# Pool.map_prepare()

Stage a map once for repeated runs; return a

Usage

[Source](https://github.com/shikokuchuo/pymizu/blob/main/python/pymizu/__init__.py#L1162-L1209)

``` python
Pool.map_prepare(
    fn,
    x,
    *,
    args=(),
    kwargs=None,
    n_chunks=None,
    seed=None,
    template=None,
    collect=None,
    stream=False,
)
```

[`PreparedMap`](../reference/PreparedMap.md#pymizu.PreparedMap).

Takes the same arguments as [`map()`](../reference/Pool.map.md#pymizu.Pool.map) (minus `timeout`, which is per-run and moves to [PreparedMap.run](../reference/PreparedMap.md#pymizu.PreparedMap.run)). The descriptor pickle, the region create, and the worker-side attach are paid once here; each `pm.run()` re-arms in O(1), reuses the workers' cached contexts, and returns the run's map handle (the collect happens on it). A run collected with `collect="view"` hands its region to the view, so the next run restages into a fresh one. With `stream=True` the staged `x` stays submitter-side, so a replacement `x` of any shape simply re-slices -- only a length change under `template` restages (the output area is sized for the staged length). Close the handle (or use it as a context manager) to unlink the region.