root/django/trunk/django/utils/datastructures.py

class MergeDict(object):
    """
    A simple class for creating new "virtual" dictionaries that actually look
    up values in more than one dictionary, passed in the constructor.

    If a key appears in more than one of the given dictionaries, only the
    first occurrence will be used.
    """
    def __init__(self, *dicts):
        self.dicts = dicts

    def __getitem__(self, key):
        for dict_ in self.dicts:
            try:
                return dict_[key]
            except KeyError:
                pass
        raise KeyError

    def __copy__(self):
        return self.__class__(*self.dicts)

    def get(self, key, default=None):
        try:
            return self[key]
        except KeyError:
            return default

    def getlist(self, key):
        for dict_ in self.dicts:
            if key in dict_.keys():
                return dict_.getlist(key)
        return []

    def items(self):
        item_list = []
        for dict_ in self.dicts:
            item_list.extend(dict_.items())
        return item_list

    def has_key(self, key):
        for dict_ in self.dicts:
            if key in dict_:
                return True
        return False

    __contains__ = has_key

    def copy(self):
        """Returns a copy of this object."""
        return self.__copy__()

class SortedDict(dict):
    """
    A dictionary that keeps its keys in the order in which they're inserted.
    """
    def __new__(cls, *args, **kwargs):
        instance = super(SortedDict, cls).__new__(cls, *args, **kwargs)
        instance.keyOrder = []
        return instance

    def __init__(self, data=None):
        if data is None:
            data = {}
        super(SortedDict, self).__init__(data)
        if isinstance(data, dict):
            self.keyOrder = data.keys()
        else:
            self.keyOrder = []
            for key, value in data:
                if key not in self.keyOrder:
                    self.keyOrder.append(key)

    def __deepcopy__(self, memo):
        from copy import deepcopy
        return self.__class__([(key, deepcopy(value, memo))
                               for key, value in self.iteritems()])

    def __setitem__(self, key, value):
        super(SortedDict, self).__setitem__(key, value)
        if key not in self.keyOrder:
            self.keyOrder.append(key)

    def __delitem__(self, key):
        super(SortedDict, self).__delitem__(key)
        self.keyOrder.remove(key)

    def __iter__(self):
        for k in self.keyOrder:
            yield k

    def pop(self, k, *args):
        result = super(SortedDict, self).pop(k, *args)
        try:
            self.keyOrder.remove(k)
        except ValueError:
            # Key wasn't in the dictionary in the first place. No problem.
            pass
        return result

    def popitem(self):
        result = super(SortedDict, self).popitem()
        self.keyOrder.remove(result[0])
        return result

    def items(self):
        return zip(self.keyOrder, self.values())

    def iteritems(self):
        for key in self.keyOrder:
            yield key, super(SortedDict, self).__getitem__(key)

    def keys(self):
        return self.keyOrder[:]

    def iterkeys(self):
        return iter(self.keyOrder)

    def values(self):
        return [super(SortedDict, self).__getitem__(k) for k in self.keyOrder]

    def itervalues(self):
        for key in self.keyOrder:
            yield super(SortedDict, self).__getitem__(key)

    def update(self, dict_):
        for k, v in dict_.items():
            self.__setitem__(k, v)

    def setdefault(self, key, default):
        if key not in self.keyOrder:
            self.keyOrder.append(key)
        return super(SortedDict, self).setdefault(key, default)

    def value_for_index(self, index):
        """Returns the value of the item at the given zero-based index."""
        return self[self.keyOrder[index]]

    def insert(self, index, key, value):
        """Inserts the key, value pair before the item with the given index."""
        if key in self.keyOrder:
            n = self.keyOrder.index(key)
            del self.keyOrder[n]
            if n < index:
                index -= 1
        self.keyOrder.insert(index, key)
        super(SortedDict, self).__setitem__(key, value)

    def copy(self):
        """Returns a copy of this object."""
        # This way of initializing the copy means it works for subclasses, too.
        obj = self.__class__(self)
        obj.keyOrder = self.keyOrder[:]
        return obj

    def __repr__(self):
        """
        Replaces the normal dict.__repr__ with a version that returns the keys
        in their sorted order.
        """
        return '{%s}' % ', '.join(['%r: %r' % (k, v) for k, v in self.items()])

    def clear(self):
        super(SortedDict, self).clear()
        self.keyOrder = []

class MultiValueDictKeyError(KeyError):
    pass

class MultiValueDict(dict):
    """
    A subclass of dictionary customized to handle multiple values for the
    same key.

    >>> d = MultiValueDict({'name': ['Adrian', 'Simon'], 'position': ['Developer']})
    >>> d['name']
    'Simon'
    >>> d.getlist('name')
    ['Adrian', 'Simon']
    >>> d.get('lastname', 'nonexistent')
    'nonexistent'
    >>> d.setlist('lastname', ['Holovaty', 'Willison'])

    This class exists to solve the irritating problem raised by cgi.parse_qs,
    which returns a list for every key, even though most Web forms submit
    single name-value pairs.
    """
    def __init__(self, key_to_list_mapping=()):
        super(MultiValueDict, self).__init__(key_to_list_mapping)

    def __repr__(self):
        return "<%s: %s>" % (self.__class__.__name__,
                             super(MultiValueDict, self).__repr__())

    def __getitem__(self, key):
        """
        Returns the last data value for this key, or [] if it's an empty list;
        raises KeyError if not found.
        """
        try:
            list_ = super(MultiValueDict, self).__getitem__(key)
        except KeyError:
            raise MultiValueDictKeyError, "Key %r not found in %r" % (key, self)
        try:
            return list_[-1]
        except IndexError:
            return []

    def __setitem__(self, key, value):
        super(MultiValueDict, self).__setitem__(key, [value])

    def __copy__(self):
        return self.__class__(super(MultiValueDict, self).items())

    def __deepcopy__(self, memo=None):
        import copy
        if memo is None:
            memo = {}
        result = self.__class__()
        memo[id(self)] = result
        for key, value in dict.items(self):
            dict.__setitem__(result, copy.deepcopy(key, memo),
                             copy.deepcopy(value, memo))
        return result

    def get(self, key, default=None):
        """
        Returns the last data value for the passed key. If key doesn't exist
        or value is an empty list, then default is returned.
        """
        try:
            val = self[key]
        except KeyError:
            return default
        if val == []:
            return default
        return val

    def getlist(self, key):
        """
        Returns the list of values for the passed key. If key doesn't exist,
        then an empty list is returned.
        """
        try:
            return super(MultiValueDict, self).__getitem__(key)
        except KeyError:
            return []

    def setlist(self, key, list_):
        super(MultiValueDict, self).__setitem__(key, list_)

    def setdefault(self, key, default=None):
        if key not in self:
            self[key] = default
        return self[key]

    def setlistdefault(self, key, default_list=()):
        if key not in self:
            self.setlist(key, default_list)
        return self.getlist(key)

    def appendlist(self, key, value):
        """Appends an item to the internal list associated with key."""
        self.setlistdefault(key, [])
        super(MultiValueDict, self).__setitem__(key, self.getlist(key) + [value])

    def items(self):
        """
        Returns a list of (key, value) pairs, where value is the last item in
        the list associated with the key.
        """
        return [(key, self[key]) for key in self.keys()]

    def iteritems(self):
        """
        Yields (key, value) pairs, where value is the last item in the list
        associated with the key.
        """
        for key in self.keys():
            yield (key, self[key])

    def lists(self):
        """Returns a list of (key, list) pairs."""
        return super(MultiValueDict, self).items()

    def values(self):
        """Returns a list of the last value on every key list."""
        return [self[key] for key in self.keys()]

    def copy(self):
        """Returns a copy of this object."""
        return self.__deepcopy__()

    def update(self, *args, **kwargs):
        """
        update() extends rather than replaces existing key lists.
        Also accepts keyword args.
        """
        if len(args) > 1:
            raise TypeError, "update expected at most 1 arguments, got %d" % len(args)
        if args:
            other_dict = args[0]
            if isinstance(other_dict, MultiValueDict):
                for key, value_list in other_dict.lists():
                    self.setlistdefault(key, []).extend(value_list)
            else:
                try:
                    for key, value in other_dict.items():
                        self.setlistdefault(key, []).append(value)
                except TypeError:
                    raise ValueError, "MultiValueDict.update() takes either a MultiValueDict or dictionary"
        for key, value in kwargs.iteritems():
            self.setlistdefault(key, []).append(value)

class DotExpandedDict(dict):
    """
    A special dictionary constructor that takes a dictionary in which the keys
    may contain dots to specify inner dictionaries. It's confusing, but this
    example should make sense.

    >>> d = DotExpandedDict({'person.1.firstname': ['Simon'], \
            'person.1.lastname': ['Willison'], \
            'person.2.firstname': ['Adrian'], \
            'person.2.lastname': ['Holovaty']})
    >>> d
    {'person': {'1': {'lastname': ['Willison'], 'firstname': ['Simon']}, '2': {'lastname': ['Holovaty'], 'firstname': ['Adrian']}}}
    >>> d['person']
    {'1': {'lastname': ['Willison'], 'firstname': ['Simon']}, '2': {'lastname': ['Holovaty'], 'firstname': ['Adrian']}}
    >>> d['person']['1']
    {'lastname': ['Willison'], 'firstname': ['Simon']}

    # Gotcha: Results are unpredictable if the dots are "uneven":
    >>> DotExpandedDict({'c.1': 2, 'c.2': 3, 'c': 1})
    {'c': 1}
    """
    def __init__(self, key_to_list_mapping):
        for k, v in key_to_list_mapping.items():
            current = self
            bits = k.split('.')
            for bit in bits[:-1]:
                current = current.setdefault(bit, {})
            # Now assign value to current position
            try:
                current[bits[-1]] = v
            except TypeError: # Special-case if current isn't a dict.
                current = {bits[-1]: v}

class ImmutableList(tuple):
    """
    A tuple-like object that raises useful errors when it is asked to mutate.

    Example::

        >>> a = ImmutableList(range(5), warning="You cannot mutate this.")
        >>> a[3] = '4'
        Traceback (most recent call last):
            ...
        AttributeError: You cannot mutate this.
    """

    def __new__(cls, *args, **kwargs):
        if 'warning' in kwargs:
            warning = kwargs['warning']
            del kwargs['warning']
        else:
            warning = 'ImmutableList object is immutable.'
        self = tuple.__new__(cls, *args, **kwargs)
        self.warning = warning
        return self

    def complain(self, *wargs, **kwargs):
        if isinstance(self.warning, Exception):
            raise self.warning
        else:
            raise AttributeError, self.warning

    # All list mutation functions complain.
    __delitem__  = complain
    __delslice__ = complain
    __iadd__     = complain
    __imul__     = complain
    __setitem__  = complain
    __setslice__ = complain
    append       = complain
    extend       = complain
    insert       = complain
    pop          = complain
    remove       = complain
    sort         = complain
    reverse      = complain

class DictWrapper(dict):
    """
    Wraps accesses to a dictionary so that certain values (those starting with
    the specified prefix) are passed through a function before being returned.
    The prefix is removed before looking up the real value.

    Used by the SQL construction code to ensure that values are correctly
    quoted before being used.
    """
    def __init__(self, data, func, prefix):
        super(DictWrapper, self).__init__(data)
        self.func = func
        self.prefix = prefix

    def __getitem__(self, key):
        """
        Retrieves the real value after stripping the prefix string (if
        present). If the prefix is present, pass the value through self.func
        before returning, otherwise return the raw value.
        """
        if key.startswith(self.prefix):
            use_func = True
            key = key[len(self.prefix):]
        else:
            use_func = False
        value = super(DictWrapper, self).__getitem__(key)
        if use_func:
            return self.func(value)
        return value