# 從當(dāng)前request獲取內(nèi)容
request.args
request.forms
request.cookies
... ...

# 獲取當(dāng)前request
request = get_request()
get_request().args

# File: flask/globals.py
from functools import partial
from werkzeug.local import LocalStack, LocalProxy

def _lookup_req_object(name):
??? top = _request_ctx_stack.top
??? if top is None:
??????? raise RuntimeError('working outside of request context')
??? return getattr(top, name)

# context locals
_request_ctx_stack = LocalStack()
request = LocalProxy(partial(_lookup_req_object, 'request'))

@implements_bool
class LocalProxy(object):
??? __slots__ = ('__local', '__dict__', '__name__')

??? def __init__(self, local, name=None):
??????? # 這里有一個(gè)點(diǎn)需要注意一下，通過(guò)了__setattr__方法，self的
??????? # "_LocalProxy__local" 屬性被設(shè)置成了local，你可能會(huì)好奇
??????? # 這個(gè)屬性名稱(chēng)為什么這么奇怪，其實(shí)這是因?yàn)镻ython不支持真正的
??????? # Private member，具體可以參見(jiàn)官方文檔：
??????? # http://docs.python.org/2/tutorial/classes.html#private-variables-and-class-local-references
??????? # 在這里你只要把它當(dāng)做 self.__local = local 就可以了 :)
??????? object.__setattr__(self, '_LocalProxy__local', local)
??????? object.__setattr__(self, '__name__', name)

??? def _get_current_object(self):
??????? """
??????? 獲取當(dāng)前被代理的真正對(duì)象，一般情況下不會(huì)主動(dòng)調(diào)用這個(gè)方法，除非你因?yàn)?
??????? 某些性能原因需要獲取做這個(gè)被代理的真正對(duì)象，或者你需要把它用來(lái)另外的
??????? 地方。
??????? """
??????? # 這里主要是判斷代理的對(duì)象是不是一個(gè)werkzeug的Local對(duì)象，在我們分析request
??????? # 的過(guò)程中，不會(huì)用到這塊邏輯。
??????? if not hasattr(self.__local, '__release_local__'):
??????????? # 從LocalProxy(partial(_lookup_req_object, 'request'))看來(lái)
??????????? # 通過(guò)調(diào)用self.__local()方法，我們得到了 partial(_lookup_req_object, 'request')()
??????????? # 也就是 ``_request_ctx_stack.top.request``
??????????? return self.__local()
??????? try:
??????????? return getattr(self.__local, self.__name__)
??????? except AttributeError:
??????????? raise RuntimeError('no object bound to %s' % self.__name__)

??? # 接下來(lái)就是一大段一段的Python的魔法方法了，Local Proxy重載了(幾乎)?所有Python
??? # 內(nèi)建魔法方法，讓所有的關(guān)于他自己的operations都指向到了_get_current_object()
??? # 所返回的對(duì)象，也就是真正的被代理對(duì)象。

??? ... ...
??? __setattr__ = lambda x, n, v: setattr(x._get_current_object(), n, v)
??? __delattr__ = lambda x, n: delattr(x._get_current_object(), n)
??? __str__ = lambda x: str(x._get_current_object())
??? __lt__ = lambda x, o: x._get_current_object() < o
??? __le__ = lambda x, o: x._get_current_object() <= o
??? __eq__ = lambda x, o: x._get_current_object() == o
??? __ne__ = lambda x, o: x._get_current_object() != o
??? __gt__ = lambda x, o: x._get_current_object() > o
??? __ge__ = lambda x, o: x._get_current_object() >= o
??? ... ...

def _lookup_req_object(name):
??? top = _request_ctx_stack.top
??? if top is None:
??????? raise RuntimeError('working outside of request context')
??? return getattr(top, name)

# context locals
_request_ctx_stack = LocalStack()
request = LocalProxy(partial(_lookup_req_object, 'request'))

??? def __init__(self):
??????? # 其實(shí)LocalStack主要還是用到了另外一個(gè)Local類(lèi)
??????? # 它的一些關(guān)鍵的方法也被代理到了這個(gè)Local類(lèi)上
??????? # 相對(duì)于Local類(lèi)來(lái)說(shuō)，它多實(shí)現(xiàn)了一些和堆棧“Stack”相關(guān)方法，比如push、pop之類(lèi)
??????? # 所以，我們只要直接看Local代碼就可以
??????? self._local = Local()

??? ... ...

??? @property
??? def top(self):
??????? """
??????? 返回堆棧頂部的對(duì)象
??????? """
??????? try:
??????????? return self._local.stack[-1]
??????? except (AttributeError, IndexError):
??????????? return None

# 所以，當(dāng)我們調(diào)用_request_ctx_stack.top時(shí)，其實(shí)是調(diào)用了 _request_ctx_stack._local.stack[-1]
# 讓我們來(lái)看看Local類(lèi)是怎么實(shí)現(xiàn)的吧，不過(guò)在這之前我們得先看一下下面出現(xiàn)的get_ident方法

# 首先嘗試著從greenlet導(dǎo)入getcurrent方法，這是因?yàn)槿绻鹒lask跑在了像gevent這種容器下的時(shí)候
# 所以的請(qǐng)求都是以greenlet作為最小單位，而不是thread線(xiàn)程。
try:
??? from greenlet import getcurrent as get_ident
except ImportError:
??? try:
??????? from thread import get_ident
??? except ImportError:
??????? from _thread import get_ident

# 總之，這個(gè)get_ident方法將會(huì)返回當(dāng)前的協(xié)程/線(xiàn)程ID，這對(duì)于每一個(gè)請(qǐng)求都是唯一的

class Local(object):
??? __slots__ = ('__storage__', '__ident_func__')

??? def __init__(self):
??????? object.__setattr__(self, '__storage__', {})
??????? object.__setattr__(self, '__ident_func__', get_ident)

??? ... ...

??? # 問(wèn)題的關(guān)鍵就在于Local類(lèi)重載了__getattr__和__setattr__這兩個(gè)魔法方法

??? def __getattr__(self, name):
??????? try:
??????????? # 在這里我們返回調(diào)用了self.__ident_func__()，也就是當(dāng)前的唯一ID
??????????? # 來(lái)作為_(kāi)_storage__的key
??????????? return self.__storage__[self.__ident_func__()][name]
??????? except KeyError:
??????????? raise AttributeError(name)

??? def __setattr__(self, name, value):
??????? ident = self.__ident_func__()
??????? storage = self.__storage__
??????? try:
??????????? storage[ident][name] = value
??????? except KeyError:
??????????? storage[ident] = {name: value}

??? ... ...

??? # 重載了這兩個(gè)魔法方法之后

??? # Local().some_value 不再是它看上去那么簡(jiǎn)單了:
??? # 首先我們先調(diào)用get_ident方法來(lái)獲取當(dāng)前運(yùn)行的線(xiàn)程/協(xié)程ID
??? # 然后獲取這個(gè)ID空間下的some_value屬性，就像這樣：
??? #
??? #?? Local().some_value -> Local()[current_thread_id()].some_value
??? #
??? # 設(shè)置屬性的時(shí)候也是這個(gè)道理