April 2023
Intermediate to advanced
769 pages
25h 16m
Chinese
Content preview from 流畅的Python（第2版）
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582
｜
第
20
章
➏
倒序排列要检查的数。这里将显示
proc_pool.py
与
procs.py
在行为上的差别。详见本例
后面的说明。
➐
使用
executor
作为上下文管理器。
➑
executor.map
调用返回
check
返回的
PrimeResult
实例，顺序与
numbers
参数相同。
运行示例
20-6
，会发现结果的出现顺序完全是倒序的
，如示例
20-7
所示。相比之下，
procs.py
的输出
（见
19.6.1
节）则取决于各个数的素数检测难度。例如，
procs.py
在靠近顶
部的位置显示
7 777 777 777 777 777
的结果
，因为它有一个较小的因子
7
，所以
is_prime
很快就能判断它不是素数。
相比之下，
7 777 777 536 340 681
是
88 191 709
2
，
is_prime
要用很长时间才能判断它是合
数。判断
7 777 777 777 777 753
是素数的时间更长—
—因此，在
procs.py
的输出中，这两
个数出现在靠近末端的位置。
运行
proc_pool.py
，你不仅会注意到结果倒序显示，还会发现显示
9 999 999 999 999 999
的
结果之后，程序卡住了。
示例
20-7
proc_pool.py
的输出
$ ./proc_pool.py
Checking 20 numbers with 12 processes:
9999999999999999 0.000024s
➊
9999999999999917 P 9.500677s
➋
7777777777777777 ...
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.