When working with s3fs (For AWS S3), it still raises "Polars found a filename" warning

[MacHu-GWU]

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

import polars as pl
import s3fs

df = pl.DataFrame({
    "foo": ["a", "b", "c", "d", "d"],
    "bar": [1, 2, 3, 4, 5],
})

fs = s3fs.S3FileSystem()
destination = "s3://bucket/my_file.parquet"

# write parquet
with fs.open(destination, mode='wb') as f:
    df.write_parquet(f)

Log output

/Users/sanhehu/Documents/GitHub/polars_aws-project/polars_aws/s3/_write_parquet.py:56: UserWarning: Polars found a filename. Ensure you pass a path to the file instead of a python file object when possible for best performance.
    df.write_parquet(f, **kwargs)

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html

Issue description

I am following the code in https://docs.pola.rs/user-guide/io/cloud-storage/#writing-to-cloud-storage, how ever, it still raises the "UserWarning: Polars found a filename. Ensure you pass a path to the file instead of a python file object when possible for best performance." warning. I guess it's because the example doesn't match the polars recommended best practice.

Expected behavior

Should not have warning

Installed versions

--------Version info---------
Polars:               1.4.0
Index type:           UInt32
Platform:             macOS-14.3-arm64-arm-64bit
Python:               3.10.10 (main, Feb 20 2024, 22:22:03) [Clang 15.0.0 (clang-1500.1.0.2.5)]

----Optional dependencies----
adbc_driver_manager:  <not installed>
cloudpickle:          <not installed>
connectorx:           <not installed>
deltalake:            <not installed>
fastexcel:            <not installed>
fsspec:               2024.6.1
gevent:               <not installed>
great_tables:         <not installed>
hvplot:               <not installed>
matplotlib:           <not installed>
nest_asyncio:         <not installed>
numpy:                <not installed>
openpyxl:             <not installed>
pandas:               <not installed>
pyarrow:              <not installed>
pydantic:             <not installed>
pyiceberg:            <not installed>
sqlalchemy:           <not installed>
torch:                <not installed>
xlsx2csv:             <not installed>
xlsxwriter:           <not installed>

[deanm0000]

I'm not sure if gcs and s3 open file objects have fs attribute but files opened with adlfs have fs. If the other two do then I think we can just add a check here

polars/py-polars/src/file.rs

Lines 267 to 271 in fd00ee6

	if !py_f.is_exact_instance(&io.getattr("BytesIO").unwrap()) {
	polars_warn!("Polars found a filename. \
	Ensure you pass a path to the file instead of a python file object when possible for best \
	performance.");
	}

so in addition to skipping the warning for BytesIO also skip the warning if py_f.hasattr('fs').

[WillAgeG]

And how to solve the problem?

[breanna-gream]

Any update on this issue? I am also seeing this warning message when using gcsfs for Google Cloud Storage

[nameexhaustion]

I would recommend to try using write_parquet() to the S3 URL directly, as support for this was added in the latest release.