method, mode=mode, fmt=fmt)
  File "/home/aitsaidn/.local/lib/python3.6/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='pdf'

Here is the Example I'm using

import pandas as pd
import numpy as np
import altair as alt

# Generate Random Data

df1=pd.DataFrame(10*np.random.rand(4,3),index=["A","B","C","D"],columns=["I","J","K"])
df2=pd.DataFrame(10*np.random.rand(4,3),index=["A","B","C","D"],columns=["I","J","K"])
df3=pd.DataFrame(10*np.random.rand(4,3),index=["A","B","C","D"],columns=["I","J","K"])

def prep_df(df, name):
    df = df.stack().reset_index()
    df.columns = ['c1', 'c2', 'values']
    df['DF'] = name
    return df

df1 = prep_df(df1, 'DF1')
df2 = prep_df(df2, 'DF2')
df3 = prep_df(df3, 'DF3')

df = pd.concat([df1, df2, df3])


# Plotting
chart = alt.Chart(df).mark_bar().encode(

    # tell Altair which field to group columns on
    x=alt.X('c2:N', title=None),

    # tell Altair which field to use as Y values and how to calculate
    y=alt.Y('sum(values):Q',
        axis=alt.Axis(
            grid=False,
            title=None)),

    # tell Altair which field to use to use as the set of columns to be  represented in each group
    column=alt.Column('c1:N', title=None),

    # tell Altair which field to use for color segmentation 
    color=alt.Color('DF:N',
            scale=alt.Scale(
                # make it look pretty with an enjoyable color pallet
                range=['#96ceb4', '#ffcc5c','#ff6f69'],
            ),
        ))\
    .configure_view(
        # remove grid lines around column clusters
        strokeOpacity=0    
    )

print(alt.__version__)
chart.save('chart.pdf')

Any ideas to resolve that?

Thanks in advance.
Best regards.

[jakevdp]

To save as PDF, you need the vega-cli tools installed and correctly configured, as described in the documentation

[ADR777]

(base) a@a-HP-EliteBook-820-G1:~$ sudo -s
[sudo] password for a:
(base) root@a-HP-EliteBook-820-G1:~# npm install vega-lite vega-cli canvas

[email protected] install /home/a/node_modules/canvas
node-pre-gyp install --fallback-to-build

node-pre-gyp WARN Using needle for node-pre-gyp https download
node-pre-gyp WARN Pre-built binaries not installable for [email protected] and [email protected] (node-v64 ABI, glibc) (falling back to source compile with node-gyp)
node-pre-gyp WARN Hit error EACCES: permission denied, mkdir '/home/a/node_modules/canvas/build'
gyp ERR! configure error
gyp ERR! stack Error: EACCES: permission denied, mkdir '/home/a/node_modules/canvas/build'
gyp ERR! System Linux 5.3.0-42-generic
gyp ERR! command "/home/a/anaconda3/bin/node" "/home/a/anaconda3/lib/node_modules/npm/node_modules/node-gyp/bin/node-gyp.js" "configure" "--fallback-to-build" "--module=/home/a/node_modules/canvas/build/Release/canvas.node" "--module_name=canvas" "--module_path=/home/a/node_modules/canvas/build/Release" "--napi_version=3" "--node_abi_napi=napi" "--napi_build_version=0" "--node_napi_label=node-v64"
gyp ERR! cwd /home/a/node_modules/canvas
gyp ERR! node -v v10.13.0
gyp ERR! node-gyp -v v3.8.0
gyp ERR! not ok
node-pre-gyp ERR! build error
node-pre-gyp ERR! stack Error: Failed to execute '/home/a/anaconda3/bin/node /home/a/anaconda3/lib/node_modules/npm/node_modules/node-gyp/bin/node-gyp.js configure --fallback-to-build --module=/home/a/node_modules/canvas/build/Release/canvas.node --module_name=canvas --module_path=/home/a/node_modules/canvas/build/Release --napi_version=3 --node_abi_napi=napi --napi_build_version=0 --node_napi_label=node-v64' (1)
node-pre-gyp ERR! stack at ChildProcess. (/home/a/node_modules/node-pre-gyp/lib/util/compile.js:83:29)
node-pre-gyp ERR! stack at ChildProcess.emit (events.js:182:13)
node-pre-gyp ERR! stack at maybeClose (internal/child_process.js:962:16)
node-pre-gyp ERR! stack at Process.ChildProcess._handle.onexit (internal/child_process.js:251:5)
node-pre-gyp ERR! System Linux 5.3.0-42-generic
node-pre-gyp ERR! command "/home/a/anaconda3/bin/node" "/home/a/node_modules/.bin/node-pre-gyp" "install" "--fallback-to-build"
node-pre-gyp ERR! cwd /home/a/node_modules/canvas
node-pre-gyp ERR! node -v v10.13.0
node-pre-gyp ERR! node-pre-gyp -v v0.11.0
node-pre-gyp ERR! not ok
Failed to execute '/home/a/anaconda3/bin/node /home/a/anaconda3/lib/node_modules/npm/node_modules/node-gyp/bin/node-gyp.js configure --fallback-to-build --module=/home/a/node_modules/canvas/build/Release/canvas.node --module_name=canvas --module_path=/home/a/node_modules/canvas/build/Release --napi_version=3 --node_abi_napi=napi --napi_build_version=0 --node_napi_label=node-v64' (1)
npm WARN enoent ENOENT: no such file or directory, open '/home/a/package.json'
npm WARN [email protected] requires a peer of vega@^5.12.1 but none is installed. You must install peer dependencies yourself.
npm WARN a No description
npm WARN a No repository field.
npm WARN a No README data
npm WARN a No license field.

npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! [email protected] install: node-pre-gyp install --fallback-to-build
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the [email protected] install script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR! /home/a/.npm/_logs/2020-05-24T11_51_59_632Z-debug.log