"http.cookiejar" --- Cookie handling for HTTP clients
*****************************************************

**Source code:** Lib/http/cookiejar.py

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

The "http.cookiejar" module defines classes for automatic handling of
HTTP cookies.  It is useful for accessing web sites that require small
pieces of data -- *cookies* -- to be set on the client machine by an
HTTP response from a web server, and then returned to the server in
later HTTP requests.

Both the regular Netscape cookie protocol and the protocol defined by
**RFC 2965** are handled.  RFC 2965 handling is switched off by
default. **RFC 2109** cookies are parsed as Netscape cookies and
subsequently treated either as Netscape or RFC 2965 cookies according
to the 'policy' in effect. Note that the great majority of cookies on
the Internet are Netscape cookies. "http.cookiejar" attempts to follow
the de-facto Netscape cookie protocol (which differs substantially
from that set out in the original Netscape specification), including
taking note of the "max-age" and "port" cookie-attributes introduced
with RFC 2965.

備註:

  The various named parameters found in *Set-Cookie* and *Set-Cookie2*
  headers (eg. "domain" and "expires") are conventionally referred to
  as *attributes*.  To distinguish them from Python attributes, the
  documentation for this module uses the term *cookie-attribute*
  instead.

The module defines the following exception:

exception http.cookiejar.LoadError

   Instances of "FileCookieJar" raise this exception on failure to
   load cookies from a file.  "LoadError" is a subclass of "OSError".

   3.3 版更變: LoadError was made a subclass of "OSError" instead of
   "IOError".

The following classes are provided:

class http.cookiejar.CookieJar(policy=None)

   *policy* is an object implementing the "CookiePolicy" interface.

   The "CookieJar" class stores HTTP cookies.  It extracts cookies
   from HTTP requests, and returns them in HTTP responses. "CookieJar"
   instances automatically expire contained cookies when necessary.
   Subclasses are also responsible for storing and retrieving cookies
   from a file or database.

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

   *policy* is an object implementing the "CookiePolicy" interface.
   For the other arguments, see the documentation for the
   corresponding attributes.

   A "CookieJar" which can load cookies from, and perhaps save cookies
   to, a file on disk.  Cookies are **NOT** loaded from the named file
   until either the "load()" or "revert()" method is called.
   Subclasses of this class are documented in section FileCookieJar
   subclasses and co-operation with web browsers.

class http.cookiejar.CookiePolicy

   This class is responsible for deciding whether each cookie should
   be accepted from / returned to the server.

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)

   Constructor arguments should be passed as keyword arguments only.
   *blocked_domains* is a sequence of domain names that we never
   accept cookies from, nor return cookies to. *allowed_domains* if
   not "None", this is a sequence of the only domains for which we
   accept and return cookies.  For all other arguments, see the
   documentation for "CookiePolicy" and "DefaultCookiePolicy" objects.

   "DefaultCookiePolicy" implements the standard accept / reject rules
   for Netscape and **RFC 2965** cookies.  By default, **RFC 2109**
   cookies (ie. cookies received in a *Set-Cookie* header with a
   version cookie-attribute of 1) are treated according to the RFC
   2965 rules.  However, if RFC 2965 handling is turned off or
   "rfc2109_as_netscape" is "True", RFC 2109 cookies are 'downgraded'
   by the "CookieJar" instance to Netscape cookies, by setting the
   "version" attribute of the "Cookie" instance to 0.
   "DefaultCookiePolicy" also provides some parameters to allow some
   fine-tuning of policy.

class http.cookiejar.Cookie

   This class represents Netscape, **RFC 2109** and **RFC 2965**
   cookies.  It is not expected that users of "http.cookiejar"
   construct their own "Cookie" instances.  Instead, if necessary,
   call "make_cookies()" on a "CookieJar" instance.

也參考:

  Module "urllib.request"
     URL opening with automatic cookie handling.

  Module "http.cookies"
     HTTP cookie classes, principally useful for server-side code.
     The "http.cookiejar" and "http.cookies" modules do not depend on
     each other.

  https://curl.haxx.se/rfc/cookie_spec.html
     The specification of the original Netscape cookie protocol.
     Though this is still the dominant protocol, the 'Netscape cookie
     protocol' implemented by all the major browsers (and
     "http.cookiejar") only bears a passing resemblance to the one
     sketched out in "cookie_spec.html".

  **RFC 2109** - HTTP State Management Mechanism
     Obsoleted by **RFC 2965**. Uses *Set-Cookie* with version=1.

  **RFC 2965** - HTTP State Management Mechanism
     The Netscape protocol with the bugs fixed.  Uses *Set-Cookie2* in
     place of *Set-Cookie*.  Not widely used.

  http://kristol.org/cookie/errata.html
     Unfinished errata to **RFC 2965**.

  **RFC 2964** - Use of HTTP State Management


CookieJar and FileCookieJar Objects
===================================

"CookieJar" objects support the *iterator* protocol for iterating over
contained "Cookie" objects.

"CookieJar" has the following methods:

CookieJar.add_cookie_header(request)

   Add correct *Cookie* header to *request*.

   If policy allows (ie. the "rfc2965" and "hide_cookie2" attributes
   of the "CookieJar"'s "CookiePolicy" instance are true and false
   respectively), the *Cookie2* header is also added when appropriate.

   The *request* object (usually a "urllib.request.Request" instance)
   must support the methods "get_full_url()", "get_host()",
   "get_type()", "unverifiable()", "has_header()", "get_header()",
   "header_items()", "add_unredirected_header()" and "origin_req_host"
   attribute as documented by "urllib.request".

   3.3 版更變: *request* object needs "origin_req_host" attribute.
   Dependency on a deprecated method "get_origin_req_host()" has been
   removed.

CookieJar.extract_cookies(response, request)

   Extract cookies from HTTP *response* and store them in the
   "CookieJar", where allowed by policy.

   The "CookieJar" will look for allowable *Set-Cookie* and *Set-
   Cookie2* headers in the *response* argument, and store cookies as
   appropriate (subject to the "CookiePolicy.set_ok()" method's
   approval).

   The *response* object (usually the result of a call to
   "urllib.request.urlopen()", or similar) should support an "info()"
   method, which returns an "email.message.Message" instance.

   The *request* object (usually a "urllib.request.Request" instance)
   must support the methods "get_full_url()", "get_host()",
   "unverifiable()", and "origin_req_host" attribute, as documented by
   "urllib.request".  The request is used to set default values for
   cookie-attributes as well as for checking that the cookie is
   allowed to be set.

   3.3 版更變: *request* object needs "origin_req_host" attribute.
   Dependency on a deprecated method "get_origin_req_host()" has been
   removed.

CookieJar.set_policy(policy)

   Set the "CookiePolicy" instance to be used.

CookieJar.make_cookies(response, request)

   Return sequence of "Cookie" objects extracted from *response*
   object.

   See the documentation for "extract_cookies()" for the interfaces
   required of the *response* and *request* arguments.

CookieJar.set_cookie_if_ok(cookie, request)

   Set a "Cookie" if policy says it's OK to do so.

CookieJar.set_cookie(cookie)

   Set a "Cookie", without checking with policy to see whether or not
   it should be set.

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

   Clear some cookies.

   If invoked without arguments, clear all cookies.  If given a single
   argument, only cookies belonging to that *domain* will be removed.
   If given two arguments, cookies belonging to the specified *domain*
   and URL *path* are removed.  If given three arguments, then the
   cookie with the specified *domain*, *path* and *name* is removed.

   Raises "KeyError" if no matching cookie exists.

CookieJar.clear_session_cookies()

   Discard all session cookies.

   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.

   3.3 版更變: "IOError" used to be raised, it is now an alias of
   "OSError".

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).

   備註:

     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.


CookiePolicy Objects
====================

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 Objects
===========================

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 Objects
==============

"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.


Examples
========

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/")
