Altair Show Axis Tick Labels As Percentage Point

I would like to format axis tick labels as percentage point.

import altair as alt
from vega_datasets import data

source = data.jobs.url

alt.Chart(source).mark_line().encode(
    alt.X('year:O'),
    alt.Y('perc:Q').axis(format='%'),
    alt.Color('sex:N')
).transform_filter(
    alt.datum.job == 'Welder'
)

So in the example above (taken from here), it should show the y-axis tick labels as '<value>%pt' instead of <value>% - is this possible to achieve?

If I understand you correctly, you want to add a pt suffix to each label. You can do this via labelExpr:

alt.Y('perc:Q').axis(labelExpr='100 * datum.value + "%pt"'),