[Bug]: Enum accepts non-string categories #3338
Description
Describe the bug
In narwhals, Enum does accept non-string inputs but polars doesn't. Spotted in anyschema 🙏🏼
Steps or code to reproduce the bug
This is all good and well
import narwhals as nw
nw.Enum([True, False])
nw.Enum([1, 2])But polars checks and raises:
import polars as pl
pl.Enum([True, False])
# TypeError: Enum categories must be strings; found data of type Boolean
pl.Enum([1, 2])
# TypeError: Enum categories must be strings; found data of type Int64Same for a non-string enum
from enum import Enum
import polars as pl
class Number(Enum):
ONE = 1
TWO = 2
THREE = 3
pl.Enum(Number)
# TypeError: Enum categories must be strings; found data of type Int64Expected results
Raise an exception
Actual results
Passthrough
Please run narwhals.show_versions() and enter the output below.
System:
python: 3.13.9 (main, Oct 14 2025, 13:52:31) [Clang 17.0.0 (clang-1700.0.13.3)]
machine: macOS-15.7.1-arm64-arm-64bit-Mach-O
Python dependencies:
narwhals: 2.12.0
polars: 1.35.2