如何在 python 3.6 中使用类型提示? [英] How to use type hints in python 3.6?
问题描述
我注意到python 3.5和python 3.6添加了很多关于静态类型检查的功能，所以我尝试了以下代码(在python 3.6，稳定版本中).
I noticed python 3.5 and python 3.6 added a lot of features about static type checking, so I tried with the following code(in python 3.6, stable version).
from typing import List
a: List[str] = []
a.append('a')
a.append(1)
print(a)
令我惊讶的是，python 没有给我错误或警告，尽管 1 被附加到一个应该只包含字符串的 list 中.Pycharm 检测到类型错误并给了我一个警告，但它并不明显并且没有显示在输出控制台中，我担心有时我可能会错过它.我想要以下效果:
What surprised me was that, python didn't give me an error or warning, although 1 was appended to a list which should only contain strings. Pycharm detected the type error and gave me a warning about it, but it was not obvious and it was not shown in the output console, I was afraid sometimes I might miss it. I would like the following effects:
- 如果很明显我使用了如上所示的错误类型，请抛出警告或错误.
- 如果编译器无法可靠地检查我使用的类型是对还是错，请忽略它.
这可能吗?也许 mypy 可以做到，但我更喜欢使用 python-3.6 样式的类型检查(如 a: List[str])而不是注释样式(像 mypy 中使用的 # type List[str]).我很好奇原生python 3.6中是否有一个开关来实现我上面说的两点.
Is that possible? Maybe mypy could do it, but I'd prefer to use python-3.6-style type checking(like a: List[str]) instead of the comment-style(like # type List[str]) used in mypy. And I'm curious if there's a switch in native python 3.6 to achieve the two points I said above.
推荐答案
这可能吗?也许 mypy 可以做到，但我更喜欢使用 Python-3.6 样式的类型检查(如
a: List[str])而不是注释样式(如# type:List[str]) 在 mypy 中使用.我很好奇原生python 3.6中是否有一个开关来实现我上面说的两点.
Is that possible? Maybe mypy could do it, but I'd prefer to use Python-3.6-style type checking (like
a: List[str]) instead of the comment-style (like# type: List[str]) used in mypy. And I'm curious if there's a switch in native python 3.6 to achieve the two points I said above.
Python 不可能为你做这件事；您可以使用 mypy 进行类型检查(PyCharms 内置检查器也应该这样做).除此之外，mypy 也不限制你只能输入注释# type List[str]，你可以使用变量注解作为你在 Python 3.6 中这样做，所以 a: List[str] 工作得同样好.
There's no way Python will do this for you; you can use mypy to get type checking (and PyCharms built-in checker should do it too). In addition to that, mypy also doesn't restrict you to only type comments # type List[str], you can use variable annotations as you do in Python 3.6 so a: List[str] works equally well.
使用 mypy 原样，因为发布是新鲜的，您需要安装 typed_ast 并使用 - 执行 和 mypy-fast-parser--python-version 3.6 如 mypy 的文档中所述.这可能很快就会改变，但现在你需要它们来让它顺利运行
With mypy as is, because the release is fresh, you'll need to install typed_ast and execute mypy with --fast-parser and --python-version 3.6 as documented in mypy's docs. This will probably change soon but for now you'll need them to get it running smoothly
更新: --fast-parser 和 --python-version 3.6 现在不需要了.
Update: --fast-parser and --python-version 3.6 aren't needed now.
在你这样做之后，mypy 检测到你的 a: List[str] 上的第二个操作的不兼容性就好了.假设您的文件名为 tp_check.py 并带有语句:
After you do that, mypy detects the incompatibility of the second operation on your a: List[str] just fine. Let's say your file is called tp_check.py with statements:
from typing import List
a: List[str] = []
a.append('a')
a.append(1)
print(a)
使用上述参数运行 mypy(您必须先 pip install -U typed_ast):
Running mypy with the aforementioned arguments (you must first pip install -U typed_ast):
python -m mypy --fast-parser --python-version 3.6 tp_check.py
捕获错误:
tp_check.py:5: error: Argument 1 to "append" of "list" has incompatible type "int"; expected "str"
正如在使用 Python 进行类型提示的许多其他答案中所述，mypy 和 PyCharms 的类型检查器是执行验证的，不是 Python 本身.Python 目前不使用此信息，它仅将其存储为元数据并在执行过程中忽略它.
As noted in many other answers on type hinting with Python, mypy and PyCharms' type-checkers are the ones performing the validation, not Python itself. Python doesn't use this information currently, it only stores it as metadata and ignores it during execution.
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