How to find the frequency of the most frequent value (mode) of a series in polars?

Question

import polars as pl

df = pl.DataFrame({
    "tags": ["a", "a", "a", "b", "c", "c", "c", "c", "d"] 
})

This is how to compute the most frequent element of the column using the .mode expression:

df.select([
    pl.col("tags").mode().alias("mode"),
])

How can I display also the frequency/count of that mode?

Answer 1

I found this method, but I'm not sure if there's a better way:

df.select([
    pl.col("tags").mode().alias("mode"),
    pl.col("tags").filter(pl.col("tags") == pl.col("tags").mode()).count().alias("count")
])

Output:

shape: (1, 2)
????????????????
? mode ? count ?
? ---  ? ---   ?
? str  ? u32   ?
????????????????
? c    ? 4     ?
????????????????