为什么 Sequence 是 mypy 中不支持的 + 操作数类型? [英] Why is Sequence an unsupported operand type for + in mypy?

问题描述

mypy 给出的错误是 Sequence[str] 不是 + 运算符支持的操作数类型:

mypy is giving an error that Sequence[str] is not a supported operand type for the + operator:

# test.py

from typing import Sequence


def test(x: Sequence[str], y: Sequence[str]) -> Sequence[str]:
    return x + y

$ mypy test.py
test.py:5: error: Unsupported left operand type for + ("Sequence[str]")
Found 1 error in 1 file (checked 1 source file)

pytype 给出了类似的错误:

pytype gives a similar error:

$ pytype test.py 

[...]

  No attribute '__add__' on Sequence[str] or '__radd__' on Sequence[str]

[...]

为什么 Sequence[str] 是 + 不支持的操作数类型?

Why is Sequence[str] an unsupported operand type for +?

推荐答案

根据文档，序列不一定实现 __add__:

According to the doc, sequences do not necessarily implement __add__:

https://docs.python.org/3/glossary.html#term-sequence

不支持连接的 Sequence 示例是 range.

An example of a Sequence that doesn't support concatenation would be a range.

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