Struct ReadAs 

pub struct ReadAs {
    pub delimiter: Option<u8>,
    pub has_header: Option<bool>,
    pub skip_rows: Option<usize>,
    pub skip_lines: Option<usize>,
    pub infer_schema_length: Option<usize>,
    pub ignore_errors: bool,
    pub try_parse_dates: bool,
    pub comment_char: Option<String>,
    pub header_rows: Vec<usize>,
    pub header_join: String,
}

The few reader settings that change what a sample of a file’s columns comes back as.

The sample exists to say what the open will do, so it reads each file the way the open will. Guessing instead, and then standing down wherever the guess might be wrong, does not work: OpenOptions::from_args_and_config fills in infer_schema_length and parse_strings on every run with no flags at all, so a predicate over “did the user set anything” is true every time and the sample never runs. That shipped once — the notes about how a directory was stacked never appeared outside the tests, which built OpenOptions::default() and saw None in both.

Default is what Polars’ own readers do, which is what the home screen’s opens pass.

Fields

delimiter: Option<u8>

has_header: Option<bool>

skip_rows: Option<usize>

skip_lines: Option<usize>

infer_schema_length: Option<usize>

ignore_errors: bool

try_parse_dates: bool

comment_char: Option<String>

header_rows: Vec<usize>

header_join: String

Trait Implementations

impl Clone for ReadAs

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ReadAs

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for ReadAs

fn default() -> Self

What a directory opened from the home screen is read with: OpenOptions::default() plus hive, whose csv_try_parse_dates() is true because parse_strings is unset there.

Written out rather than derived. A derived Default gives try_parse_dates: false, which is not what any caller wants and differs from what the read does — two defaults for one thing, and the wrong one reachable by anybody typing ReadAs::default().