LocalStack 对象维护栈
模拟
import threading
"""
storage = {
1232: {stack:[123,456]}
}
"""
class Local(object):
def __init__(self):
object.__setattr__(self, 'storage', {})
def __setattr__(self, key, value):
ident = threading.get_ident() # 1233
if ident in self.storage:
self.storage[ident][key] = value
else:
self.storage[ident] = {key: value}
def __getattr__(self, item):
ident = threading.get_ident()
if ident not in self.storage:
return
if item not in self.storage[ident]:
return
return self.storage[ident][item]
class LocalStack(object):
def __init__(self):
self._local = Local()
def push(self, value):
"""
将值放入栈
:param value:
:return:
"""
re = self._local.stack
if re:
self._local.stack.append(value)
else:
self._local.stack = [value,]
return re
def pop(self,):
"""
从栈中拿走值
:return:
"""
if not self._local.stack:
return
if len(self._local.stack) == 1:
data = self._local.stack.pop()
# 当stack中的元素为1时，执行pop操作后，要销毁stack,这里暂时没有做
return data
else:
return self._local.stack.pop()
def top(self):
"""
查看栈顶的数据
:return:
"""
if not self._local.stack:
return
return self._local.stack[-1]
st = LocalStack()
st.push(123)
st.push(456)
a = st.top()
b = st.pop()
b = st.pop()
# # b = st.pop()
a = st.top()
print(b,a)
源码展示
LocalStack部分
class LocalStack(object):
"""This class works similar to a :class:`Local` but keeps a stack
of objects instead. This is best explained with an example::
>>> ls = LocalStack()
>>> ls.push(42)
>>> ls.top
42
>>> ls.push(23)
>>> ls.top
23
>>> ls.pop()
23
>>> ls.top
42
They can be force released by using a :class:`LocalManager` or with
the :func:`release_local` function but the correct way is to pop the
item from the stack after using. When the stack is empty it will
no longer be bound to the current context (and as such released).
By calling the stack without arguments it returns a proxy that resolves to
the topmost item on the stack.
.. versionadded:: 0.6.1
"""
def __init__(self):
self._local = Local()
def __release_local__(self):
self._local.__release_local__()
def _get__ident_func__(self):
return self._local.__ident_func__
def _set__ident_func__(self, value):
object.__setattr__(self._local, "__ident_func__", value)
__ident_func__ = property(_get__ident_func__, _set__ident_func__)
del _get__ident_func__, _set__ident_func__
def __call__(self):
def _lookup():
rv = self.top
if rv is None:
raise RuntimeError("object unbound")
return rv
return LocalProxy(_lookup)
def push(self, obj):
"""Pushes a new item to the stack"""
rv = getattr(self._local, "stack", None)
if rv is None:
self._local.stack = rv = []
rv.append(obj)
return rv
def pop(self):
"""Removes the topmost item from the stack, will return the
old value or `None` if the stack was already empty.
"""
stack = getattr(self._local, "stack", None)
if stack is None:
return None
elif len(stack) == 1:
release_local(self._local)
return stack[-1]
else:
return stack.pop()
@property
def top(self):
"""The topmost item on the stack. If the stack is empty,
`None` is returned.
"""
try:
return self._local.stack[-1]
except (AttributeError, IndexError):
return None