"http.cookiejar" —— HTTP 客户端的 Cookie 处理
*********************************************

**源代码：** Lib/http/cookiejar.py

======================================================================

"http.cookiejar" 模块定义了用于自动处理 HTTP cookie 的类。这对访问需要
小段数据 —— *cookies* 的网站很有用，这些数据由 Web 服务器的 HTTP 响应
在客户端计算机上设置，然后在以后的 HTTP 请求中返回给服务器。

常规的 Netscape Cookie 协议和 **RFC 2965** 定义的协议都可以处理。RFC
2965 处理默认情况下处于关闭状态。 **RFC 2109** cookie 被解析为
Netscape cookie，随后根据有效的 'policy' 被视为 Netscape 或 RFC 2965
cookie。 请注意，Internet 上的大多数 cookie 是 Netscape cookie。
"http.cookiejar" 尝试遵循事实上的 Netscape cookie 协议（与原始
Netscape 规范中所设定的协议大不相同），包括注意 "max-age" 和 "port"
RFC 2965 引入的 cookie 属性。

注解:

  在 *Set-Cookie* 和 *Set-Cookie2* 头中找到的各种命名参数通常指
  *attributes*。为了不与 Python 属性相混淆，模块文档使用 *cookie-
  attribute* 代替。

此模块定义了以下异常：

exception http.cookiejar.LoadError

   "FileCookieJar" 实例在从文件加载 cookies 出错时抛出这个异常。
   "LoadError" 是 "OSError" 的一个子类。

   在 3.3 版更改: LoadError 成为 "OSError" 的子类而不是 "IOError"。

提供了以下类：

class http.cookiejar.CookieJar(policy=None)

   *policy* 是实现了 "CookiePolicy" 接口的一个对象。

   "CookieJar" 类储存 HTTP cookies。它从 HTTP 请求提取 cookies，并在
   HTTP 响应中返回它们。 "CookieJar" 实例在必要时自动处理包含 cookie
   的到期情况。子类还负责储存和从文件或数据库中查找 cookies。

class http.cookiejar.FileCookieJar(filename, delayload=None, policy=None)

   *policy* 是实现了 "CookiePolicy" 接口的一个对象。对于其他参数，参考
   相应属性的文档。

   一个可以从硬盘中文件加载或保存 cookie 的 "CookieJar"。 Cookies **不
   ** 会在 "load()" 或 "revert()" 方法调用前从命名的文件中加载。子类的
   文档位于段落 FileCookieJar subclasses and co-operation with web
   browsers。

   在 3.8 版更改: 文件名形参支持 *path-like object*。

class http.cookiejar.CookiePolicy

   此类负责确定是否应从服务器接受每个 cookie 或将其返回给服务器。

class http.cookiejar.DefaultCookiePolicy(blocked_domains=None, allowed_domains=None, netscape=True, rfc2965=False, rfc2109_as_netscape=None, hide_cookie2=False, strict_domain=False, strict_rfc2965_unverifiable=True, strict_ns_unverifiable=False, strict_ns_domain=DefaultCookiePolicy.DomainLiberal, strict_ns_set_initial_dollar=False, strict_ns_set_path=False, secure_protocols=("https", "wss"))

   构造参数只能以关键字参数传递，*blocked_domains* 是一个我们既不会接
   受也不会返回 cookie 的域名序列。*allowed_domains* 如果不是 "None"，
   则是仅有的我们会接受或返回的域名序列。*secure_protocols* 是可以添加
   安全 cookies 的协议序列。默认将 *https* 和 *wss* （安全 WebSocket）
   考虑为安全协议。对于其他参数，参考 "CookiePolicy" 和
   "DefaultCookiePolicy" 对象的文档。

   "DefaultCookiePolicy" 实现了 Netscape 和 **RFC 2965** cookies 的标
   准接受 / 拒绝规则。 默认情况下，**RFC 2109** cookies（即在 *Set-
   Cookie* 头中收到的 cookie-attribute 版本为 1 的 cookies ）将按照
   RFC 2965 规则处理。 然而，如果 RFC 2965 的处理被关闭，或者
   "rfc2109_as_netscape" 为 "True"，"Cookie" 实例的 "version" 属性设置
   将被为 0， RFC 2109 cookies "CookieJar" 实例将 "降级" 为 Netscape
   cookies。 "DefaultCookiePolicy" 也提供一些参数以允许一些策略微调。

class http.cookiejar.Cookie

   这个类代表 Netscape、**RFC 2109** 和 **RFC 2965** 的 cookie 。 我们
   不希望 "http.cookiejar" 的用户构建他们自己的 "Cookie" 实例。 相反，
   如果有必要，请在一个  "CookieJar" 实例上调用 "make_cookies()" 。

参见:

  模块 "urllib.request"
     URL 打开带有自动的 cookie 处理。

  模块 "http.cookies"
     HTTP cookie类，主要是对服务端代码有用。  "http.cookiejar" 和
     "http.cookies" 模块不相互依赖。

  https://curl.se/rfc/cookie_spec.html
     原始 Netscape cookie 协议的规范。 虽然这仍然是主流协议，但所有主
     要浏览器（以及 "http.cookiejar" ）实现的 "Netscape cookie协议" 与
     ``cookie_spec.html``中描述的协议仅有几分相似之处。

  **RFC 2109** - HTTP状态管理机制
     被 **RFC 2965** 所取代。使用 *Set-Cookie* version=1 。

  **RFC 2965** - HTTP状态管理机制
     修正了错误的 Netscape 协议。 使用 *Set-Cookie2* 来代替 *Set-
     Cookie* 。 没有广泛被使用。

  http://kristol.org/cookie/errata.html
     未完成的:rfc:*2965* 勘误表。

  HTTP状态管理使用方法


CookieJar 和 FileCookieJar 对象
===============================

"CookieJar" 对象支持 *iterator* 协议，用于迭代包含的 "Cookie" 对象。

"CookieJar" 有以下方法：

CookieJar.add_cookie_header(request)

   在 *request* 中添加正确的 *Cookie* 头。

   如果策略允许（即 "rfc2965" 和 "hide_cookie2" 属性在 "CookieJar" 的
   "CookiePolicy" 实例中分别为 True 和 False ）， *Cookie2* 标头也会在
   适当时候添加。

   如 "urllib.request" 所记载的， *request* 对象（通常是一个
   "urllib.request.Request" 实例）必须支持 "get_full_url()" ,
   "get_host()", "get_type()", "unverifiable()", "has_header()",
   "get_header()", "header_items()", "add_unredirected_header()" 和
   "origin_req_host" 属性。

   在 3.3 版更改: *request* 对象需要 "origin_req_host" 属性。对已废弃
   的方法 "get_origin_req_host()" 的依赖已被移除。

CookieJar.extract_cookies(response, request)

   从HTTP *response* 中提取 cookie，并在政策允许的情况下，将它们存储在
   "CookieJar" 中。

   "CookieJar" 将 在*response* 参数中寻找允许的 *Set-Cookie* 和 *Set-
   Cookie2* 头信息，并适当地存储cookies（须经 "CookiePolicy.set_ok()"
   方法批准）。

   *response* 对象（通常是调用 "urllib.request.urlopen()" 或类似方法的
   结果）应该支持 "info()" 方法，它返回 "email.message.Message" 实例。

   如 "urllib.request" 的文档所说，*request* 对象（通常是一个
   "urllib.request.Request" 实例）必须支持 "get_full_url()",
   "get_host()", "unverifiable()" 和 "origin_req_host" 属性。 该请求用
   于设置 cookie-attributes 的默认值，以及检查 cookie 是否允许被设置。

   在 3.3 版更改: *request* 对象需要 "origin_req_host" 属性。对已废弃
   的方法 "get_origin_req_host()" 的依赖已被移除。

CookieJar.set_policy(policy)

   设置要使用的 "CookiePolicy" 实例。

CookieJar.make_cookies(response, request)

   返回从 *response* 对象中提取的 "Cookie" 对象的序列。

   关于 *response* 和 *request* 参数所需的接口，请参见
   "extract_cookies()" 的文档。

CookieJar.set_cookie_if_ok(cookie, request)

   如果策略规定可以这样做，就设置一个 "Cookie" 。

CookieJar.set_cookie(cookie)

   设置一个 "Cookie"，不需要检查策略是否应该被设置。

CookieJar.clear([domain[, path[, name]]])

   清除一些cookie。

   如果调用时没有参数，则清除所有的cookie。 如果给定一个参数，只有属于
   该 *domain* 的cookies将被删除。如果给定两个参数，那么属于指定的
   *domain* 和 URL *path* 的cookie将被删除。 如果给定三个参数，那么属
   于指定的 *domain* 、*path* 和 *name* 的cookie将被删除

   如果不存在匹配的 cookie，则会引发 "KeyError"。

CookieJar.clear_session_cookies()

   丢弃所有session cookie。

   Discards all contained cookies that have a true "discard" attribute
   (usually because they had either no "max-age" or "expires" cookie-
   attribute, or an explicit "discard" cookie-attribute).  For
   interactive browsers, the end of a session usually corresponds to
   closing the browser window.

   Note that the "save()" method won't save session cookies anyway,
   unless you ask otherwise by passing a true *ignore_discard*
   argument.

"FileCookieJar" implements the following additional methods:

FileCookieJar.save(filename=None, ignore_discard=False, ignore_expires=False)

   Save cookies to a file.

   This base class raises "NotImplementedError".  Subclasses may leave
   this method unimplemented.

   *filename* is the name of file in which to save cookies.  If
   *filename* is not specified, "self.filename" is used (whose default
   is the value passed to the constructor, if any); if "self.filename"
   is "None", "ValueError" is raised.

   *ignore_discard*: save even cookies set to be discarded.
   *ignore_expires*: save even cookies that have expired

   The file is overwritten if it already exists, thus wiping all the
   cookies it contains.  Saved cookies can be restored later using the
   "load()" or "revert()" methods.

FileCookieJar.load(filename=None, ignore_discard=False, ignore_expires=False)

   Load cookies from a file.

   Old cookies are kept unless overwritten by newly loaded ones.

   Arguments are as for "save()".

   The named file must be in the format understood by the class, or
   "LoadError" will be raised.  Also, "OSError" may be raised, for
   example if the file does not exist.

   在 3.3 版更改: 过去触发的 "IOError"，现在是 "OSError" 的别名。

FileCookieJar.revert(filename=None, ignore_discard=False, ignore_expires=False)

   Clear all cookies and reload cookies from a saved file.

   "revert()" can raise the same exceptions as "load()". If there is a
   failure, the object's state will not be altered.

"FileCookieJar" instances have the following public attributes:

FileCookieJar.filename

   Filename of default file in which to keep cookies.  This attribute
   may be assigned to.

FileCookieJar.delayload

   If true, load cookies lazily from disk.  This attribute should not
   be assigned to.  This is only a hint, since this only affects
   performance, not behaviour (unless the cookies on disk are
   changing). A "CookieJar" object may ignore it.  None of the
   "FileCookieJar" classes included in the standard library lazily
   loads cookies.


FileCookieJar subclasses and co-operation with web browsers
===========================================================

The following "CookieJar" subclasses are provided for reading and
writing.

class http.cookiejar.MozillaCookieJar(filename, delayload=None, policy=None)

   A "FileCookieJar" that can load from and save cookies to disk in
   the Mozilla "cookies.txt" file format (which is also used by the
   Lynx and Netscape browsers).

   注解:

     This loses information about **RFC 2965** cookies, and also about
     newer or non-standard cookie-attributes such as "port".

   警告:

     Back up your cookies before saving if you have cookies whose loss
     / corruption would be inconvenient (there are some subtleties
     which may lead to slight changes in the file over a load / save
     round-trip).

   Also note that cookies saved while Mozilla is running will get
   clobbered by Mozilla.

class http.cookiejar.LWPCookieJar(filename, delayload=None, policy=None)

   A "FileCookieJar" that can load from and save cookies to disk in
   format compatible with the libwww-perl library's "Set-Cookie3" file
   format.  This is convenient if you want to store cookies in a
   human-readable file.

   在 3.8 版更改: 文件名形参支持 *path-like object*。


CookiePolicy 对象
=================

Objects implementing the "CookiePolicy" interface have the following
methods:

CookiePolicy.set_ok(cookie, request)

   Return boolean value indicating whether cookie should be accepted
   from server.

   *cookie* is a "Cookie" instance.  *request* is an object
   implementing the interface defined by the documentation for
   "CookieJar.extract_cookies()".

CookiePolicy.return_ok(cookie, request)

   Return boolean value indicating whether cookie should be returned
   to server.

   *cookie* is a "Cookie" instance.  *request* is an object
   implementing the interface defined by the documentation for
   "CookieJar.add_cookie_header()".

CookiePolicy.domain_return_ok(domain, request)

   Return "False" if cookies should not be returned, given cookie
   domain.

   This method is an optimization.  It removes the need for checking
   every cookie with a particular domain (which might involve reading
   many files).  Returning true from "domain_return_ok()" and
   "path_return_ok()" leaves all the work to "return_ok()".

   If "domain_return_ok()" returns true for the cookie domain,
   "path_return_ok()" is called for the cookie path.  Otherwise,
   "path_return_ok()" and "return_ok()" are never called for that
   cookie domain.  If "path_return_ok()" returns true, "return_ok()"
   is called with the "Cookie" object itself for a full check.
   Otherwise, "return_ok()" is never called for that cookie path.

   Note that "domain_return_ok()" is called for every *cookie* domain,
   not just for the *request* domain.  For example, the function might
   be called with both "".example.com"" and ""www.example.com"" if the
   request domain is ""www.example.com"".  The same goes for
   "path_return_ok()".

   The *request* argument is as documented for "return_ok()".

CookiePolicy.path_return_ok(path, request)

   Return "False" if cookies should not be returned, given cookie
   path.

   See the documentation for "domain_return_ok()".

In addition to implementing the methods above, implementations of the
"CookiePolicy" interface must also supply the following attributes,
indicating which protocols should be used, and how.  All of these
attributes may be assigned to.

CookiePolicy.netscape

   Implement Netscape protocol.

CookiePolicy.rfc2965

   Implement **RFC 2965** protocol.

CookiePolicy.hide_cookie2

   Don't add *Cookie2* header to requests (the presence of this header
   indicates to the server that we understand **RFC 2965** cookies).

The most useful way to define a "CookiePolicy" class is by subclassing
from "DefaultCookiePolicy" and overriding some or all of the methods
above.  "CookiePolicy" itself may be used as a 'null policy' to allow
setting and receiving any and all cookies (this is unlikely to be
useful).


DefaultCookiePolicy 对象
========================

Implements the standard rules for accepting and returning cookies.

Both **RFC 2965** and Netscape cookies are covered.  RFC 2965 handling
is switched off by default.

The easiest way to provide your own policy is to override this class
and call its methods in your overridden implementations before adding
your own additional checks:

   import http.cookiejar
   class MyCookiePolicy(http.cookiejar.DefaultCookiePolicy):
       def set_ok(self, cookie, request):
           if not http.cookiejar.DefaultCookiePolicy.set_ok(self, cookie, request):
               return False
           if i_dont_want_to_store_this_cookie(cookie):
               return False
           return True

In addition to the features required to implement the "CookiePolicy"
interface, this class allows you to block and allow domains from
setting and receiving cookies.  There are also some strictness
switches that allow you to tighten up the rather loose Netscape
protocol rules a little bit (at the cost of blocking some benign
cookies).

A domain blacklist and whitelist is provided (both off by default).
Only domains not in the blacklist and present in the whitelist (if the
whitelist is active) participate in cookie setting and returning.  Use
the *blocked_domains* constructor argument, and "blocked_domains()"
and "set_blocked_domains()" methods (and the corresponding argument
and methods for *allowed_domains*).  If you set a whitelist, you can
turn it off again by setting it to "None".

Domains in block or allow lists that do not start with a dot must
equal the cookie domain to be matched.  For example, ""example.com""
matches a blacklist entry of ""example.com"", but ""www.example.com""
does not.  Domains that do start with a dot are matched by more
specific domains too. For example, both ""www.example.com"" and
""www.coyote.example.com"" match "".example.com"" (but ""example.com""
itself does not).  IP addresses are an exception, and must match
exactly.  For example, if blocked_domains contains ""192.168.1.2"" and
"".168.1.2"", 192.168.1.2 is blocked, but 193.168.1.2 is not.

"DefaultCookiePolicy" implements the following additional methods:

DefaultCookiePolicy.blocked_domains()

   Return the sequence of blocked domains (as a tuple).

DefaultCookiePolicy.set_blocked_domains(blocked_domains)

   Set the sequence of blocked domains.

DefaultCookiePolicy.is_blocked(domain)

   Return whether *domain* is on the blacklist for setting or
   receiving cookies.

DefaultCookiePolicy.allowed_domains()

   Return "None", or the sequence of allowed domains (as a tuple).

DefaultCookiePolicy.set_allowed_domains(allowed_domains)

   Set the sequence of allowed domains, or "None".

DefaultCookiePolicy.is_not_allowed(domain)

   Return whether *domain* is not on the whitelist for setting or
   receiving cookies.

"DefaultCookiePolicy" instances have the following attributes, which
are all initialised from the constructor arguments of the same name,
and which may all be assigned to.

DefaultCookiePolicy.rfc2109_as_netscape

   If true, request that the "CookieJar" instance downgrade **RFC
   2109** cookies (ie. cookies received in a *Set-Cookie* header with
   a version cookie-attribute of 1) to Netscape cookies by setting the
   version attribute of the "Cookie" instance to 0.  The default value
   is "None", in which case RFC 2109 cookies are downgraded if and
   only if **RFC 2965** handling is turned off.  Therefore, RFC 2109
   cookies are downgraded by default.

General strictness switches:

DefaultCookiePolicy.strict_domain

   Don't allow sites to set two-component domains with country-code
   top-level domains like ".co.uk", ".gov.uk", ".co.nz".etc.  This is
   far from perfect and isn't guaranteed to work!

**RFC 2965** protocol strictness switches:

DefaultCookiePolicy.strict_rfc2965_unverifiable

   Follow **RFC 2965** rules on unverifiable transactions (usually, an
   unverifiable transaction is one resulting from a redirect or a
   request for an image hosted on another site).  If this is false,
   cookies are *never* blocked on the basis of verifiability

Netscape protocol strictness switches:

DefaultCookiePolicy.strict_ns_unverifiable

   Apply **RFC 2965** rules on unverifiable transactions even to
   Netscape cookies.

DefaultCookiePolicy.strict_ns_domain

   Flags indicating how strict to be with domain-matching rules for
   Netscape cookies.  See below for acceptable values.

DefaultCookiePolicy.strict_ns_set_initial_dollar

   Ignore cookies in Set-Cookie: headers that have names starting with
   "'$'".

DefaultCookiePolicy.strict_ns_set_path

   Don't allow setting cookies whose path doesn't path-match request
   URI.

"strict_ns_domain" is a collection of flags.  Its value is constructed
by or-ing together (for example,
"DomainStrictNoDots|DomainStrictNonDomain" means both flags are set).

DefaultCookiePolicy.DomainStrictNoDots

   When setting cookies, the 'host prefix' must not contain a dot (eg.
   "www.foo.bar.com" can't set a cookie for ".bar.com", because
   "www.foo" contains a dot).

DefaultCookiePolicy.DomainStrictNonDomain

   Cookies that did not explicitly specify a "domain" cookie-attribute
   can only be returned to a domain equal to the domain that set the
   cookie (eg. "spam.example.com" won't be returned cookies from
   "example.com" that had no "domain" cookie-attribute).

DefaultCookiePolicy.DomainRFC2965Match

   When setting cookies, require a full **RFC 2965** domain-match.

The following attributes are provided for convenience, and are the
most useful combinations of the above flags:

DefaultCookiePolicy.DomainLiberal

   Equivalent to 0 (ie. all of the above Netscape domain strictness
   flags switched off).

DefaultCookiePolicy.DomainStrict

   Equivalent to "DomainStrictNoDots|DomainStrictNonDomain".


Cookie 对象
===========

"Cookie" instances have Python attributes roughly corresponding to the
standard cookie-attributes specified in the various cookie standards.
The correspondence is not one-to-one, because there are complicated
rules for assigning default values, because the "max-age" and
"expires" cookie-attributes contain equivalent information, and
because **RFC 2109** cookies may be 'downgraded' by "http.cookiejar"
from version 1 to version 0 (Netscape) cookies.

Assignment to these attributes should not be necessary other than in
rare circumstances in a "CookiePolicy" method.  The class does not
enforce internal consistency, so you should know what you're doing if
you do that.

Cookie.version

   Integer or "None".  Netscape cookies have "version" 0. **RFC 2965**
   and **RFC 2109** cookies have a "version" cookie-attribute of 1.
   However, note that "http.cookiejar" may 'downgrade' RFC 2109
   cookies to Netscape cookies, in which case "version" is 0.

Cookie.name

   Cookie name (a string).

Cookie.value

   Cookie value (a string), or "None".

Cookie.port

   String representing a port or a set of ports (eg. '80', or
   '80,8080'), or "None".

Cookie.path

   Cookie path (a string, eg. "'/acme/rocket_launchers'").

Cookie.secure

   "True" if cookie should only be returned over a secure connection.

Cookie.expires

   Integer expiry date in seconds since epoch, or "None".  See also
   the "is_expired()" method.

Cookie.discard

   "True" if this is a session cookie.

Cookie.comment

   String comment from the server explaining the function of this
   cookie, or "None".

Cookie.comment_url

   URL linking to a comment from the server explaining the function of
   this cookie, or "None".

Cookie.rfc2109

   "True" if this cookie was received as an **RFC 2109** cookie (ie.
   the cookie arrived in a *Set-Cookie* header, and the value of the
   Version cookie-attribute in that header was 1).  This attribute is
   provided because "http.cookiejar" may 'downgrade' RFC 2109 cookies
   to Netscape cookies, in which case "version" is 0.

Cookie.port_specified

   "True" if a port or set of ports was explicitly specified by the
   server (in the *Set-Cookie* / *Set-Cookie2* header).

Cookie.domain_specified

   "True" if a domain was explicitly specified by the server.

Cookie.domain_initial_dot

   "True" if the domain explicitly specified by the server began with
   a dot ("'.'").

Cookies may have additional non-standard cookie-attributes.  These may
be accessed using the following methods:

Cookie.has_nonstandard_attr(name)

   Return "True" if cookie has the named cookie-attribute.

Cookie.get_nonstandard_attr(name, default=None)

   If cookie has the named cookie-attribute, return its value.
   Otherwise, return *default*.

Cookie.set_nonstandard_attr(name, value)

   Set the value of the named cookie-attribute.

The "Cookie" class also defines the following method:

Cookie.is_expired(now=None)

   "True" if cookie has passed the time at which the server requested
   it should expire.  If *now* is given (in seconds since the epoch),
   return whether the cookie has expired at the specified time.


示例
====

The first example shows the most common usage of "http.cookiejar":

   import http.cookiejar, urllib.request
   cj = http.cookiejar.CookieJar()
   opener = urllib.request.build_opener(urllib.request.HTTPCookieProcessor(cj))
   r = opener.open("http://example.com/")

This example illustrates how to open a URL using your Netscape,
Mozilla, or Lynx cookies (assumes Unix/Netscape convention for
location of the cookies file):

   import os, http.cookiejar, urllib.request
   cj = http.cookiejar.MozillaCookieJar()
   cj.load(os.path.join(os.path.expanduser("~"), ".netscape", "cookies.txt"))
   opener = urllib.request.build_opener(urllib.request.HTTPCookieProcessor(cj))
   r = opener.open("http://example.com/")

The next example illustrates the use of "DefaultCookiePolicy". Turn on
**RFC 2965** cookies, be more strict about domains when setting and
returning Netscape cookies, and block some domains from setting
cookies or having them returned:

   import urllib.request
   from http.cookiejar import CookieJar, DefaultCookiePolicy
   policy = DefaultCookiePolicy(
       rfc2965=True, strict_ns_domain=Policy.DomainStrict,
       blocked_domains=["ads.net", ".ads.net"])
   cj = CookieJar(policy)
   opener = urllib.request.build_opener(urllib.request.HTTPCookieProcessor(cj))
   r = opener.open("http://example.com/")
