Inconsistent behavior of `pl.element().replace()`: Works for list of integers, crashes for list of strings

[moritzwilksch]

Inconsistent behavior of `pl.element().replace()`: Works for list of integers, crashes for list of strings

[cmdlineluser]

The int version working seems a bit odd because 4 is being "replaced" by [4]

I did notice that forcing the default value is possible:

df_str.select(
   pl.col("a").list.eval(
      pl.element().replace({"1": ["11", "111"], "2": ["22"]}, default=pl.concat_list(pl.element()))
   )
)

# shape: (1, 1)
# ┌────────────────────────────────┐
# │ a                              │
# │ ---                            │
# │ list[list[str]]                │
# ╞════════════════════════════════╡
# │ [["11", "111"], ["22"], ["4"]] │
# └────────────────────────────────┘

[moritzwilksch]

ahh i figured that happens to force a consistent datatype. Neat workaround with the default though!

[ThomasMAhern]

I too am hoping for this to be resolved!

[cmdlineluser]

@ThomasMAhern What do you need resolved?

It seems that both examples should raise here and the fact that the int case works is a "bug"?

EDIT: Ah, the return_dtype docs say: "the data type is determined automatically based on the other inputs" - so perhaps I am mistaken.

---

Just experimenting further, something else seems broken:

df_int.with_columns(
   a1 = pl.col("a").list.eval(pl.element().replace("1", [["a", "b"]]))
)

# shape: (1, 2)
# ┌───────────┬────────────────────────────┐
# │ a         ┆ a1                         │
# │ ---       ┆ ---                        │
# │ list[i64] ┆ list[list[str]]            │
# ╞═══════════╪════════════════════════════╡
# │ [1, 2, 4] ┆ [["a", "b"], ["2"], ["4"]] │
# └───────────┴────────────────────────────┘

1 is being cast to "1" then the replace succeeds?

[ThomasMAhern]

It seems I'm able to get the expected output if I specify return_dtype=pl.List(pl.String)