_collections

High performance data structures.
- deque:        ordered collection accessible from endpoints only
- defaultdict:  dict subclass with a default value factory

Classes

OrderedDict

Dictionary that remembers insertion order

clear(...)

  od.clear() -> None.  Remove all items from od.

copy(...)

  od.copy() -> a shallow copy of od

fromkeys(iterable, value=None)

  Create a new ordered dictionary with keys from iterable and values set to value.

get(self, key, default=None, /)

  Return the value for key if key is in the dictionary, else default.

items(...)

keys(...)

move_to_end(self, /, key, last=True)

  Move an existing element to the end (or beginning if last is false).

  Raise KeyError if the element does not exist.

pop(...)

  od.pop(k[,d]) -> v, remove specified key and return the corresponding
          value.  If key is not found, d is returned if given, otherwise KeyError
          is raised.

popitem(self, /, last=True)

  Remove and return a (key, value) pair from the dictionary.

  Pairs are returned in LIFO order if last is true or FIFO order if false.

setdefault(self, /, key, default=None)

  Insert key with a value of default if key is not in the dictionary.

  Return the value for key if key is in the dictionary, else default.

update(...)

values(...)

defaultdict

defaultdict(default_factory=None, /, [...]) --> dict with default factory

The default factory is called without arguments to produce
a new value when a key is not present, in __getitem__ only.
A defaultdict compares equal to a dict with the same items.
All remaining arguments are treated the same as if they were
passed to the dict constructor, including keyword arguments.

clear(...)

  D.clear() -> None.  Remove all items from D.

copy(...)

  D.copy() -> a shallow copy of D.

fromkeys(iterable, value=None, /)

  Create a new dictionary with keys from iterable and values set to value.

get(self, key, default=None, /)

  Return the value for key if key is in the dictionary, else default.

items(...)

  D.items() -> a set-like object providing a view on D's items

keys(...)

  D.keys() -> a set-like object providing a view on D's keys

pop(...)

  D.pop(k[,d]) -> v, remove specified key and return the corresponding value.

  If key is not found, default is returned if given, otherwise KeyError is raised

popitem(self, /)

  Remove and return a (key, value) pair as a 2-tuple.

  Pairs are returned in LIFO (last-in, first-out) order.
  Raises KeyError if the dict is empty.

setdefault(self, key, default=None, /)

  Insert key with a value of default if key is not in the dictionary.

  Return the value for key if key is in the dictionary, else default.

update(...)

  D.update([E, ]**F) -> None.  Update D from dict/iterable E and F.
  If E is present and has a .keys() method, then does:  for k in E: D[k] = E[k]
  If E is present and lacks a .keys() method, then does:  for k, v in E: D[k] = v
  In either case, this is followed by: for k in F:  D[k] = F[k]

values(...)

  D.values() -> an object providing a view on D's values

default_factory = <member 'default_factory' of 'collections.defaultdict' objects>
  Factory for default value called by __missing__().

deque

deque([iterable[, maxlen]]) --> deque object

A list-like sequence optimized for data accesses near its endpoints.

append(...)

  Add an element to the right side of the deque.

appendleft(...)

  Add an element to the left side of the deque.

clear(...)

  Remove all elements from the deque.

copy(...)

  Return a shallow copy of a deque.

count(...)

  D.count(value) -> integer -- return number of occurrences of value

extend(...)

  Extend the right side of the deque with elements from the iterable

extendleft(...)

  Extend the left side of the deque with elements from the iterable

index(...)

  D.index(value, [start, [stop]]) -> integer -- return first index of value.
  Raises ValueError if the value is not present.

insert(...)

  D.insert(index, object) -- insert object before index

pop(...)

  Remove and return the rightmost element.

popleft(...)

  Remove and return the leftmost element.

remove(...)

  D.remove(value) -- remove first occurrence of value.

reverse(...)

  D.reverse() -- reverse *IN PLACE*

rotate(...)

  Rotate the deque n steps to the right (default n=1).  If n is negative, rotates left.

maxlen = <attribute 'maxlen' of 'collections.deque' objects>
  maximum size of a deque or None if unbounded