daft.expressions.Expression.apply#

Expression.apply(func: Callable, return_dtype: daft.datatype.DataType) → daft.expressions.expressions.Expression[source]#

Apply a function on each value in a given expression

Note

This is just syntactic sugar on top of a UDF and is convenient to use when your function only operates on a single column, and does not benefit from executing on batches. For either of those other use-cases, use a UDF instead.

Example

>>> def f(x_val: str) -> int:
>>>     return int(x_val) if x_val.isnumeric() else 0
>>>
>>> col("x").apply(f, return_dtype=DataType.int64())
Parameters

  • func – Function to run per value of the expression

  • return_dtype – Return datatype of the function that was ran

Returns

New expression after having run the function on the expression

Return type

Expression