Getting legend for multilayer chart

Is it possible to make a legend for such a chart

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

x = np.arange(100)
data = pd.DataFrame({'x': x,
                     'sin(x)': np.sin(x / 5),
                     'data': np.sin(x / 5) + 0.3*np.random.rand(100)})

line = alt.Chart(data).mark_line(strokeWidth=6, color='orange').encode(
    x='x',
    y='sin(x)'
)

point = alt.Chart(data).mark_point(color='black').encode(
    x='x',
    y='data'
)
(line + point)

[jakevdp]

Yes, in newer versions of vega-lite you can set encodings to a constant datum value, which will be used to populate the legend. Altair doesn’t yet support this, though.

In Altair it would probably look something like this (Note that this does not work in the current release):

alt.Chart(data).mark_line().encode(
  x='x',
  y='y',
  color=alt.datum("My Line")
)

[ajasja]

Thanks! This is indeed a bit hacky:) But I got even a bit closer.

x = np.arange(100)
data = pd.DataFrame({'x': x,
                     'sin(x)': np.sin(x / 5),
                     'data': np.sin(x / 5) + 0.3*np.random.rand(100),
                     'line_label': 100 * ['line'],
                     'points_label': 100 * ['points']})

line = alt.Chart(data).mark_line(strokeWidth=6, color='orange').encode(
    x='x',
    y='sin(x)',
    opacity=alt.Opacity('line_label', legend=alt.Legend(title=""))
)

point = alt.Chart(data).mark_point(color='black').encode(
    x='x',
    y='data',
    shape=alt.Shape('points_label', legend=alt.Legend(title=""))
)
(line + point)

PS: this is probably a different debate (e.g. https://github.com/altair-viz/altair/issues/947); I just found out I could do

shape=alt.Shape('points_label', title="" )

instead of

shape=alt.Shape('points_label', legend=alt.Legend(title="") )

Big kudos points! 👍 Is this documented somewhere or is it a more try and see?