利用werkzeug实现线程隔离的全局变量

1. 需求

编码过程中，当函数的调用层级很深时，如果从上层一级级把参数传递进去，往往显得繁琐而且丑陋，所以希望换种方式

2. 目录结构

$ ls
local_var.py test.py

3. 代码

# local_var.py
from werkzeug import Local


_local = Local()


class _Local:
    def __init__(self, key, value):
        self._local = _local
        self._key = key
        self._value = value

    def __enter__(self):
        setattr(self._local, self._key, self._value)

    def __exit__(self, *args):
        delattr(self._local, self._key)


def get_var(name):
    return getattr(_local, name, None)


def exec_with_var(name, value, func, *args, **kwargs):
    with _Local(name, value):
        return func(*args, **kwargs)

# test.py
import local_var


def func():
    value = local_var.get_var('test')
    if value is None:
        print(':bad:', value)
    else:
        print(':good:', value)


if __name__ == "__main__":
    func()
    local_var.exec_with_var('test', 'test-value', func)
    func()

4. 测试

$ python test.py
:bad: None
:good: test-value
:bad: None

5. 参考

• Context Locals