Cookie — HTTP state management

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).

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.

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 Morsels. If it is a dictionary, it is equivalent to:

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

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().

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