Function cast

pub fn cast(
    array: &(dyn Array + 'static),
    to_type: &ArrowDataType,
    options: CastOptionsImpl,
) -> Result<Box<dyn Array>, PolarsError>

Expand description

Cast array to the provided data type and return a new Array with type to_type, if possible.

Behavior:

PrimitiveArray to PrimitiveArray: overflowing cast will be None
Boolean to Utf8: true => ‘1’, false => 0
Utf8 to numeric: strings that can’t be parsed to numbers return null, float strings in integer casts return null
Numeric to boolean: 0 returns false, any other value returns true
List to List: the underlying data type is cast
Fixed Size List to List: the underlying data type is cast
List to Fixed Size List: the offsets are checked for valid order, then the underlying type is cast.
Struct to Struct: the underlying fields are cast.
PrimitiveArray to List: a list array with 1 value per slot is created
Date32 and Date64: precision lost when going to higher interval
Time32 and Time64: precision lost when going to higher interval
Timestamp and Date{32|64}: precision lost when going to higher interval
Temporal to/from backing primitive: zero-copy with data type change

Unsupported Casts

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