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python中的容器类——collections

本文简单梳理了 python 中的容器类 collections 提供的便利工具集（wrapper toolset）。

collections — Container datatypes

  • namedtuple()（命名元组）: factory function for creating tuple subclasses with named fields
  • deque（双端队列）: list-like container with fast appends and pops on either end
  • ChainMap（链接字典）: dict-like class for creating a single view of multiple mappings
  • Counter（计数器）: dict subclass for counting hashable objects
  • OrderedDict（有序字典）: dict subclass that remembers the order entries were added
  • defaultdict: dict subclass that calls a factory function to supply missing values
  • UserDict: wrapper around dictionary objects for easier dict subclassing
  • UserList: wrapper around list objects for easier list subclassing
  • UserString: wrapper around string objects for easier string subclassing

help#

>>> import collections
>>> help(collections)

Help on package collections:

NAME
    collections

DESCRIPTION
    This module implements specialized container datatypes providing
    alternatives to Python's general purpose built-in containers, dict,
    list, set, and tuple.

    * namedtuple   factory function for creating tuple subclasses with named fields
    * deque        list-like container with fast appends and pops on either end
    * ChainMap     dict-like class for creating a single view of multiple mappings
    * Counter      dict subclass for counting hashable objects
    * OrderedDict  dict subclass that remembers the order entries were added
    * defaultdict  dict subclass that calls a factory function to supply missing values
    * UserDict     wrapper around dictionary objects for easier dict subclassing
    * UserList     wrapper around list objects for easier list subclassing
    * UserString   wrapper around string objects for easier string subclassing

OrderedDict#

Converting dict to OrderedDict

import collections

Joe = {"Age": 28, "Race": "Latino", "Job": "Nurse"}
Bob = {"Age": 25, "Race": "White", "Job": "Mechanic", "Random": "stuff"}

#Just for clarity:
Joe = collections.OrderedDict(Joe)
Bob = collections.OrderedDict(Bob)

print(Joe)
# OrderedDict([('Age', 28), ('Race', 'Latino'), ('Job', 'Nurse')])
print(Bob)
# OrderedDict([('Age', 25), ('Race', 'White'), ('Job', 'Mechanic'), ('Random', 'stuff')])

OrderedSet#

Does Python have an ordered set?

orderedset

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