85 lines
2.8 KiB
ReStructuredText
85 lines
2.8 KiB
ReStructuredText
:mod:`collections` -- collection and container types
|
|
====================================================
|
|
|
|
**Limitations:** Not implemented on the smallest CircuitPython boards for space reasons.
|
|
|
|
.. module:: collections
|
|
:synopsis: collection and container types
|
|
|
|
|see_cpython_module| :mod:`python:collections`.
|
|
|
|
This module implements advanced collection and container types to
|
|
hold/accumulate various objects.
|
|
|
|
Classes
|
|
-------
|
|
|
|
.. class:: deque(iterable, maxlen[, flags])
|
|
|
|
Deques (double-ended queues) are a list-like container that support O(1)
|
|
appends and pops from either side of the deque. New deques are created
|
|
using the following arguments:
|
|
|
|
- *iterable* must be the empty tuple, and the new deque is created empty.
|
|
|
|
- *maxlen* must be specified and the deque will be bounded to this
|
|
maximum length. Once the deque is full, any new items added will
|
|
discard items from the opposite end.
|
|
|
|
- The optional *flags* can be 1 to check for overflow when adding items.
|
|
|
|
As well as supporting ``bool`` and ``len``, deque objects have the following
|
|
methods:
|
|
|
|
.. method:: deque.append(x)
|
|
|
|
Add *x* to the right side of the deque.
|
|
Raises IndexError if overflow checking is enabled and there is no more room left.
|
|
|
|
.. method:: deque.popleft()
|
|
|
|
Remove and return an item from the left side of the deque.
|
|
Raises IndexError if no items are present.
|
|
|
|
.. function:: namedtuple(name, fields)
|
|
|
|
This is factory function to create a new namedtuple type with a specific
|
|
name and set of fields. A namedtuple is a subclass of tuple which allows
|
|
to access its fields not just by numeric index, but also with an attribute
|
|
access syntax using symbolic field names. Fields is a sequence of strings
|
|
specifying field names. For compatibility with CPython it can also be a
|
|
a string with space-separated field named (but this is less efficient).
|
|
Example of use::
|
|
|
|
from collections import namedtuple
|
|
|
|
MyTuple = namedtuple("MyTuple", ("id", "name"))
|
|
t1 = MyTuple(1, "foo")
|
|
t2 = MyTuple(2, "bar")
|
|
print(t1.name)
|
|
assert t2.name == t2[1]
|
|
|
|
.. class:: OrderedDict(...)
|
|
|
|
``dict`` type subclass which remembers and preserves the order of keys
|
|
added. When ordered dict is iterated over, keys/items are returned in
|
|
the order they were added::
|
|
|
|
from collections import OrderedDict
|
|
|
|
# To make benefit of ordered keys, OrderedDict should be initialized
|
|
# from sequence of (key, value) pairs.
|
|
d = OrderedDict([("z", 1), ("a", 2)])
|
|
# More items can be added as usual
|
|
d["w"] = 5
|
|
d["b"] = 3
|
|
for k, v in d.items():
|
|
print(k, v)
|
|
|
|
Output::
|
|
|
|
z 1
|
|
a 2
|
|
w 5
|
|
b 3
|