pola-rs/polars · error · TypeError

`n` parameter of `repeat expected a `int` or `Expr` got a `{

Error message

`n` parameter of `repeat expected a `int` or `Expr` got a `{qualified_type_name(n)}`

What it means

Raised by polars.repeat when the n parameter (after int is auto-wrapped into a literal) is neither an int nor an Expr — detected by the absence of the internal _pyexpr attribute. n must be a Python int or a polars expression so it can be passed to the Rust repeat kernel.

Source

Thrown at py-polars/src/polars/functions/repeat.py:144

            "z"
    ]

    Generate a Series directly by setting `eager=True`.

    >>> pl.repeat(3, n=3, dtype=pl.Int8, eager=True)
    shape: (3,)
    Series: 'repeat' [i8]
    [
            3
            3
            3
    ]
    """
    if isinstance(n, int):
        n = F.lit(n)
    if not hasattr(n, "_pyexpr"):
        msg = f"`n` parameter of `repeat expected a `int` or `Expr` got a `{qualified_type_name(n)}`"
        raise TypeError(msg)
    value_pyexpr = parse_into_expression(value, str_as_lit=True, dtype=dtype)
    expr = wrap_expr(plr.repeat(value_pyexpr, n._pyexpr, dtype))
    if eager:
        return F.select(expr).to_series()
    return expr


@overload
def ones(
    n: int | Expr,
    dtype: PolarsDataType = ...,
    *,
    eager: Literal[False] = ...,
) -> Expr: ...


@overload
def ones(

View on GitHub (pinned to df599052da)

Solutions

1. Coerce to int: n=int(my_count)
2. For per-row repeat lengths use an expression: pl.repeat(value, n=pl.col('len_col'))
3. If n arrives as a Series, use it in an expression context (pl.col) or extract a scalar with int(s[0])

Example fix

// before
pl.repeat(1, n=df['n'])   # Series -> error
// after
pl.repeat(1, n=pl.col('n'))
# scalar case: pl.repeat(1, n=int(count))

import polars as pl

if not isinstance(n, (int, pl.Expr)):
    n = int(n)  # or pl.lit(n) for expressions

from polars import Expr

def is_valid_repeat_n(n) -> bool:
    return isinstance(n, (int, Expr))

try:
    e = pl.repeat(value, n=n)
except TypeError:
    e = pl.repeat(value, n=int(n))

When it happens

Trigger: pl.repeat(0, n=3.0) (float); n=None; n=pl.Series([3]) (Series is not accepted); n coming from a numpy integer or a config value that is not coerced to int.

Common situations: Passing a numpy int64 or a float count from downstream computation; passing a Series of lengths instead of an Expr (e.g. pl.repeat(v, n=df['len']) should be n=pl.col('len')); optional parameters defaulting to None.

Related errors

• expected `by_predicate` to be an expression, got {qualified_
• expected Series in 'arg_where' if 'eager=True', got {type(co
• cannot turn {qualified_type_name(input)!r} into selector
• Cannot pass a dictionary as a single positional argument.\nI
• expected `on` to be str or Expr, got {qualified_type_name(on

AI-assisted analysis of pola-rs/polars@df599052da (2026-08-16). Data as JSON: /api/errors/43a76aaa73894a80. Report an issue: GitHub.