Creating Polars Dataframe from Vec<Struct>

Question

Supposing I have a vector of structs like so:

struct Test {
    id:u32,
    amount:u32
 }
 
 fn main() {
    let test_vec:Vec<Test> = vec![Test{id:1,amount:3}, Test{id:3,amount:4}];
 }

Is there a way to get this into a polars dataframe with the column names being the struct fields?

Hoping to get an output as follows:

   id  amount
0   1       3
1   3       4

Answer 1

After a lot of head banging, I found the following solution.

If you have a vector of a custom struct, to get it into a Polars dataframe you can do the following:

// 1. Derive serde::Serialize for your struct

#[derive(Serialize)]
struct Test {
    id:u32,
    amount:u32
}

// (Adding new method here for quality of life).

impl Test {
    fn new(id:u32, amount:u32) -> Self{
        Test{id,amount}
    }
}


// 2. Jsonify your struct Vec
let test_vec:Vec<Test> = vec![Test::new(1,3), Test::new(3,4)];
let json = serde_json::to_string(&test_vec).unwrap();

// 3. Create cursor from json 
let cursor = Cursor::new(json);

// 4. Create polars DataFrame from reading cursor as json
let df = JsonReader::new(cursor)
            .finish()
            .unwrap();