20.22. "Cookie" — HTTP state management
***************************************

Note: The "Cookie" module has been renamed to "http.cookies" in
  Python 3. The *2to3* tool will automatically adapt imports when
  converting your sources to Python 3.

**Source code:** Lib/Cookie.py

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

The "Cookie" 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").

Note: 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 Cookie.CookieError

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

class Cookie.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 Cookie.SimpleCookie([input])

   This class derives from "BaseCookie" and overrides "value_decode()"
   and "value_encode()" to be the identity and "str()" respectively.

class Cookie.SerialCookie([input])

   This class derives from "BaseCookie" and overrides "value_decode()"
   and "value_encode()" to be the "pickle.loads()" and
   "pickle.dumps()".

   Deprecated since version 2.3: Reading pickled values from untrusted
   cookie data is a huge security hole, as pickle strings can be
   crafted to cause arbitrary code to execute on your server. It is
   supported for backwards compatibility only, and may eventually go
   away.

class Cookie.SmartCookie([input])

   This class derives from "BaseCookie". It overrides "value_decode()"
   to be "pickle.loads()" if it is a valid pickle, and otherwise the
   value itself. It overrides "value_encode()" to be "pickle.dumps()"
   unless it is a string, in which case it returns the value itself.

   Deprecated since version 2.3: The same security warning from
   "SerialCookie" applies here.

A further security note is warranted.  For backwards compatibility,
the "Cookie" module exports a class named "Cookie" which is just an
alias for "SmartCookie".  This is probably a mistake and will likely
be removed in a future version.  You should not use the "Cookie" class
in your applications, for the same reason why you should not use the
"SerialCookie" class.

See also:

  Module "cookielib"
     HTTP cookie handling for web *clients*.  The "cookielib" and
     "Cookie" modules do not depend on each other.

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


20.22.1. Cookie Objects
=======================

BaseCookie.value_decode(val)

   Return a decoded value from a string representation. Return value
   can be any type. This method does nothing in "BaseCookie" — it
   exists so it can be overridden.

BaseCookie.value_encode(val)

   Return an encoded value. *val* can be any type, but return value
   must be a string. This method does nothing 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[, header[, sep]]])

   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).

   Changed in version 2.5: The default separator has been changed from
   "'\n'" to match the cookie specification.

BaseCookie.js_output([attrs])

   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


20.22.2. Morsel Objects
=======================

class Cookie.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"

   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 keys are case-insensitive.

   New in version 2.6: The "httponly" attribute was added.

Morsel.value

   The value of the cookie.

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[, header]])

   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])

   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])

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

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


20.22.3. Example
================

The following example demonstrates how to use the "Cookie" module.

   >>> import Cookie
   >>> C = Cookie.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 = Cookie.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 = Cookie.SimpleCookie()
   >>> C.load("chips=ahoy; vienna=finger") # load from a string (HTTP header)
   >>> print C
   Set-Cookie: chips=ahoy
   Set-Cookie: vienna=finger
   >>> C = Cookie.SimpleCookie()
   >>> C.load('keebler="E=everybody; L=\\"Loves\\"; fudge=\\012;";')
   >>> print C
   Set-Cookie: keebler="E=everybody; L=\"Loves\"; fudge=\012;"
   >>> C = Cookie.SimpleCookie()
   >>> C["oreo"] = "doublestuff"
   >>> C["oreo"]["path"] = "/"
   >>> print C
   Set-Cookie: oreo=doublestuff; Path=/
   >>> C["twix"] = "none for you"
   >>> C["twix"].value
   'none for you'
   >>> C = Cookie.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
   >>> # SerialCookie and SmartCookie are deprecated
   >>> # using it can cause security loopholes in your code.
   >>> C = Cookie.SerialCookie()
   >>> C["number"] = 7
   >>> C["string"] = "seven"
   >>> C["number"].value
   7
   >>> C["string"].value
   'seven'
   >>> print C
   Set-Cookie: number="I7\012."
   Set-Cookie: string="S'seven'\012p1\012."
   >>> C = Cookie.SmartCookie()
   >>> C["number"] = 7
   >>> C["string"] = "seven"
   >>> C["number"].value
   7
   >>> C["string"].value
   'seven'
   >>> print C
   Set-Cookie: number="I7\012."
   Set-Cookie: string=seven
