Use list comprehension for expression functions

Question

Let’s say I want to make a list of functions, ie aggs=['sum','std','mean','min','max']

then if I have an arbitrary df

df=pl.DataFrame({'a':[1,2,3], 'b':[2,3,4]})

I want to be able to do something like (this obviously doesn’t work)

df.with_columns([pl.col('a').x() for x in aggs])

Is there a way to do that? aggs need not be a list of strings but just the easiest way to type out my intention for the purpose of this question. Additionally it’d need to have room for .suffix()

I know I could have a function that has all the aggs in the function and takes arbitrary dfs as a parameter which is like my backup plan so I’m hoping for something that resembles the above.

Asked By: Dean MacGregor

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Source

Answer 1

Would this work for you?

df.with_columns([getattr(pl.col("a"), x)().suffix("_" + x) for x in aggs])

shape: (3, 7)
┌─────┬─────┬───────┬───────┬────────┬───────┬───────┐
│ a   ┆ b   ┆ a_sum ┆ a_std ┆ a_mean ┆ a_min ┆ a_max │
│ --- ┆ --- ┆ ---   ┆ ---   ┆ ---    ┆ ---   ┆ ---   │
│ i64 ┆ i64 ┆ i64   ┆ f64   ┆ f64    ┆ i64   ┆ i64   │
╞═════╪═════╪═══════╪═══════╪════════╪═══════╪═══════╡
│ 1   ┆ 2   ┆ 6     ┆ 1.0   ┆ 2.0    ┆ 1     ┆ 3     │
│ 2   ┆ 3   ┆ 6     ┆ 1.0   ┆ 2.0    ┆ 1     ┆ 3     │
│ 3   ┆ 4   ┆ 6     ┆ 1.0   ┆ 2.0    ┆ 1     ┆ 3     │
└─────┴─────┴───────┴───────┴────────┴───────┴───────┘

Answered By: ΩΠΟΚΕΚΡΥΜΜΕΝΟΣ

Use list comprehension for expression functions

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