I’m working with a Polars DataFrame, and I want to combine two columns into a dictionary format, where the values from one column become the keys and the values from the other column become the corresponding values.

Here’s an example DataFrame:

import polars as pl

df = pl.DataFrame({
    "name": ["Chuck", "John", "Alice"],
    "surname": ["Dalliston", "Doe", "Smith"]
})

I want to transform this DataFrame into a new column that contains dictionaries, where name is the key and surname is the value. The expected outcome should look like this:

shape: (3, 3)
┌───────┬─────────┬──────────────────────────┐
│ name  │ surname │ name_surname             │
│ ---   │ ---     │ ---                      │
│ str   │ str     │ dict[str, str]           │
├───────┼─────────┼──────────────────────────┤
│ Chuck │ Dalliston│ {"Chuck": "Dalliston"}   │
│ John  │ Doe     │ {"John": "Doe"}          │
│ Alice │ Smith   │ {"Alice": "Smith"}       │
└───────┴─────────┴──────────────────────────┘

I’ve tried the following code:

df.with_columns(
    json = pl.struct("name", "surname").map_elements(json.dumps)
)

But the result is not as expected. Instead of creating a dictionary with key-value, it produces:

{name:Chuck,surname:Dalliston}