LazyArray

This is an API interface for computing an expression or a Python user defined function.

You can get an object following the LazyArray API with any of the following ways:

• Any expression that involves one or more NDArray objects. e.g. a + b, where a and b are NDArray objects (see this tutorial).

• Using the lazyexpr constructor.

• Using the lazyudf constructor (see a tutorial).

The LazyArray object is a thin wrapper around the expression or user-defined function that allows for lazy computation. This means that the expression is not computed until the compute or __getitem__ methods are called. The compute method will return a new NDArray object with the result of the expression evaluation. The __getitem__ method will return an NumPy object instead.

See the LazyExpr and LazyUDF sections for more information.

Methods

__getitem__	Return a NumPy.ndarray containing the evaluation of the LazyArray.
compute	Return an NDArray containing the evaluation of the LazyArray.
indices	Return an LazyArray containing the indices where self is True.
save	Save the LazyArray on disk.
sort	Return a sorted LazyArray.

LazyExpr

An expression like a + sum(b), where there is at least one NDArray object in operands a and b, returns a LazyExpr object. You can also get a LazyExpr object using the lazyexpr constructor (see below).

This object follows the LazyArray API for computation and storage.

lazyexpr

Get a LazyExpr from an expression.

Utilities

A series of utilities are provided to work with LazyExpr objects.

validate_expr	Validate expression for forbidden syntax and valid method names.
get_expr_operands	Given an expression in string form, return its operands.

LazyUDF

For getting a LazyUDF object (which is LazyArray-compliant) from a user-defined Python function, you can use the lazyudf constructor below. See a tutorial on how this works.

This object follows the LazyArray API for computation, although storage is not supported yet.

lazyudf

Get a LazyUDF from a python user-defined function.