request中之自定义的结构体

# 通过LookupDict构建个可以根据多个value查找key的字典
class LookupDict(dict):
    """Dictionary lookup object."""

    def __init__(self, name=None):
        self.name = name
        super(LookupDict, self).__init__()

    def __repr__(self):
        return '<lookup \'%s\'>' % (self.name)

    def __getitem__(self, key):
        # We allow fall-through here, so values default to None

        return self.__dict__.get(key, None)

    def get(self, key, default=None):
        return self.__dict__.get(key, default)


In [2]: _codes = {
   ...: 
   ...:     # Informational.
   ...:     100: ('continue',),
   ...:     101: ('switching_protocols',),
   ...:     102: ('processing',),
   ...:     103: ('checkpoint',),
   ...:     122: ('uri_too_long', 'request_uri_too_long')
   ...: }

In [3]: codes = LookupDict(name='status_codes')

In [4]: for code, titles in _codes.items():
   ...:     for title in titles:
   ...:         setattr(codes, title, code)
   ...:         if not title.startswith('\\'):
   ...:             setattr(codes, title.upper(), code)
   ...:             

In [5]: codes
Out[5]: <lookup 'status_codes'>

In [6]: codes.processing
Out[6]: 102

In [7]: codes.checkpoint
Out[7]: 103

# codes的__dict__如下
In [8]: codes.__dict__
Out[8]: 
{'CHECKPOINT': 103,
 'CONTINUE': 100,
 'PROCESSING': 102,
 'REQUEST_URI_TOO_LONG': 122,
 'SWITCHING_PROTOCOLS': 101,
 'URI_TOO_LONG': 122,
 'checkpoint': 103,
 'continue': 100,
 'name': 'status_codes',
 'processing': 102,
 'request_uri_too_long': 122,
 'switching_protocols': 101,
 'uri_too_long': 122}

---

# CaseInsensitiveDict定义了大小不敏感的字典
class CaseInsensitiveDict(collections.MutableMapping):
    """
        cid = CaseInsensitiveDict()
        cid['Accept'] = 'application/json'
        cid['aCCEPT'] == 'application/json'  # True
        list(cid) == ['Accept']  # True"""

    def __init__(self, data=None, **kwargs):
        self._store = OrderedDict()
        if data is None:
            data = {}
        self.update(data, **kwargs)

    def __setitem__(self, key, value):
        # Use the lowercased key for lookups, but store the actual
        # key alongside the value.
        self._store[key.lower()] = (key, value)

    def __getitem__(self, key):
        return self._store[key.lower()][1]

    def __delitem__(self, key):
        del self._store[key.lower()]

    def __iter__(self):
        return (casedkey for casedkey, mappedvalue in self._store.values())

    def __len__(self):
        return len(self._store)

    def lower_items(self):
        """Like iteritems(), but with all lowercase keys."""
        return (
            (lowerkey, keyval[1])
            for (lowerkey, keyval)
            in self._store.items()
        )

    def __eq__(self, other):
        if isinstance(other, collections.Mapping):
            other = CaseInsensitiveDict(other)
        else:
            return NotImplemented
        # Compare insensitively
        return dict(self.lower_items()) == dict(other.lower_items())

    # Copy is required
    def copy(self):
        return CaseInsensitiveDict(self._store.values())

    def __repr__(self):
        return str(dict(self.items()))


MutableMapping的定义是实现__getitem__,__setitem__,__delitem__,__iter__,__len__方法的对象。
CaseInsensitiveDict通过将key转换为小写进行查找，在字典值中以元组的形式存储了原始键和值。
lower_items()返回小写的key,和原始的value。

In [13]: cid = CaseInsensitiveDict()

In [16]: cid
Out[16]: {'Accept': 'application/json'}

In [19]: cid.__dict__
Out[19]: {'_store': OrderedDict([('accept', ('aCCEPT', 'application/json'))])}

In [30]: list(cid.lower_items())
Out[30]: [('accept', 'application/json'), ('ab', 'Cd')]

In [31]: cid._store.items()
Out[31]: odict_items([('accept', ('aCCEPT', 'application/json')), ('ab', ('Ab', 'Cd'))])