输入提示 Python 2

Question

在PEP 484, type hinting was added to Python 3 with the inclusion of the typing模块中。在 Python 2 中有什么办法可以做到这一点吗？我所能想到的就是有一个装饰器来添加到检查类型的方法中，但这会在运行时失败，并且不会像提示允许的那样被更早地捕获。

Answer 1

根据定义类型提示的 PEP 484 中的 Suggested syntax for Python 2.7 and straddling code，有一个与 Python 2.7 兼容的替代语法。然而，它不是强制性的，所以我不知道它的支持程度如何，但引用 PEP：

Some tools may want to support type annotations in code that must be compatible with Python 2.7. For this purpose this PEP has a suggested (but not mandatory) extension where function annotations are placed in a # type: comment. Such a comment must be placed immediately following the function header (before the docstring). An example: the following Python 3 code:
def embezzle(self, account: str, funds: int = 1000000, *fake_receipts: str) -> None:
    """Embezzle funds from account using fake receipts."""
    <code goes here>
is equivalent to the following:
def embezzle(self, account, funds=1000000, *fake_receipts):
    # type: (str, int, *str) -> None
    """Embezzle funds from account using fake receipts."""
    <code goes here>

对于 mypy 支持，请参阅 Type checking Python 2 code。

Answer 2

此时推荐的 python3 兼容方法是遵循 python2 到 3 指南：http://python-future.org/func_annotations.html

def embezzle(self, account: str, funds: int = 1000000, *fake_receipts: str) -> None:
    """Embezzle funds from account using fake receipts."""
    pass

成为：

def embezzle(self, account, funds = 1000000, *fake_receipts):
    """Embezzle funds from account using fake receipts."""
    pass
embezzle.__annotations__ = {'account': str, 'funds': int, 'fake_receipts': str, 'return': None}

Answer 3

这是我编写的一个函数，用于解析 Python 2 类型注释并获取输入类型和 return 类型的元组。使用类型库（Any、Optional、List 等）中的复杂类型定义需要做一些工作：

class InvalidTypeHint(Exception):
    pass    

PYTHON_2_TYPE_HINT_REGEX = "\s*#\s*type:\s*(\(.+\))\s*->\s*(.+)\s*"

def parse_python_2_type_hint(typehint_string):
    # type: (str) -> (tuple, type)
    pattern = re.compile(PYTHON_2_TYPE_HINT_REGEX)
    search_results = pattern.search(typehint_string)
    if not search_results:
        raise InvalidTypeHint('%s does not match type hint spec regex %s' % (typehint_string, PYTHON_2_TYPE_HINT_REGEX))
    arg_types_str = search_results.group(1)
    return_type_str = search_results.group(2)
    try:
        arg_types_tuple = eval(arg_types_str)
        assert isinstance(arg_types_tuple, tuple)
        return_type = eval(return_type_str)
        assert isinstance(return_type, type)
    except Exception as e:
        raise InvalidTypeHint(e)
    return arg_types_tuple, return_type


def parse_arg_types_for_callable(func):
    # type:(callable)->tuple
    """

    :param func:
    :return: list of parameter types if successfully parsed, else None
    """

    # todo make this compatible with python 3 type hints
    # python 2.7 type hint
    source_lines = inspect.getsource(func).split("\n")
    def_statements = 0
    for source_line in source_lines:
        try:
            arg_types_tuple, return_type = parse_python_2_type_hint(source_line)
            return arg_types_tuple
        except InvalidTypeHint:
            if source_line.strip().startswith("def "):
                def_statements += 1
            if def_statements > 1:
                return None

输入提示 Python 2

Type hinting in Python 2

python

python-2.7

types

type-hinting

python-typing