Zone tasks

node-graph supports a context-manager style for building graphs inline. The context-manager style also exposes zones such as If and While and a shared ctx object for passing values between tasks.

Zones: If and While

Zones allow you to gate or repeat a block of tasks based on a condition. The condition itself is defined by a task result.

ctx is a shared store for intermediate values. You can write to it from one task and read it as input in another task.

from node_graph import task
from node_graph import If, While, get_current_graph


@task()
def smaller_than(x, y):
    return x < y


@task()
def add(x, y):
    return x + y


@task()
def is_even(x):
    return x % 2 == 0


@task.graph()
def while_with_if(index=0, limit=10, total=0, increment=1):
    graph = get_current_graph()
    graph.ctx.total = total
    graph.ctx.index = index
    condition = smaller_than(graph.ctx.index, limit).result

    with While(condition):
        is_even_cond = is_even(graph.ctx.index).result
        with If(is_even_cond) as if_zone:
            graph.ctx.total = add(
                x=graph.ctx.total,
                y=graph.ctx.index,
            ).result
        next_index = add(x=graph.ctx.index, y=increment).result
        graph.ctx.index = next_index
        if_zone >> next_index

    return graph.ctx.total


g = while_with_if.build(index=0, limit=10, total=0, increment=1)
g

If and While are available for both context-manager graphs and @task.graph workflows.