python效率提升模塊（一）

一　heapq模塊

該模塊提供了堆排序算法的實現

1 創建堆和排序

(1) heapq.heappush()
(2) heap.heapify(list)

2 排序

(1) [heapq.heappop(heap) for _ in range(len(nums))]
(2) num1 = sorted(num1); num2 = sorted(num2)
res = heapq.merge(num1, num2)

3 返回最小值

heapq.heappop(nums)

4 刪除堆中最小元素並加入一個元素

heapq.heaprepalce()

5 獲取堆最大或最小值

(1) heapq.nlargest(3, nums)
(2) heapq.nsmallest(3, nums)

這兩個函數還接受一個key參數，用於dict或其他數據結構類型使用
(3) cheap = heapq.nsmallest(3, portfolio, key=lambda s: s[‘price’])
(4) expensive = heapq.nlargest(3, portfolio, key=lambda s: s[‘price’])

二　itertools模塊

"""
迭代工具模塊
"""
import itertools

# 產生ABCD的全排列
itertools.permutations('ABCD')
# 產生ABCDE的五選三組合
itertools.combinations('ABCDE', 3)
# 產生ABCD和123的笛卡爾積
itertools.product('ABCD', '123')
# 產生ABC的無限循環序列
itertools.cycle(('A', 'B', 'C'))

e:

temp3 = itertools.product('ABCD', '123')
for i in temp3:
    print(i)
>>>
('A', '1')
('A', '2')
('A', '3')
('B', '1')
('B', '2')
('B', '3')
('C', '1')
('C', '2')
('C', '3')
('D', '1')
('D', '2')
('D', '3')

三　collections模塊

from collections import Counter

words = [
    'look', 'into', 'my', 'eyes', 'look', 'into', 'my', 'eyes',
    'the', 'eyes', 'the', 'eyes', 'the', 'eyes', 'not', 'around',
    'the', 'eyes', "don't", 'look', 'around', 'the', 'eyes',
    'look', 'into', 'my', 'eyes', "you're", 'under'
]
counter = Counter(words)
print(counter.most_common(3))
>>>
[('eyes', 8), ('the', 5), ('look', 4)]