Expression.cast(to: type) daft.expressions.Expression[source]#

Casts an expression to a given type

Casting defaults to a set of “reasonable behaviors” for each (from_type, to_type) pair. For more fine-grained control, please consult each type’s method accessors or make a feature request for an accessor if none exists for your use-case.

This method supports:

  1. Casting of a PY type to a Primitive type (e.g. converting a PY[object] column of strings to STRING with .cast(str)) - this will coerce each Python object into the specified primitive type, and then convert the data to an optimized backend representation.

  2. Casting between Primitive types, with a set of reasonable default behavior for many type pairs


>>> # [1.0, 2.5, None]: FLOAT -> [1, 2, None]: INTEGER
>>> col("float").cast(int)
>>> # [Path("/tmp1"), Path("/tmp2"), Path("/tmp3")]: PY[Path] -> ["/tmp1", "/tmp1", "/tmp1"]: STRING
>>> col("path_obj_col").cast(str)

Expression with the specified new type

Return type