optional `file_index:int` column when using `source:list[str] | list[Path]` with `scan_*` about polars

[gszep]

a current workaround can be

dfs = [ ]
for i,path in enumerate(Path(data_dir).glob(pattern)):
    df = pl.scan_csv(path).with_columns(file_index=pl.lit(i, dtype=pl.Int32))
    dfs.append(df)
df = pl.concat(dfs)
df.filter( pl.col("file_index") == file_index ).collect()

[cmdlineluser]

Just with regards to the functionality: a variation of this that came up previously was adding the filepath as a column.

• #9096

Wouldn't this be useful to have in the readers as it could also be used when passing a remote-glob directly? e.g. pl.scan_csv("http://.../*/foo*csv")

(DuckDB has filename=true which seems to do this.)