Error constructing DataFrame from dict scalar about polars HOT 5 CLOSED

@stinodego: linked to the constructor refactor?

from polars.

Probably. I'm not sure this ever used to work though. The problem seems to be in arrlen where it infers length 2 for the struct 'scalar'.

from polars.

Probably. I'm not sure this ever used to work though. The problem seems to be in arrlen where it infers length 2 for the struct 'scalar'.

@stinodego: Ahh, I think you're right - I assumed this was a regression, but installing some earlier versions of Polars to check further makes me think it is not ;)

@linusheinz: Did this ever work for you in a different version of Polars?
(And, if so, which version?)

from polars.

I just checked back to 20.9, and it did not work. It seems to be present in many versions.

from polars.

I just checked back to 20.9, and it did not work. It seems to be present in many versions.

Note that the easiest way to address this is to provide sequence data in the dict, which is the expected form (as each value in the dict represents a column).

pl.DataFrame({"test": [0], "nest": [{"test": 0, "test2": 0}]})
# shape: (1, 2)
# ┌─────┬───────────┐
# │ x   ┆ nest      │
# │ --- ┆ ---       │
# │ i64 ┆ struct[2] │
# ╞═════╪═══════════╡
# │ 0   ┆ {0,0}     │
# └─────┴───────────┘

Passing non-sequence data here is a little hit and miss, as we typically expand it in a fast-path for quick generation of large frames with repetitive data, like so:

pl.DataFrame({"n": range(1000), "y": -1})
# shape: (1_000, 2)
# ┌─────┬─────┐
# │ n   ┆ y   │
# │ --- ┆ --- │
# │ i64 ┆ i32 │
# ╞═════╪═════╡
# │ 0   ┆ -1  │
# │ 1   ┆ -1  │
# │ …   ┆ …   │
# │ 998 ┆ -1  │
# │ 999 ┆ -1  │
# └─────┴─────┘

from polars.