first-python.md

First example (Python)

A Python program that imports durable operations from tcc_engine.primitives and marks exactly one @program async function. There is no context object or workflow wrapper.

The Python frontend treats tcc_engine.primitives and trigora as durable-operations modules. The frontend recognizes resolved imports of program, effect, and wait_for_event. Programs that differ only in that specifier produce the same artifact hash. Aliasing works:

from tcc_engine.primitives import effect as durable_effect

A locally declared def effect is not durable.

from tcc_engine.primitives import program, effect, wait_for_event

@program
async def research():
    result = await effect("generate", generate_something)
    approval = await wait_for_event("approved")
    return {"result": result, "approval": approval}

The effect callback body is not compiled into the artifact. The host supplies the result for key generate. Keys and event names must be string literals. Unsupported constructs are compile errors.

Language semantics: py.subset.v1. Required engine features: ts.control_flow, durable.effect, durable.wait_for_event. Required host capabilities: host.persist_checkpoint, host.effect, host.event. The ts.control_flow feature names the existing instruction set; it is not TypeScript-specific execution.

Walkthrough execution id: first. Locals: result = 0, approval = 1.

Instructions

pc	Instruction
0	LoadConst "generate"
1	Effect
2	StoreLocal 0
3	LoadConst "approved"
4	WaitForEvent
5	StoreLocal 1
6	NewObject
7	LoadLocal 0
8	SetProp "result"
9	LoadLocal 1
10	SetProp "approval"
11	Return

Host sequence, identities, and completed result match the TypeScript first example. Effect idempotency key: first:generate. Wait identity: first:approved::4. With effect generate = 42 and event payload "ok", the result is { result: 42, approval: "ok" }.