为什么 Python 匹配列表作为元组？

Question

使用Python 3.11.0a2+，以及以下代码：

def my_fun(e):
    match e:
        case (1,):
            print("tuple (1,)")
        case [1]:
            print("list [1]")
        case _:
            print("I don't understand")

使用 my_fun([1]) 调用函数打印“元组 (1,)”。

这种行为是否正确？

如果我明确匹配 tuple((1, )) 而不是 (1,)，它将按预期工作。

如果这不是解释器的错误，那么这种看似奇怪的行为背后的原因是什么？

Answer 1

这是documented under Structural Pattern Matching。

Like unpacking assignments, tuple and list patterns have exactly the same meaning and actually match arbitrary sequences. Technically, the subject must be a sequence. Therefore, an important exception is that patterns don’t match iterators. Also, to prevent a common mistake, sequence patterns don’t match strings.

并在 PEP 635 -- Structural Pattern Matching: Motivation and Rationale

As in iterable unpacking, we do not distinguish between 'tuple' and 'list' notation. [a, b, c], (a, b, c) and a, b, c are all equivalent. While this means we have a redundant notation and checking specifically for lists or tuples requires more effort (e.g. case list([a, b, c])), we mimic iterable unpacking as much as possible.

为什么 Python 匹配列表作为元组？

Why Python matches a list as a tuple?

python

list

tuples

pattern-matching

python-3.10