The Collections Module内建collections集合模块

https://www.bilibili.com/video/av17396749/?p=12

Python函数式编程中的迭代器,生成器详解

课程内容

1.iterators are objects that contain other objects
2.some built-in iterators are such as list,dict,tuple, and set.
3.learned the collections module offers other convenient iterators
4.generators are functions that yield and they are also iterators
5.understood that fenerators allow for lazy evaluation and coroutines,or light-weight threading.

以下是笔记

collections.namedtuple

namedtuple() is a factory function;that is,it generates a class,and not an instance of a class(an object)

two steps：
1.First,use namedtuple() to generate a class
2.then create an instance of this class

 from collections import namedtuple
 Person=namedtuple('Person',['name','age'])
 jay_z=Person(name='Sean Carter',age=47)
 print('%s is %s years old'%(jay_z.name,jay_z.age))
 print('%s is %s years old'%(jay_z[0],jay_z[1]))

 输出

 Sean Carter is 47 years old
 Sean Carter is 47 years old

collections.OrderedDict

 from collections import OrderedDict
 d=OrderedDict([
 ('Lizard','Reptile'),
 ('Whale','Mammal')
 ]
 )

 for species,_class in d.items():
 print('%s is a %s'%(species,_class))

 输出：

 Lizard is a Reptile
 Whale is a Mammal

collections.defaultdict

 from collections import defaultdict
 languages={
 'Jack':'java',
 'Pony':'Ruby',
 'Sara':'javascript'
 }
 d=defaultdict(lambda:'Python')
 d.update(languages)

 输出:
 python