How to use mapped values for numerical chart axis ticks

Say I have a variable, df, that contains some data that looks like this in pandas

Date          Number Letter
2017-10-31    2      B
2019-08-31    1      A
2021-11-30    3      C
...

I'd like to chart this out in seaborn, so I use some code like this

sb.lineplot(data=df, x=Date, y=Number)
plt.show()

And I get an orderly line chart that looks something like this

However, i'd like to have the y axis tick labels to preserve the numerical order of the number column, but present as labels from the letter column. For instance, instead of the y axis being 10 - 17 as above, i'd like the y axis to read j - t.

Is there a way to implement that through the sb.lineplot arguments, or would I need another way?

Solution

IIUC, you can use FixedLocator and FixedFormatter:

import matplotlib.ticker as ticker

ax = sb.lineplot(data=df, x='Date', y='Number')
ax.yaxis.set_major_locator(ticker.FixedLocator(df['Number']))
ax.yaxis.set_major_formatter(ticker.FixedFormatter(df['Letter']))
plt.show()

Output: