Rust Polars Dataframe String replacement

Question

I am writing a Rust using Polars. I would like to know how can I manipulate one string dataframe column.

For example, I have the following dataframe:

Id	Text
1	Some foo text
2	Other text

And I would like to replace all values that has "foo" by some other value like "new foo" and I wasn't able to find a way to do that. Can anyone help me on this?

I tried to use the function with_column, but I didn't manage how to do it.

Answer 1

You can do like the following:

use polars::prelude::*;
use polars::df;
use regex::Regex;

fn main() {
    // use macro
    let mut df = df! [
        "Id" => [1,2],
        "Text" => ["Some foo text", "Other text",],
    ].unwrap();

    println!("before = {:?}", df);
    
    let re = Regex::new(r"foo").unwrap();
    let target = "new foo";

    let new_foo_series = df.column("Text").unwrap()
        .utf8()
        .unwrap()
        .apply(|e| re.replace(e, target));
    
    let df2 = df.with_column(new_foo_series).unwrap();
    
    println!("after = {:?}", df2);

}

That will show:

before = shape: (2, 2)
┌─────┬───────────────┐
│ Id  ┆ Text          │
│ --- ┆ ---           │
│ i32 ┆ str           │
╞═════╪═══════════════╡
│ 1   ┆ Some foo text │
│ 2   ┆ Other text    │
└─────┴───────────────┘
after = shape: (2, 2)
┌─────┬───────────────────┐
│ Id  ┆ Text              │
│ --- ┆ ---               │
│ i32 ┆ str               │
╞═════╪═══════════════════╡
│ 1   ┆ Some new foo text │
│ 2   ┆ Other text        │
└─────┴───────────────────┘

Ref = https://docs.rs/polars/latest/polars/docs/eager/index.html#apply-functions-closures