zip

  • 把两个可迭代内容生成一个可迭代的tuple元素类型组成的内容 
l1 = [ 1,2,3,4,5]
l2 = [11,22,33,44,55]

z = zip(l1, l2)

print(type(z))
print(z)

for i in z:
    print(i)
<class 'zip'>
<zip object at 0x7f61c457ab88>
(1, 11)
(2, 22)
(3, 33)
(4, 44)
(5, 55)

 

enumerate

  • 跟zip比较像功能
  • 对可迭代对象里的每一元素，配上一个索引，然后索引和内容构成tuple类型 
em = enumerate(l1, start=100)

l2 = [ i for i in em]
print(l2)
[(100, 11), (101, 22), (102, 33), (103, 44), (104, 55)]

 collections模块

     - namedtuple
     - deque

namedtuple

  • tuple类型
  • 是一个可命名的tuple 
import collections
Point1 = collections.namedtuple("Point2", ['x', 'y'])
p = Point1(11, 22) 
print(p.x)
print(p[0])


11
11

 

Circle = collections.namedtuple("Circle", ['x', 'y', 'r'])

c = Circle(100, 150, 50)
print(c)
print(type(c))

# 想检测以下namedtuple到底属于谁的子类
isinstance(c, tuple)
Circle(x=100, y=150, r=50)
<class '__main__.Circle'>
True

 # dequeue

- 比较方便的解决了频繁删除插入带来的效率问题

from collections import deque

q = deque(['a', 'b', 'c'])
print(q)

q.append("d")
print(q)

q.appendleft('x')
print(q)
deque(['a', 'b', 'c'])
deque(['a', 'b', 'c', 'd'])
deque(['x', 'a', 'b', 'c', 'd'])

 

 

defaultdict

  • 当直接读取dict不存在的属性时，直接返回默认值 
from collections import defaultdict
# lambda表达式，直接返回字符串
func = lambda: "刘大拿"
d2 = defaultdict(func)

d2["one"] = 1
d2["two"] = 2

print(d2['one'])
print(d2['four'])
1
刘大拿

 

Counter

  • 统计字符串个数 
from collections import Counter

# 为什么下面结果不把abcdefgabced.....作为键值，而是以其中每一个字母作为键值
# 需要括号里内容为可迭代
c = Counter("abcdefgabcdeabcdabcaba")
print(c)
Counter({'a': 6, 'b': 5, 'c': 4, 'd': 3, 'e': 2, 'f': 1, 'g': 1})