pola-rs/polars · error · PolarsError

{err}: {path}

Error message

{err}: {path}

What it means

This is the _limit_path_len_io_err wrapper that polars attaches to filesystem errors: it appends the offending path to the underlying io::Error's message ('{err}: {path}'). When the path is longer than 88 characters and POLARS_VERBOSE is unset, the path is truncated to its last 88 characters and a hint to set POLARS_VERBOSE=1 is added. The actual cause is always the wrapped error kind (NotFound, PermissionDenied, IsADirectory, ...).

Source

Thrown at crates/polars-utils/src/io.rs:15

use std::fs::File;
use std::io;
use std::path::Path;

use polars_error::*;

pub fn _limit_path_len_io_err(path: &Path, err: io::Error) -> PolarsError {
    let path = path.to_string_lossy();
    let msg = if path.len() > 88 && !polars_config::config().verbose() {
        let truncated_path: String = path.chars().skip(path.len() - 88).collect();
        format!("{err}: ...{truncated_path} (set POLARS_VERBOSE=1 to see full path)")
    } else {
        format!("{err}: {path}")
    };
    io::Error::new(err.kind(), msg).into()
}

pub fn open_file(path: &Path) -> PolarsResult<File> {
    File::open(path).map_err(|err| _limit_path_len_io_err(path, err))
}

pub fn open_file_write(path: &Path) -> PolarsResult<File> {
    std::fs::OpenOptions::new()
        .write(true)
        .create(true)
        .truncate(true)
        .open(path)
        .map_err(|err| _limit_path_len_io_err(path, err))
}

pub fn create_file(path: &Path) -> PolarsResult<File> {
    File::create(path).map_err(|err| _limit_path_len_io_err(path, err))
}

View on GitHub (pinned to df599052da)

Solutions

1. Read the leading part of the message - it names the real io error; fix that root cause (correct path, create the file, adjust permissions)
2. Set POLARS_VERBOSE=1 so the full untruncated path is printed
3. Resolve relative paths against an explicit base directory before passing them in
4. For long paths, verify every parent directory exists and is traversable

let meta = std::fs::metadata(&path)
    .map_err(|_| format!("path inaccessible: {}", path.display()));
// also check readable: File::open(&path).is_ok()

match pl_result {
    Err(PolarsError::IO(e)) => {
        // message shape: "<io error>: <path or ...last-88-chars>"
        eprintln!("io kind={:?} msg={}", e.kind(), e);
        // rerun with POLARS_VERBOSE=1 to see the full path
    }
    other => other?,
}

When it happens

Trigger: Any local file open/stat failing through polars_utils::io::open_file / open_file_write or cloud path expansion metadata calls - missing file, wrong permissions, a directory where a file was expected - especially with deeply nested paths.

Common situations: Relative paths resolved against an unexpected cwd; permission mismatches in containers; typos; very long paths where the 88-char truncation hides which directory the file is actually in.

Related errors

• expected a file path; {path!r} is a directory
• the `columns` argument should contain a list of all integers
• `columns` arg should only have unique values, got {columns!r
• `fsspec` is required for `storage_options` argument
• empty data from {context}{hint}

AI-assisted analysis of pola-rs/polars@df599052da (2026-08-16). Data as JSON: /api/errors/f8044790adf94803. Report an issue: GitHub.