LocalStack--线程隔离的栈结构
Werkzeug 通过自定义 werkzeug.local.Local 类实现线程隔离的栈结构, 封装了push, pop, 和top方法.可以将对象推入、弹出，也可以快速拿到栈顶对象. 同样具有线程隔离的作用. 并没有直接使用threading.Local .
- LocalStack作为栈结构的特性
栈是一种先进后出的基本数据结构.
from werkzeug.local import LocalStack
s = LocalStack()
s.push(1)
print(s.top)
print(s.top) # 获取栈顶元素
print(s.pop()) # 弹出栈顶元素
print(s.top) # 弹出的栈顶元素会删除
s.push(1)
s.push(2)
print(s.top)
print(s.top)
print(s.pop())
print(s.pop())
- 作为线程隔离的特性
线程隔离的作用是: 使当前对象可以正确的使用自己创建的对象, 而不会使用和破坏其他进程的对象.
my_stack = LocalStack()
my_stack.push(2)
print('in main thread after push , value is ', my_stack.top)
def my_work():
print('in new thread before, value is ', my_stack.top)
my_stack.push(3)
print('after new thread after push, value is ', my_stack.top)
new_thread = threading.Thread(target=my_work, name='my_work_thread')
new_thread.start()
time.sleep(1)
print('finally, in new thread , value is', my_stack.top)
打印结果为:
in main thread after push , value is 2
in new thread before, value is None
after new thread after push, value is 3
finally, in new thread , value is 2
源代码
class Local(object):
__slots__ = ('__storage__', '__ident_func__')
def __init__(self):
object.__setattr__(self, '__storage__', {})
object.__setattr__(self, '__ident_func__', get_ident)
...
def __setattr__(self, name, value):
ident = self.__ident_func__()
storage = self.__storage__
try:
storage[ident][name] = value
except KeyError:
storage[ident] = {name: value}
__slots__限制了Local类只可以有两个属性：__storage__和__ident_func__。从构造函，__storage__是一个字典，而__ident_func__是一个函数，用来识别当前线程或协程.