"http.cookies" --- HTTP状态管理
*******************************

**源代码:** Lib/http/cookies.py

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

The "http.cookies" module defines classes for abstracting the concept
of cookies, an HTTP state management mechanism. It supports both
simple string-only cookies, and provides an abstraction for having any
serializable data-type as cookie value.

The module formerly strictly applied the parsing rules described in
the **RFC 2109** and **RFC 2068** specifications.  It has since been
discovered that MSIE 3.0x doesn't follow the character rules outlined
in those specs and also many current day browsers and servers have
relaxed parsing rules when comes to Cookie handling.  As a result, the
parsing rules used are a bit less strict.

The character set, "string.ascii_letters", "string.digits" and
"!#$%&'*+-.^_`|~:" denote the set of valid characters allowed by this
module in Cookie name (as "key").

在 3.3 版更改: Allowed ':' as a valid Cookie name character.

注解:

  On encountering an invalid cookie, "CookieError" is raised, so if
  your cookie data comes from a browser you should always prepare for
  invalid data and catch "CookieError" on parsing.

exception http.cookies.CookieError

   Exception failing because of **RFC 2109** invalidity: incorrect
   attributes, incorrect *Set-Cookie* header, etc.

class http.cookies.BaseCookie([input])

   This class is a dictionary-like object whose keys are strings and
   whose values are "Morsel" instances. Note that upon setting a key
   to a value, the value is first converted to a "Morsel" containing
   the key and the value.

   If *input* is given, it is passed to the "load()" method.

class http.cookies.SimpleCookie([input])

   This class derives from "BaseCookie" and overrides "value_decode()"
   and "value_encode()". SimpleCookie supports strings as cookie
   values. When setting the value, SimpleCookie calls the builtin
   "str()" to convert the value to a string. Values received from HTTP
   are kept as strings.

参见:

  Module "http.cookiejar"
     HTTP cookie handling for web *clients*.  The "http.cookiejar" and
     "http.cookies" modules do not depend on each other.

  **RFC 2109** - HTTP State Management Mechanism
     This is the state management specification implemented by this
     module.


Cookie 对象
===========

BaseCookie.value_decode(val)

   Return a tuple "(real_value, coded_value)" from a string
   representation. "real_value" can be any type. This method does no
   decoding in "BaseCookie" --- it exists so it can be overridden.

BaseCookie.value_encode(val)

   Return a tuple "(real_value, coded_value)". *val* can be any type,
   but "coded_value" will always be converted to a string. This method
   does no encoding in "BaseCookie" --- it exists so it can be
   overridden.

   In general, it should be the case that "value_encode()" and
   "value_decode()" are inverses on the range of *value_decode*.

BaseCookie.output(attrs=None, header='Set-Cookie:', sep='\r\n')

   Return a string representation suitable to be sent as HTTP headers.
   *attrs* and *header* are sent to each "Morsel"'s "output()" method.
   *sep* is used to join the headers together, and is by default the
   combination "'\r\n'" (CRLF).

BaseCookie.js_output(attrs=None)

   Return an embeddable JavaScript snippet, which, if run on a browser
   which supports JavaScript, will act the same as if the HTTP headers
   was sent.

   The meaning for *attrs* is the same as in "output()".

BaseCookie.load(rawdata)

   If *rawdata* is a string, parse it as an "HTTP_COOKIE" and add the
   values found there as "Morsel"s. If it is a dictionary, it is
   equivalent to:

      for k, v in rawdata.items():
          cookie[k] = v


Morsel 对象
===========

class http.cookies.Morsel

   Abstract a key/value pair, which has some **RFC 2109** attributes.

   Morsels are dictionary-like objects, whose set of keys is constant
   --- the valid **RFC 2109** attributes, which are

   * "expires"

   * "path"

   * "comment"

   * "domain"

   * "max-age"

   * "secure"

   * "version"

   * "httponly"

   * "samesite"

   The attribute "httponly" specifies that the cookie is only
   transferred in HTTP requests, and is not accessible through
   JavaScript. This is intended to mitigate some forms of cross-site
   scripting.

   The attribute "samesite" specifies that the browser is not allowed
   to send the cookie along with cross-site requests. This helps to
   mitigate CSRF attacks. Valid values for this attribute are "Strict"
   and "Lax".

   The keys are case-insensitive and their default value is "''".

   在 3.5 版更改: "__eq__()" now takes "key" and "value" into account.

   在 3.7 版更改: Attributes "key", "value" and "coded_value" are
   read-only.  Use "set()" for setting them.

   在 3.8 版更改: Added support for the "samesite" attribute.

Morsel.value

   Cookie的值。

Morsel.coded_value

   The encoded value of the cookie --- this is what should be sent.

Morsel.key

   The name of the cookie.

Morsel.set(key, value, coded_value)

   Set the *key*, *value* and *coded_value* attributes.

Morsel.isReservedKey(K)

   Whether *K* is a member of the set of keys of a "Morsel".

Morsel.output(attrs=None, header='Set-Cookie:')

   Return a string representation of the Morsel, suitable to be sent
   as an HTTP header. By default, all the attributes are included,
   unless *attrs* is given, in which case it should be a list of
   attributes to use. *header* is by default ""Set-Cookie:"".

Morsel.js_output(attrs=None)

   Return an embeddable JavaScript snippet, which, if run on a browser
   which supports JavaScript, will act the same as if the HTTP header
   was sent.

   The meaning for *attrs* is the same as in "output()".

Morsel.OutputString(attrs=None)

   Return a string representing the Morsel, without any surrounding
   HTTP or JavaScript.

   The meaning for *attrs* is the same as in "output()".

Morsel.update(values)

   Update the values in the Morsel dictionary with the values in the
   dictionary *values*.  Raise an error if any of the keys in the
   *values* dict is not a valid **RFC 2109** attribute.

   在 3.5 版更改: an error is raised for invalid keys.

Morsel.copy(value)

   Return a shallow copy of the Morsel object.

   在 3.5 版更改: return a Morsel object instead of a dict.

Morsel.setdefault(key, value=None)

   Raise an error if key is not a valid **RFC 2109** attribute,
   otherwise behave the same as "dict.setdefault()".


示例
====

The following example demonstrates how to use the "http.cookies"
module.

   >>> from http import cookies
   >>> C = cookies.SimpleCookie()
   >>> C["fig"] = "newton"
   >>> C["sugar"] = "wafer"
   >>> print(C) # generate HTTP headers
   Set-Cookie: fig=newton
   Set-Cookie: sugar=wafer
   >>> print(C.output()) # same thing
   Set-Cookie: fig=newton
   Set-Cookie: sugar=wafer
   >>> C = cookies.SimpleCookie()
   >>> C["rocky"] = "road"
   >>> C["rocky"]["path"] = "/cookie"
   >>> print(C.output(header="Cookie:"))
   Cookie: rocky=road; Path=/cookie
   >>> print(C.output(attrs=[], header="Cookie:"))
   Cookie: rocky=road
   >>> C = cookies.SimpleCookie()
   >>> C.load("chips=ahoy; vienna=finger") # load from a string (HTTP header)
   >>> print(C)
   Set-Cookie: chips=ahoy
   Set-Cookie: vienna=finger
   >>> C = cookies.SimpleCookie()
   >>> C.load('keebler="E=everybody; L=\\"Loves\\"; fudge=\\012;";')
   >>> print(C)
   Set-Cookie: keebler="E=everybody; L=\"Loves\"; fudge=\012;"
   >>> C = cookies.SimpleCookie()
   >>> C["oreo"] = "doublestuff"
   >>> C["oreo"]["path"] = "/"
   >>> print(C)
   Set-Cookie: oreo=doublestuff; Path=/
   >>> C = cookies.SimpleCookie()
   >>> C["twix"] = "none for you"
   >>> C["twix"].value
   'none for you'
   >>> C = cookies.SimpleCookie()
   >>> C["number"] = 7 # equivalent to C["number"] = str(7)
   >>> C["string"] = "seven"
   >>> C["number"].value
   '7'
   >>> C["string"].value
   'seven'
   >>> print(C)
   Set-Cookie: number=7
   Set-Cookie: string=seven
