# 扩展语法

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在分解赋值中，将 `...` 放在变量前面会将所有剩余元素展开到该变量中。这称为展开赋值

```python
[x,...y] = [1, 2, 3]
assert x == 1
assert y == [2, 3]
x, ...y = (1, 2, 3)
assert x == 1
assert y == (2, 3)
```

## 提取赋值

如果在 `...` 之后没有写入任何内容，则忽略并分配剩余的元素。这种类型的赋值具体称为提取赋值
提取分配是一种方便的语法，用于本地化模块或记录中的特定属性

```python
{sin; cos; tan; ..} = import "math"
```


之后，您可以在本地使用`sin，cos，tan`

您可以对记录执行相同的操作。

```python
record = {x = 1; y = 2}
{x; y; ...} = record
```

如果要全部展开，请使用`{*}=record`。它在OCaml中是`open`。

```python
record = {x = 1; y = 2}
{*} = records
assert x == 1 and y == 2
```

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