April 2023
Intermediate to advanced
769 pages
25h 16m
Chinese
Content preview from 流畅的Python（第2版）
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.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.
22
｜
第
2
章
2.3.2
列表推导式与
map
和
filter
比较
列表推导式涵盖
map
和
filter
两个函数的功能，写出的代码不像
Python
的
lambda
表达式
那样晦涩难懂。请看示例
2-3
。
示例
2-3
使用列表推导式和
map
/
filter
组合构建同一个列表
>>> symbols = '
$¢£¥€¤
'
>>> beyond_ascii = [ord(s) for s in symbols if ord(s) > 127]
>>> beyond_ascii
[162, 163, 165, 8364, 164]
>>> beyond_ascii = list(filter(lambda c: c > 127, map(ord, symbols)))
>>> beyond_ascii
[162, 163, 165, 8364, 164]
我原以为使用
map
和
filter
速度更快，但是
Alex Martelli
告诉我事实并非如此，至少前
面的示例不是这样。本书代码中的
02-array-seq/listcomp_spe
ed.py
脚本对列表推导式和
filter
/
map
的速度进行了简单比较。
map
和
filter
将在第
7
章深入讨论。下面来看如何使用列表推导式计算笛卡儿积，即构建
一个列表，其中包含两个或更多列表中的所有项组成的元组。
2.3.3
笛卡儿积
列表推导式可以根据两个或更多可迭代对象的笛卡儿积构建列表。笛卡儿积的每一项是一
个元组，由输入的各个可迭代对象中的项构成。得到的列表长度等于输入的各个可迭代对 ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
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.