Python之第二十八天的努力--collections模块

Posted 2020-12-14 szheng

01 collections模块

1. namedtuple() 命名元组

   # namedtuple() 命名元组
   Rectangle = collections.namedtuple(‘Rectangle_class‘,[‘length‘,‘width‘])
   #
   r = Rectangle(10,5)
   # 通过属性访问元组的元素
   print(r.length)         # 10
   print(r.width)          # 5
   

2. defautldict() 默认值字典

   # defautldict()  默认值字典
   # 创建一个字典的方法：
   # 1.直接创建
   # dic = {‘name‘:‘zs‘,‘age‘:18}
   # 2.
   # dic = dict([(‘name‘,‘zs‘),(‘age‘,18)])
   # 3.
   # dic = {k:v for k,v in [(1,2),(3,4)]}
   
   #
   dic = collections.defaultdict(int,name=‘zs‘,age=18)
   print(dic[‘name‘])          # zs
   print(dic[‘age‘])           # 18
   print(dic[‘aaa‘])           # 0 ---> 和int对应，且把{‘aaa‘:0}添加进来。
   print(dic)                  # defaultdict(<class ‘int‘>, {‘name‘: ‘zs‘, ‘age‘: 18, ‘aaa‘: 0})
   
   # 自定义函数充当第一个参数：
   # 要求，不能有参数
   def func():
       return ‘hello‘
   
   dic = collections.defaultdict(func,name=‘zs‘,age=18)
   print(dic[‘aaa‘])               # hello
   print(dic)                      # defaultdict(<function func at 0x02E517C8>, {‘name‘: ‘zs‘, ‘age‘: 18, ‘aaa‘: ‘hello‘})
   

3. Counter:计数器

   # Counter:计数器
   c = collections.Counter(‘abcdcadaadcag‘)
   print(c)                    # Counter({‘a‘: 5, ‘c‘: 3, ‘d‘: 3, ‘b‘: 1, ‘g‘: 1})
   print(c.most_common(3))     # [(‘a‘, 5), (‘c‘, 3), (‘d‘, 3)]
   

02 模块总结

1. 自定义模块
2. random
3. time
4. datetime
5. os
6. sys
7. json
8. pickle
9. hashlib
10. collections