pola-rs/polars · error · AttributeRemovedError

` ` was removed in version 2.0;

Error message

`{name}` was removed in version 2.0; {removed[name]}

What it means

Accessing a function that was removed in polars 2.0 (e.g. `read_csv_batched`, `threadpool_size`, `arctan2d`) raises `AttributeRemovedError` with a replacement hint from a hard-coded `removed` dict in `__getattr__`. The library maps each removed name to a concrete migration instruction and fails immediately so stale call sites are found.

Solutions

1. Follow the per-name hint: use `thread_pool_size`, `scan_csv` with streaming collection, `arctan2` plus `.degrees()`, or group_by with row index.
2. Read the polars 2.0 migration guide and update all removed call sites.
3. Pin polars <2.0 only as a temporary stopgap while migrating.

Example fix

// before
size = polars.threadpool_size()

// after
size = polars.thread_pool_size()

assert not hasattr(polars, 'read_csv_batched'), 'update to scan_csv'

try:
    size = polars.threadpool_size()
except AttributeError:
    size = polars.thread_pool_size()

When it happens

Trigger: Calling `polars.read_csv_batched`, `polars.threadpool_size`, `polars.arctan2d`, or `DataFrame.groups` on polars >= 2.0 (names present in the removed dict).

Common situations: Skipping major-version migration; long-lived internal scripts updated rarely; code relying on renamed APIs like threadpool_size vs thread_pool_size.

Understand the failure class

Background: "is deprecated and will be removed" — deprecation warnings for old API names, keywords, and options, and how to migrate before the removal release — this error's family across 29 libraries.

Related errors

• accessing ` ` from the top-level `polars` module was…
• altair>=5.4.0 is required for `.plot`
• `arctan2` expected a `str` or `Expr` got a
• `arctan2` expected a `str` or `Expr` got a
• arr.dot query vector must be one-dimensional

AI-assisted analysis of pola-rs/polars@fe841f959e (2026-09-18). Data as JSON: /api/errors/b6f2245b572289dd. Report an issue: GitHub.

Appendix: source

Thrown at py-polars/src/polars/__init__.py:554

        import polars.datatypes.group as dtgroup

        if name in dir(dtgroup):
            msg = (
                f"`{name}` was deprecated in version 1.0.0. Define your own data type groups or "
                "use the `polars.selectors` module for selecting columns of a certain data type."
            )
            raise exceptions.AttributeRemovedError(msg)

        # Functions removed in 2.0
        removed = {
            "arctan2d": "use `arctan2` followed by `.degrees()` instead.",
            "groups": "use `df.with_row_index().group_by(...).agg(pl.col('index'))` instead.",
            "read_csv_batched": "use `scan_csv` instead, in conjunction with `LazyFrame.collect(engine='streaming')`.",
            "threadpool_size": "it was renamed; use `thread_pool_size` instead.",
        }
        if name in removed:
            msg = f"`{name}` was removed in version 2.0; {removed[name]}"
            raise exceptions.AttributeRemovedError(msg)

        msg = f"module {__name__!r} has no attribute {name!r}"
        raise AttributeError(msg)

View on GitHub (pinned to fe841f959e)