# Copyright (c) 2013, Mahmoud Hashemi
#
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"""Python has a very powerful mapping type at its core: the :class:`dict`
type. While versatile and featureful, the :class:`dict` prioritizes
simplicity and performance. As a result, it does not retain the order
of item insertion [1]_, nor does it store multiple values per key. It
is a fast, unordered 1:1 mapping.
The :class:`OrderedMultiDict` contrasts to the built-in :class:`dict`,
as a relatively maximalist, ordered 1:n subtype of
:class:`dict`. Virtually every feature of :class:`dict` has been
retooled to be intuitive in the face of this added
complexity. Additional methods have been added, such as
:class:`collections.Counter`-like functionality.
A prime advantage of the :class:`OrderedMultiDict` (OMD) is its
non-destructive nature. Data can be added to an :class:`OMD` without being
rearranged or overwritten. The property can allow the developer to
work more freely with the data, as well as make more assumptions about
where input data will end up in the output, all without any extra
work.
One great example of this is the :meth:`OMD.inverted()` method, which
returns a new OMD with the values as keys and the keys as values. All
the data and the respective order is still represented in the inverted
form, all from an operation which would be outright wrong and reckless
with a built-in :class:`dict` or :class:`collections.OrderedDict`.
The OMD has been performance tuned to be suitable for a wide range of
usages, including as a basic unordered MultiDict. Special
thanks to `Mark Williams`_ for all his help.
.. [1] As of 2015, `basic dicts on PyPy are ordered
<http://morepypy.blogspot.com/2015/01/faster-more-memory-efficient-and-more.html>`_,
and as of December 2017, `basic dicts in CPython 3 are now ordered
<https://mail.python.org/pipermail/python-dev/2017-December/151283.html>`_, as
well.
.. _Mark Williams: https://github.com/markrwilliams
"""
from collections.abc import KeysView, ValuesView, ItemsView
from itertools import zip_longest
try:
from .typeutils import make_sentinel
_MISSING = make_sentinel(var_name='_MISSING')
except ImportError:
_MISSING = object()
PREV, NEXT, KEY, VALUE, SPREV, SNEXT = range(6)
__all__ = ['MultiDict', 'OMD', 'OrderedMultiDict', 'OneToOne', 'ManyToMany', 'subdict', 'FrozenDict']
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class OrderedMultiDict(dict):
"""A MultiDict is a dictionary that can have multiple values per key
and the OrderedMultiDict (OMD) is a MultiDict that retains
original insertion order. Common use cases include:
* handling query strings parsed from URLs
* inverting a dictionary to create a reverse index (values to keys)
* stacking data from multiple dictionaries in a non-destructive way
The OrderedMultiDict constructor is identical to the built-in
:class:`dict`, and overall the API constitutes an intuitive
superset of the built-in type:
>>> omd = OrderedMultiDict()
>>> omd['a'] = 1
>>> omd['b'] = 2
>>> omd.add('a', 3)
>>> omd.get('a')
3
>>> omd.getlist('a')
[1, 3]
Some non-:class:`dict`-like behaviors also make an appearance,
such as support for :func:`reversed`:
>>> list(reversed(omd))
['b', 'a']
Note that unlike some other MultiDicts, this OMD gives precedence
to the most recent value added. ``omd['a']`` refers to ``3``, not
``1``.
>>> omd
OrderedMultiDict([('a', 1), ('b', 2), ('a', 3)])
>>> omd.poplast('a')
3
>>> omd
OrderedMultiDict([('a', 1), ('b', 2)])
>>> omd.pop('a')
1
>>> omd
OrderedMultiDict([('b', 2)])
If you want a safe-to-modify or flat dictionary, use
:meth:`OrderedMultiDict.todict()`.
>>> from pprint import pprint as pp # preserve printed ordering
>>> omd = OrderedMultiDict([('a', 1), ('b', 2), ('a', 3)])
>>> pp(omd.todict())
{'a': 3, 'b': 2}
>>> pp(omd.todict(multi=True))
{'a': [1, 3], 'b': [2]}
With ``multi=False``, items appear with the keys in to original
insertion order, alongside the most-recently inserted value for
that key.
>>> OrderedMultiDict([('a', 1), ('b', 2), ('a', 3)]).items(multi=False)
[('a', 3), ('b', 2)]
.. warning::
``dict(omd)`` changed behavior `in Python 3.7
<https://bugs.python.org/issue34320>`_ due to changes made to
support the transition from :class:`collections.OrderedDict` to
the built-in dictionary being ordered. Before 3.7, the result
would be a new dictionary, with values that were lists, similar
to ``omd.todict(multi=True)`` (but only shallow-copy; the lists
were direct references to OMD internal structures). From 3.7
onward, the values became singular, like
``omd.todict(multi=False)``. For reliable cross-version
behavior, just use :meth:`~OrderedMultiDict.todict()`.
"""
def __new__(cls, *a, **kw):
ret = super().__new__(cls)
ret._clear_ll()
return ret
def __init__(self, *args, **kwargs):
if len(args) > 1:
raise TypeError('%s expected at most 1 argument, got %s'
% (self.__class__.__name__, len(args)))
super().__init__()
if args:
self.update_extend(args[0])
if kwargs:
self.update(kwargs)
def __getstate__(self):
return list(self.iteritems(multi=True))
def __setstate__(self, state):
self.clear()
self.update_extend(state)
def _clear_ll(self):
try:
_map = self._map
except AttributeError:
_map = self._map = {}
self.root = []
_map.clear()
self.root[:] = [self.root, self.root, None]
def _insert(self, k, v):
root = self.root
cells = self._map.setdefault(k, [])
last = root[PREV]
cell = [last, root, k, v]
last[NEXT] = root[PREV] = cell
cells.append(cell)
[文档]
def add(self, k, v):
"""Add a single value *v* under a key *k*. Existing values under *k*
are preserved.
"""
values = super().setdefault(k, [])
self._insert(k, v)
values.append(v)
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def addlist(self, k, v):
"""Add an iterable of values underneath a specific key, preserving
any values already under that key.
>>> omd = OrderedMultiDict([('a', -1)])
>>> omd.addlist('a', range(3))
>>> omd
OrderedMultiDict([('a', -1), ('a', 0), ('a', 1), ('a', 2)])
Called ``addlist`` for consistency with :meth:`getlist`, but
tuples and other sequences and iterables work.
"""
if not v:
return
self_insert = self._insert
values = super().setdefault(k, [])
for subv in v:
self_insert(k, subv)
values.extend(v)
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def get(self, k, default=None):
"""Return the value for key *k* if present in the dictionary, else
*default*. If *default* is not given, ``None`` is returned.
This method never raises a :exc:`KeyError`.
To get all values under a key, use :meth:`OrderedMultiDict.getlist`.
"""
return super().get(k, [default])[-1]
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def getlist(self, k, default=_MISSING):
"""Get all values for key *k* as a list, if *k* is in the
dictionary, else *default*. The list returned is a copy and
can be safely mutated. If *default* is not given, an empty
:class:`list` is returned.
"""
try:
return super().__getitem__(k)[:]
except KeyError:
if default is _MISSING:
return []
return default
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def clear(self):
"Empty the dictionary."
super().clear()
self._clear_ll()
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def setdefault(self, k, default=_MISSING):
"""If key *k* is in the dictionary, return its value. If not, insert
*k* with a value of *default* and return *default*. *default*
defaults to ``None``. See :meth:`dict.setdefault` for more
information.
"""
if not super().__contains__(k):
self[k] = None if default is _MISSING else default
return self[k]
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def copy(self):
"Return a shallow copy of the dictionary."
return self.__class__(self.iteritems(multi=True))
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@classmethod
def fromkeys(cls, keys, default=None):
"""Create a dictionary from a list of keys, with all the values
set to *default*, or ``None`` if *default* is not set.
"""
return cls([(k, default) for k in keys])
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def update(self, E, **F):
"""Add items from a dictionary or iterable (and/or keyword arguments),
overwriting values under an existing key. See
:meth:`dict.update` for more details.
"""
# E and F are throwback names to the dict() __doc__
if E is self:
return
self_add = self.add
if isinstance(E, OrderedMultiDict):
for k in E:
if k in self:
del self[k]
for k, v in E.iteritems(multi=True):
self_add(k, v)
elif callable(getattr(E, 'keys', None)):
for k in E.keys():
self[k] = E[k]
else:
seen = set()
seen_add = seen.add
for k, v in E:
if k not in seen and k in self:
del self[k]
seen_add(k)
self_add(k, v)
for k in F:
self[k] = F[k]
return
[文档]
def update_extend(self, E, **F):
"""Add items from a dictionary, iterable, and/or keyword
arguments without overwriting existing items present in the
dictionary. Like :meth:`update`, but adds to existing keys
instead of overwriting them.
"""
if E is self:
iterator = iter(E.items())
elif isinstance(E, OrderedMultiDict):
iterator = E.iteritems(multi=True)
elif hasattr(E, 'keys'):
iterator = ((k, E[k]) for k in E.keys())
else:
iterator = E
self_add = self.add
for k, v in iterator:
self_add(k, v)
def __setitem__(self, k, v):
if super().__contains__(k):
self._remove_all(k)
self._insert(k, v)
super().__setitem__(k, [v])
def __getitem__(self, k):
return super().__getitem__(k)[-1]
def __delitem__(self, k):
super().__delitem__(k)
self._remove_all(k)
def __eq__(self, other):
if self is other:
return True
try:
if len(other) != len(self):
return False
except TypeError:
return False
if isinstance(other, OrderedMultiDict):
selfi = self.iteritems(multi=True)
otheri = other.iteritems(multi=True)
zipped_items = zip_longest(selfi, otheri, fillvalue=(None, None))
for (selfk, selfv), (otherk, otherv) in zipped_items:
if selfk != otherk or selfv != otherv:
return False
if not(next(selfi, _MISSING) is _MISSING
and next(otheri, _MISSING) is _MISSING):
# leftovers (TODO: watch for StopIteration?)
return False
return True
elif hasattr(other, 'keys'):
for selfk in self:
try:
other[selfk] == self[selfk]
except KeyError:
return False
return True
return False
def __ne__(self, other):
return not (self == other)
def __ior__(self, other):
self.update(other)
return self
[文档]
def pop(self, k, default=_MISSING):
"""Remove all values under key *k*, returning the most-recently
inserted value. Raises :exc:`KeyError` if the key is not
present and no *default* is provided.
"""
try:
return self.popall(k)[-1]
except KeyError:
if default is _MISSING:
raise KeyError(k)
return default
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def popall(self, k, default=_MISSING):
"""Remove all values under key *k*, returning them in the form of
a list. Raises :exc:`KeyError` if the key is not present and no
*default* is provided.
"""
super_self = super()
if super_self.__contains__(k):
self._remove_all(k)
if default is _MISSING:
return super_self.pop(k)
return super_self.pop(k, default)
[文档]
def poplast(self, k=_MISSING, default=_MISSING):
"""Remove and return the most-recently inserted value under the key
*k*, or the most-recently inserted key if *k* is not
provided. If no values remain under *k*, it will be removed
from the OMD. Raises :exc:`KeyError` if *k* is not present in
the dictionary, or the dictionary is empty.
"""
if k is _MISSING:
if self:
k = self.root[PREV][KEY]
else:
if default is _MISSING:
raise KeyError('empty %r' % type(self))
return default
try:
self._remove(k)
except KeyError:
if default is _MISSING:
raise KeyError(k)
return default
values = super().__getitem__(k)
v = values.pop()
if not values:
super().__delitem__(k)
return v
def _remove(self, k):
values = self._map[k]
cell = values.pop()
cell[PREV][NEXT], cell[NEXT][PREV] = cell[NEXT], cell[PREV]
if not values:
del self._map[k]
def _remove_all(self, k):
values = self._map[k]
while values:
cell = values.pop()
cell[PREV][NEXT], cell[NEXT][PREV] = cell[NEXT], cell[PREV]
del self._map[k]
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def iteritems(self, multi=False):
"""Iterate over the OMD's items in insertion order. By default,
yields only the most-recently inserted value for each key. Set
*multi* to ``True`` to get all inserted items.
"""
root = self.root
curr = root[NEXT]
if multi:
while curr is not root:
yield curr[KEY], curr[VALUE]
curr = curr[NEXT]
else:
for key in self.iterkeys():
yield key, self[key]
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def iterkeys(self, multi=False):
"""Iterate over the OMD's keys in insertion order. By default, yields
each key once, according to the most recent insertion. Set
*multi* to ``True`` to get all keys, including duplicates, in
insertion order.
"""
root = self.root
curr = root[NEXT]
if multi:
while curr is not root:
yield curr[KEY]
curr = curr[NEXT]
else:
yielded = set()
yielded_add = yielded.add
while curr is not root:
k = curr[KEY]
if k not in yielded:
yielded_add(k)
yield k
curr = curr[NEXT]
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def itervalues(self, multi=False):
"""Iterate over the OMD's values in insertion order. By default,
yields the most-recently inserted value per unique key. Set
*multi* to ``True`` to get all values according to insertion
order.
"""
for k, v in self.iteritems(multi=multi):
yield v
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def todict(self, multi=False):
"""Gets a basic :class:`dict` of the items in this dictionary. Keys
are the same as the OMD, values are the most recently inserted
values for each key.
Setting the *multi* arg to ``True`` is yields the same
result as calling :class:`dict` on the OMD, except that all the
value lists are copies that can be safely mutated.
"""
if multi:
return {k: self.getlist(k) for k in self}
return {k: self[k] for k in self}
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def sorted(self, key=None, reverse=False):
"""Similar to the built-in :func:`sorted`, except this method returns
a new :class:`OrderedMultiDict` sorted by the provided key
function, optionally reversed.
Args:
key (callable): A callable to determine the sort key of
each element. The callable should expect an **item**
(key-value pair tuple).
reverse (bool): Set to ``True`` to reverse the ordering.
>>> omd = OrderedMultiDict(zip(range(3), range(3)))
>>> omd.sorted(reverse=True)
OrderedMultiDict([(2, 2), (1, 1), (0, 0)])
Note that the key function receives an **item** (key-value
tuple), so the recommended signature looks like:
>>> omd = OrderedMultiDict(zip('hello', 'world'))
>>> omd.sorted(key=lambda i: i[1]) # i[0] is the key, i[1] is the val
OrderedMultiDict([('o', 'd'), ('l', 'l'), ('e', 'o'), ('l', 'r'), ('h', 'w')])
"""
cls = self.__class__
return cls(sorted(self.iteritems(multi=True), key=key, reverse=reverse))
[文档]
def sortedvalues(self, key=None, reverse=False):
"""Returns a copy of the :class:`OrderedMultiDict` with the same keys
in the same order as the original OMD, but the values within
each keyspace have been sorted according to *key* and
*reverse*.
Args:
key (callable): A single-argument callable to determine
the sort key of each element. The callable should expect
an **item** (key-value pair tuple).
reverse (bool): Set to ``True`` to reverse the ordering.
>>> omd = OrderedMultiDict()
>>> omd.addlist('even', [6, 2])
>>> omd.addlist('odd', [1, 5])
>>> omd.add('even', 4)
>>> omd.add('odd', 3)
>>> somd = omd.sortedvalues()
>>> somd.getlist('even')
[2, 4, 6]
>>> somd.keys(multi=True) == omd.keys(multi=True)
True
>>> omd == somd
False
>>> somd
OrderedMultiDict([('even', 2), ('even', 4), ('odd', 1), ('odd', 3), ('even', 6), ('odd', 5)])
As demonstrated above, contents and key order are
retained. Only value order changes.
"""
try:
superself_iteritems = super().iteritems()
except AttributeError:
superself_iteritems = super().items()
# (not reverse) because they pop off in reverse order for reinsertion
sorted_val_map = {k: sorted(v, key=key, reverse=(not reverse))
for k, v in superself_iteritems}
ret = self.__class__()
for k in self.iterkeys(multi=True):
ret.add(k, sorted_val_map[k].pop())
return ret
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def inverted(self):
"""Returns a new :class:`OrderedMultiDict` with values and keys
swapped, like creating dictionary transposition or reverse
index. Insertion order is retained and all keys and values
are represented in the output.
>>> omd = OMD([(0, 2), (1, 2)])
>>> omd.inverted().getlist(2)
[0, 1]
Inverting twice yields a copy of the original:
>>> omd.inverted().inverted()
OrderedMultiDict([(0, 2), (1, 2)])
"""
return self.__class__((v, k) for k, v in self.iteritems(multi=True))
[文档]
def counts(self):
"""Returns a mapping from key to number of values inserted under that
key. Like :py:class:`collections.Counter`, but returns a new
:class:`OrderedMultiDict`.
"""
# Returns an OMD because Counter/OrderedDict may not be
# available, and neither Counter nor dict maintain order.
super_getitem = super().__getitem__
return self.__class__((k, len(super_getitem(k))) for k in self)
[文档]
def keys(self, multi=False):
"""Returns a list containing the output of :meth:`iterkeys`. See
that method's docs for more details.
"""
return list(self.iterkeys(multi=multi))
[文档]
def values(self, multi=False):
"""Returns a list containing the output of :meth:`itervalues`. See
that method's docs for more details.
"""
return list(self.itervalues(multi=multi))
[文档]
def items(self, multi=False):
"""Returns a list containing the output of :meth:`iteritems`. See
that method's docs for more details.
"""
return list(self.iteritems(multi=multi))
def __iter__(self):
return self.iterkeys()
def __reversed__(self):
root = self.root
curr = root[PREV]
lengths = {}
lengths_sd = lengths.setdefault
get_values = super().__getitem__
while curr is not root:
k = curr[KEY]
vals = get_values(k)
if lengths_sd(k, 1) == len(vals):
yield k
lengths[k] += 1
curr = curr[PREV]
def __repr__(self):
cn = self.__class__.__name__
kvs = ', '.join([repr((k, v)) for k, v in self.iteritems(multi=True)])
return f'{cn}([{kvs}])'
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def viewkeys(self):
"OMD.viewkeys() -> a set-like object providing a view on OMD's keys"
return KeysView(self)
[文档]
def viewvalues(self):
"OMD.viewvalues() -> an object providing a view on OMD's values"
return ValuesView(self)
[文档]
def viewitems(self):
"OMD.viewitems() -> a set-like object providing a view on OMD's items"
return ItemsView(self)
# A couple of convenient aliases
OMD = OrderedMultiDict
MultiDict = OrderedMultiDict
class FastIterOrderedMultiDict(OrderedMultiDict):
"""An OrderedMultiDict backed by a skip list. Iteration over keys
is faster and uses constant memory but adding duplicate key-value
pairs is slower. Brainchild of Mark Williams.
"""
def _clear_ll(self):
# TODO: always reset objects? (i.e., no else block below)
try:
_map = self._map
except AttributeError:
_map = self._map = {}
self.root = []
_map.clear()
self.root[:] = [self.root, self.root,
None, None,
self.root, self.root]
def _insert(self, k, v):
root = self.root
empty = []
cells = self._map.setdefault(k, empty)
last = root[PREV]
if cells is empty:
cell = [last, root,
k, v,
last, root]
# was the last one skipped?
if last[SPREV][SNEXT] is root:
last[SPREV][SNEXT] = cell
last[NEXT] = last[SNEXT] = root[PREV] = root[SPREV] = cell
cells.append(cell)
else:
# if the previous was skipped, go back to the cell that
# skipped it
sprev = last[SPREV] if (last[SPREV][SNEXT] is not last) else last
cell = [last, root,
k, v,
sprev, root]
# skip me
last[SNEXT] = root
last[NEXT] = root[PREV] = root[SPREV] = cell
cells.append(cell)
def _remove(self, k):
cells = self._map[k]
cell = cells.pop()
if not cells:
del self._map[k]
cell[PREV][SNEXT] = cell[SNEXT]
if cell[PREV][SPREV][SNEXT] is cell:
cell[PREV][SPREV][SNEXT] = cell[NEXT]
elif cell[SNEXT] is cell[NEXT]:
cell[SPREV][SNEXT], cell[SNEXT][SPREV] = cell[SNEXT], cell[SPREV]
cell[PREV][NEXT], cell[NEXT][PREV] = cell[NEXT], cell[PREV]
def _remove_all(self, k):
cells = self._map.pop(k)
while cells:
cell = cells.pop()
if cell[PREV][SPREV][SNEXT] is cell:
cell[PREV][SPREV][SNEXT] = cell[NEXT]
elif cell[SNEXT] is cell[NEXT]:
cell[SPREV][SNEXT], cell[SNEXT][SPREV] = cell[SNEXT], cell[SPREV]
cell[PREV][NEXT], cell[NEXT][PREV] = cell[NEXT], cell[PREV]
cell[PREV][SNEXT] = cell[SNEXT]
def iteritems(self, multi=False):
next_link = NEXT if multi else SNEXT
root = self.root
curr = root[next_link]
while curr is not root:
yield curr[KEY], curr[VALUE]
curr = curr[next_link]
def iterkeys(self, multi=False):
next_link = NEXT if multi else SNEXT
root = self.root
curr = root[next_link]
while curr is not root:
yield curr[KEY]
curr = curr[next_link]
def __reversed__(self):
root = self.root
curr = root[PREV]
while curr is not root:
if curr[SPREV][SNEXT] is not curr:
curr = curr[SPREV]
if curr is root:
break
yield curr[KEY]
curr = curr[PREV]
_OTO_INV_MARKER = object()
_OTO_UNIQUE_MARKER = object()
[文档]
class OneToOne(dict):
"""Implements a one-to-one mapping dictionary. In addition to
inheriting from and behaving exactly like the builtin
:class:`dict`, all values are automatically added as keys on a
reverse mapping, available as the `inv` attribute. This
arrangement keeps key and value namespaces distinct.
Basic operations are intuitive:
>>> oto = OneToOne({'a': 1, 'b': 2})
>>> print(oto['a'])
1
>>> print(oto.inv[1])
a
>>> len(oto)
2
Overwrites happens in both directions:
>>> oto.inv[1] = 'c'
>>> print(oto.get('a'))
None
>>> len(oto)
2
For a very similar project, with even more one-to-one
functionality, check out `bidict <https://github.com/jab/bidict>`_.
"""
__slots__ = ('inv',)
def __init__(self, *a, **kw):
raise_on_dupe = False
if a:
if a[0] is _OTO_INV_MARKER:
self.inv = a[1]
dict.__init__(self, [(v, k) for k, v in self.inv.items()])
return
elif a[0] is _OTO_UNIQUE_MARKER:
a, raise_on_dupe = a[1:], True
dict.__init__(self, *a, **kw)
self.inv = self.__class__(_OTO_INV_MARKER, self)
if len(self) == len(self.inv):
# if lengths match, that means everything's unique
return
if not raise_on_dupe:
dict.clear(self)
dict.update(self, [(v, k) for k, v in self.inv.items()])
return
# generate an error message if the values aren't 1:1
val_multidict = {}
for k, v in self.items():
val_multidict.setdefault(v, []).append(k)
dupes = {v: k_list for v, k_list in
val_multidict.items() if len(k_list) > 1}
raise ValueError('expected unique values, got multiple keys for'
' the following values: %r' % dupes)
[文档]
@classmethod
def unique(cls, *a, **kw):
"""This alternate constructor for OneToOne will raise an exception
when input values overlap. For instance:
>>> OneToOne.unique({'a': 1, 'b': 1})
Traceback (most recent call last):
...
ValueError: expected unique values, got multiple keys for the following values: ...
This even works across inputs:
>>> a_dict = {'a': 2}
>>> OneToOne.unique(a_dict, b=2)
Traceback (most recent call last):
...
ValueError: expected unique values, got multiple keys for the following values: ...
"""
return cls(_OTO_UNIQUE_MARKER, *a, **kw)
def __setitem__(self, key, val):
hash(val) # ensure val is a valid key
if key in self:
dict.__delitem__(self.inv, self[key])
if val in self.inv:
del self.inv[val]
dict.__setitem__(self, key, val)
dict.__setitem__(self.inv, val, key)
def __delitem__(self, key):
dict.__delitem__(self.inv, self[key])
dict.__delitem__(self, key)
[文档]
def clear(self):
dict.clear(self)
dict.clear(self.inv)
[文档]
def copy(self):
return self.__class__(self)
[文档]
def pop(self, key, default=_MISSING):
if key in self:
dict.__delitem__(self.inv, self[key])
return dict.pop(self, key)
if default is not _MISSING:
return default
raise KeyError()
[文档]
def popitem(self):
key, val = dict.popitem(self)
dict.__delitem__(self.inv, val)
return key, val
[文档]
def setdefault(self, key, default=None):
if key not in self:
self[key] = default
return self[key]
[文档]
def update(self, dict_or_iterable, **kw):
keys_vals = []
if isinstance(dict_or_iterable, dict):
for val in dict_or_iterable.values():
hash(val)
keys_vals = list(dict_or_iterable.items())
else:
for key, val in dict_or_iterable:
hash(key)
hash(val)
keys_vals = list(dict_or_iterable)
for val in kw.values():
hash(val)
keys_vals.extend(kw.items())
for key, val in keys_vals:
self[key] = val
def __repr__(self):
cn = self.__class__.__name__
dict_repr = dict.__repr__(self)
return f"{cn}({dict_repr})"
# marker for the secret handshake used internally to set up the invert ManyToMany
_PAIRING = object()
[文档]
class ManyToMany:
"""
a dict-like entity that represents a many-to-many relationship
between two groups of objects
behaves like a dict-of-tuples; also has .inv which is kept
up to date which is a dict-of-tuples in the other direction
also, can be used as a directed graph among hashable python objects
"""
def __init__(self, items=None):
self.data = {}
if type(items) is tuple and items and items[0] is _PAIRING:
self.inv = items[1]
else:
self.inv = self.__class__((_PAIRING, self))
if items:
self.update(items)
return
[文档]
def get(self, key, default=frozenset()):
try:
return self[key]
except KeyError:
return default
def __getitem__(self, key):
return frozenset(self.data[key])
def __setitem__(self, key, vals):
vals = set(vals)
if key in self:
to_remove = self.data[key] - vals
vals -= self.data[key]
for val in to_remove:
self.remove(key, val)
for val in vals:
self.add(key, val)
def __delitem__(self, key):
for val in self.data.pop(key):
self.inv.data[val].remove(key)
if not self.inv.data[val]:
del self.inv.data[val]
[文档]
def update(self, iterable):
"""given an iterable of (key, val), add them all"""
if type(iterable) is type(self):
other = iterable
for k in other.data:
if k not in self.data:
self.data[k] = other.data[k]
else:
self.data[k].update(other.data[k])
for k in other.inv.data:
if k not in self.inv.data:
self.inv.data[k] = other.inv.data[k]
else:
self.inv.data[k].update(other.inv.data[k])
elif callable(getattr(iterable, 'keys', None)):
for k in iterable.keys():
self.add(k, iterable[k])
else:
for key, val in iterable:
self.add(key, val)
return
[文档]
def add(self, key, val):
if key not in self.data:
self.data[key] = set()
self.data[key].add(val)
if val not in self.inv.data:
self.inv.data[val] = set()
self.inv.data[val].add(key)
[文档]
def remove(self, key, val):
self.data[key].remove(val)
if not self.data[key]:
del self.data[key]
self.inv.data[val].remove(key)
if not self.inv.data[val]:
del self.inv.data[val]
[文档]
def replace(self, key, newkey):
"""
replace instances of key by newkey
"""
if key not in self.data:
return
self.data[newkey] = fwdset = self.data.pop(key)
for val in fwdset:
revset = self.inv.data[val]
revset.remove(key)
revset.add(newkey)
[文档]
def iteritems(self):
for key in self.data:
for val in self.data[key]:
yield key, val
[文档]
def keys(self):
return self.data.keys()
def __contains__(self, key):
return key in self.data
def __iter__(self):
return self.data.__iter__()
def __len__(self):
return self.data.__len__()
def __eq__(self, other):
return type(self) == type(other) and self.data == other.data
def __repr__(self):
cn = self.__class__.__name__
return f'{cn}({list(self.iteritems())!r})'
[文档]
def subdict(d, keep=None, drop=None):
"""Compute the "subdictionary" of a dict, *d*.
A subdict is to a dict what a subset is a to set. If *A* is a
subdict of *B*, that means that all keys of *A* are present in
*B*.
Returns a new dict with any keys in *drop* removed, and any keys
in *keep* still present, provided they were in the original
dict. *keep* defaults to all keys, *drop* defaults to empty, so
without one of these arguments, calling this function is
equivalent to calling ``dict()``.
>>> from pprint import pprint as pp
>>> pp(subdict({'a': 1, 'b': 2}))
{'a': 1, 'b': 2}
>>> subdict({'a': 1, 'b': 2, 'c': 3}, drop=['b', 'c'])
{'a': 1}
>>> pp(subdict({'a': 1, 'b': 2, 'c': 3}, keep=['a', 'c']))
{'a': 1, 'c': 3}
"""
if keep is None:
keep = d.keys()
if drop is None:
drop = []
keys = set(keep) - set(drop)
return type(d)([(k, v) for k, v in d.items() if k in keys])
class FrozenHashError(TypeError):
pass
[文档]
class FrozenDict(dict):
"""An immutable dict subtype that is hashable and can itself be used
as a :class:`dict` key or :class:`set` entry. What
:class:`frozenset` is to :class:`set`, FrozenDict is to
:class:`dict`.
There was once an attempt to introduce such a type to the standard
library, but it was rejected: `PEP 416 <https://www.python.org/dev/peps/pep-0416/>`_.
Because FrozenDict is a :class:`dict` subtype, it automatically
works everywhere a dict would, including JSON serialization.
"""
__slots__ = ('_hash',)
[文档]
def updated(self, *a, **kw):
"""Make a copy and add items from a dictionary or iterable (and/or
keyword arguments), overwriting values under an existing
key. See :meth:`dict.update` for more details.
"""
data = dict(self)
data.update(*a, **kw)
return type(self)(data)
[文档]
@classmethod
def fromkeys(cls, keys, value=None):
# one of the lesser known and used/useful dict methods
return cls(dict.fromkeys(keys, value))
def __repr__(self):
cn = self.__class__.__name__
return f'{cn}({dict.__repr__(self)})'
def __reduce_ex__(self, protocol):
return type(self), (dict(self),)
def __hash__(self):
try:
ret = self._hash
except AttributeError:
try:
ret = self._hash = hash(frozenset(self.items()))
except Exception as e:
ret = self._hash = FrozenHashError(e)
if ret.__class__ is FrozenHashError:
raise ret
return ret
def __copy__(self):
return self # immutable types don't copy, see tuple's behavior
# block everything else
def _raise_frozen_typeerror(self, *a, **kw):
"raises a TypeError, because FrozenDicts are immutable"
raise TypeError('%s object is immutable' % self.__class__.__name__)
__ior__ = __setitem__ = __delitem__ = update = _raise_frozen_typeerror
setdefault = pop = popitem = clear = _raise_frozen_typeerror
del _raise_frozen_typeerror
# end dictutils.py