flytekit.extend.Promise¶

class flytekit.extend.Promise(var, val)[source]¶

This object is a wrapper and exists for three main reasons. Let’s assume we’re dealing with a task like

@task
def t1() -> (int, str): ...

Handling the duality between compilation and local execution - when the task function is run in a local execution mode inside a workflow function, a Python integer and string are produced. When the task is being compiled as part of the workflow, the task call creates a Node instead, and the task returns two Promise objects that point to that Node.
One needs to be able to call
```
x = t1().with_overrides(...)
```
If the task returns an integer or a (int, str) tuple like t1 above, calling with_overrides on the result would throw an error. This Promise object adds that.
Assorted handling for conditionals.

Methods

Parameters:

with_var(new_var)[source]¶

Attributes

attr_path: The attribute path the promise will be resolved with. :rtype: List[Union[str, int]]

is_ready

Returns if the Promise is READY (is not a reference and the val is actually ready)

Usage

p = Promise(...)
...
if p.is_ready():
     print(p.val)
else:
     print(p.ref)

ref: If the promise is NOT READY / Incomplete, then it maps to the origin node that owns the promise

val: If the promise is ready then this holds the actual evaluate value in Flyte’s type system