Incorrect PolarsInefficientMapWarning for string containment with in #17182
Description
Checks
- I have checked that this issue has not already been reported.
- I have confirmed this bug exists on the latest version of Polars.
Reproducible example
string = "qwerty"
substring = "we"
df = pl.DataFrame({"substring": [substring]})
df.select(
pl.col("substring").map_elements(
lambda substring: substring in string,
return_dtype=pl.Boolean,
)
)From discord here
Somewhat related to #14055 as it also reports issues with different operator behaviour based on input types.
If you believe this is too closely related to that issue, feel free to close.
Log output
<ipython-input-40-a1f88d5d4bbb>:7: PolarsInefficientMapWarning:
Expr.map_elements is significantly slower than the native expressions API.
Only use if you absolutely CANNOT implement your logic otherwise.
Replace this expression...
- pl.col("substring").map_elements(lambda substring: ...)
with this one instead:
+ pl.col("substring").is_in(string)Issue description
As part of PolarsInefficientMapWarning, Python's in operator should be translated to Expr.str.contains(...) when the right operand of substring in string is a str
Expected behavior
Provide a correct suggestion as part of the warning. The current suggestion raises an error.
Installed versions
--------Version info---------
Polars: 0.20.31
Index type: UInt32
Platform: Linux-6.1.85+-x86_64-with-glibc2.35
Python: 3.10.12 (main, Nov 20 2023, 15:14:05) [GCC 11.4.0]
----Optional dependencies----
adbc_driver_manager: <not installed>
cloudpickle: 2.2.1
connectorx: <not installed>
deltalake: <not installed>
fastexcel: <not installed>
fsspec: 2023.6.0
gevent: <not installed>
hvplot: <not installed>
matplotlib: 3.7.1
nest_asyncio: 1.6.0
numpy: 1.25.2
openpyxl: 3.1.4
pandas: 2.0.3
pyarrow: 14.0.2
pydantic: 2.7.4
pyiceberg: <not installed>
pyxlsb: <not installed>
sqlalchemy: 2.0.31
torch: 2.3.0+cu121
xlsx2csv: <not installed>
xlsxwriter: <not installed>