标准库中的生成器函数——用于映射的生成器函数

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 1 #演示itertools.accumulate生成器函数
 2 
 3 import itertools
 4 import operator
 5 
 6 
 7 sample = [5, 4, 2, 8, 7, 6, 3, 0, 9, 1]
 8 
 9 e1 = list(itertools.accumulate(sample))
10 print("默认求累计和：", e1)  #[5, 9, 11, 19, 26, 32, 35, 35, 44, 45]
11 
12 e2= list(itertools.accumulate(sample, min))
13 print("传递min函数，求累计结果：", e2)  #[5, 4, 2, 2, 2, 2, 2, 0, 0, 0]
14 
15 e3 = list(itertools.accumulate(sample, max))
16 print("传递max函数，求累计结果：", e3)  #[5, 5, 5, 8, 8, 8, 8, 8, 9, 9]
17 
18 
19 e4 = list(itertools.accumulate(sample, operator.mul))
20 print("传递operator.mul函数，求累计结果：", e4)  #[5, 20, 40, 320, 2240, 13440, 40320, 0, 0, 0]
21 
22 e5 = list(itertools.accumulate(range(1,11), operator.mul))
23 print("累计结果：", e5)  # [1, 2, 6, 24, 120, 720, 5040, 40320, 362880, 3628800]

1

import itertools
import operator



a = list(enumerate('albatroz', start = 1))
print(a)  #[(1, 'a'), (2, 'l'), (3, 'b'), (4, 'a'), (5, 't'), (6, 'r'), (7, 'o'), (8, 'z')]

a1 =list(enumerate('albatroz', start =4))
print(a1)  #[(4, 'a'), (5, 'l'), (6, 'b'), (7, 'a'), (8, 't'), (9, 'r'), (10, 'o'), (11, 'z')]


a3 = list(map(operator.mul, range(11), range(11)))
print(a3)  #[0, 1, 4, 9, 16, 25, 36, 49, 64, 81, 100]


a4 = list(map(operator.mul, range(11), [2, 4, 8]))
print(a4)  #[0, 4, 16]


a5 = list(map(lambda a, b: (a, b), range(11), [2, 4, 8]))  #生成元组对
print(a5)  #[(0, 2), (1, 4), (2, 8)]




a6 = list(itertools.starmap(operator.mul, enumerate('albatroz', 1))) 
print(a6)  #['a', 'll', 'bbb', 'aaaa', 'ttttt', 'rrrrrr', 'ooooooo', 'zzzzzzzz']


sample = [5, 4, 2, 8, 7, 6, 3, 0, 9, 1]

a7 = list(itertools.starmap(lambda a, b: b/a,
 enumerate(itertools.accumulate(sample), 1)))


print(list(itertools.accumulate(sample)))  #[5, 9, 11, 19, 26, 32, 35, 35, 44, 45]
print( list(enumerate(itertools.accumulate(sample), 1)))  
#[(1, 5), (2, 9), (3, 11), (4, 19), (5, 26), (6, 32), (7, 35), (8, 35), (9, 44), (10, 45)]

print(a7)  #[5.0, 4.5, 3.6666666666666665, 4.75, 5.2, 5.333333333333333, 5.0, 4.375, 4.888888888888889, 4.5]

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