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42 lines
No EOL
1 KiB
Markdown
42 lines
No EOL
1 KiB
Markdown
# Spread assignment
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In a decomposing assignment, putting `...` in front of a variable expands all remaining elements into that variable. This is called expansion assignment.
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```python
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[x,...y] = [1, 2, 3]
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assert x == 1
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assert y == [2, 3]
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x, ...y = (1, 2, 3)
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assert x == 1
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assert y == (2, 3)
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```
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## Extract assignment
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If nothing is written after `...`, the remaining elements are ignored and assigned. This type of expansion assignment is specifically called extractive assignment.
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Extraction assignment is a convenient syntax for localizing specific attributes within a module or record.
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```python
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{sin; cos; tan; ..} = import "math"
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```
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After that, you can use `sin, cos, tan` locally.
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You can do the same with records.
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```python
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record = {x = 1; y = 2}
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{x; y; ...} = record
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```
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If you want to expand all, use `{*} = record`. It is `open` in OCaml.
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```python
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record = {x = 1; y = 2}
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{*} = records
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assert x == 1 and y == 2
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```
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<p align='center'>
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<a href='./27_comprehension.md'>Previous</a> | <a href='./29_decorator.md'>Next</a>
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</p> |