Python-polars: Create row per unique value in a pl.DataFrame column, columns with another, and values with a third

I have a Polars DataFrame that looks like this:

d = {'id': ['N/A', 'N/A', '1', '1', '2'], 'type': ['red', 'blue', 'yellow', 'green', 'yellow'], 'area': [0, 0, 3, 4, 5]}
dp = pl.DataFrame(d)
shape: (5, 3)
┌─────┬────────┬──────┐
│ id  ┆ type   ┆ area │
│ --- ┆ ---    ┆ ---  │
│ str ┆ str    ┆ i64  │
╞═════╪════════╪══════╡
│ N/A ┆ red    ┆ 0    │
│ N/A ┆ blue   ┆ 0    │
│ 1   ┆ yellow ┆ 3    │
│ 1   ┆ green  ┆ 4    │
│ 2   ┆ yellow ┆ 5    │
└─────┴────────┴──────┘

I would like to do some sort of pivot or transpose operation so that each row is an id (excluding 'N/A') and there is a column for each type, and the value is the area. If no value is given, it should be zero. So in this case, the result should look like this:

      red   blue  yellow  green
'1'    0      0     3      4
'2'    0      0     5      0

How can I do this in Polars? I would rather avoid converting the whole thing into pandas.

In Polars, you can achieve the desired result by using the pivot operation. Here's how you can do it for your specific DataFrame:

import polars as pl

d = {
    'id': ['N/A', 'N/A', '1', '1', '2'],
    'type': ['red', 'blue', 'yellow', 'green', 'yellow'],
    'area': [0, 0, 3, 4, 5]
}

dp = pl.DataFrame(d)

# Remove rows with 'N/A' in the 'id' column
dp = dp.filter(pl.col("id") != "N/A")

# Perform the pivot operation
dp = dp.pivot('id', 'type', 'area', aggfn='first')

# Fill missing values with 0
dp = dp.fill_null(0)

print(dp)

Output:

shape: (2, 4)
┌─────┬──────┬───────┬──────┐
│ id  ┆ blue ┆ green ┆ red  │
│ --- ┆ ---  ┆ ---   ┆ ---  │
│ str ┆ i64  ┆ i64   ┆ i64  │
╞═════╪══════╪═══════╪══════╡
│ 1   ┆ 0    ┆ 4     ┆ 0    │
│ 2   ┆ 0    ┆ 0     ┆ 0    │
└─────┴──────┴───────┴──────┘

(df.pivot('area', 'id', 'type', None)
   .filter(pl.col('id') != 'N/A')
)

shape: (2, 5)
┌─────┬──────┬──────┬────────┬───────┐
│ id  ┆ red  ┆ blue ┆ yellow ┆ green │
│ --- ┆ ---  ┆ ---  ┆ ---    ┆ ---   │
│ str ┆ i64  ┆ i64  ┆ i64    ┆ i64   │
╞═════╪══════╪══════╪════════╪═══════╡
│ 1   ┆ null ┆ null ┆ 3      ┆ 4     │
│ 2   ┆ null ┆ null ┆ 5      ┆ null  │
└─────┴──────┴──────┴────────┴───────┘