python常用数据结构

0. 字典初始化

d = {‘a’:1,’b’:2}

或 d={}

d[‘a’] = 1

d[‘b’] = 2

是不是和json格式数据很相似，语法和JavaScript又很相似

1. 变量接受序列分解：

p = (3.14,8.23)

X,Y = p

print(x,y)

3.14,8.23

2. Collections.deque 固定长度队列。

>>> from collections import deque

>>> p = deque(maxlen = 2)

>>> p.append(3.14)

>>> p.append(8.23)

>>> p

deque([3.14, 8.23], maxlen=2)

3. heapq 最大值最小值。

>>> import heapq

>>> p = [3.14,8.23,7.10]

>>> heapq.nlargest(1,p)

[8.23]

>>> heapq.nsmallest(1,p)

[3.14]

5．找出两个字典相同键 和相同项

>>> from collections import OrderedDict

>>> d = {}

>>> d['a'] = 1

>>> d['c'] = 3

>>> d['b'] = 2

>>> dd = {}

>>> dd['a'] = 3

>>> dd['e'] = 5

>>> dd['b'] = 2

>>> d.keys() & dd.keys()

{'a', 'b'}

>>> d.items() & dd.items()

{('b', 2)}

6 去除数组或字典值重复的元素 set

>>> d ={1,1,2,2,3,3,4,5}

>>> set(d)

{1, 2, 3, 4, 5}

7 截取数组元素

>>> d = [1,1,2,2,3,3,4,5]

>>> d[2:4]

[2, 2]

>>> d[2:5]

[2, 2, 3]

8 统计元素出现次数Counter.most_common。

>>> d = [1,1,1,2,2,4,5]

>>> from collections import Counter

>>> master = Counter(d).most_common(2)

>>> print(master)

[(1, 3), (2, 2)]

4. collections.OrderedDict 有序字典

>>> from collections import OrderedDict

>>> d = OrderedDict()

>>> d['a'] = 1

>>> d['c'] = 3

>>> d['b'] = 2

>>> print(d)

OrderedDict([('a', 1), ('c', 3), ('b', 2)])

9.数组排序 operator.itemgetter

>>> from operator import itemgetter

>>> d = [2,1,5,4,3]

>>> sorted(d)

[1, 2, 3, 4, 5]

10.字典排序 sort

>>> from operator import itemgetter

>>> p = [{'x':'3','y':'3'},{'x':'4','y':'4'},{'x':'2','y':'2'},{'x':'1','y':'1'}]

>>> p.sort(key=itemgetter('x'))

>>> print(p)

[{'x': '1', 'y': '1'}, {'x': '2', 'y': '2'}, {'x': '3', 'y': '3'}, {'x': '4', 'y': '4'}]

11. lambda 表达式

>>> p = [{'x':'3','y':'3'},{'x':'4','y':'4'},{'x':'2','y':'2'},{'x':'1','y':'1'}]

>>> pLamb = [n['x'] > '2' for n in p]

>>> print(pLamb)

[True, True, False, False]

12 compress 与 11项 结合使用。

>>> from itertools import compress

>>> list(compress(p,pLamb))

[{'x': '3', 'y': '3'}, {'x': '4', 'y': '4'}]

13.逻辑上合并对象

>>> p = {'x':1,'y':2}

>>> p2 = {'y':3,'z':4}

>>> from collections import ChainMap

>>> c = ChainMap(p,p2)

>>> print(c)

ChainMap({'x': 1, 'y': 2}, {'y': 3, 'z': 4})

>>> list(c.keys())

['x', 'z', 'y']