July 2017
Intermediate to advanced
398 pages
11h 54m
Chinese
Content preview from Python数据处理
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.
Python
陷阱
｜
365
何时以何种方式调用这些方法。让我们看一下：
def
add_one(default_list=[]):
default_list.append(1)
return
default_list
现在，让我们通过
IPython
研究：
In [2]: add_one()
Out [2]: [1]
In [3]: add_one()
Out [3]: [1, 1]
你可能希望每一个函数调用会返回一个新的列表，只包含一个元素，
1
。相反，两个调用
修改相同的列表对象。而实际上，默认参数在脚本第一次解释的时候被声明。如果每次你
都想要一个新的列表，可以像下面一样重写函数。
def
add_one(default_list=None):
if
default_list
is
None:
default_list = []
default_list.append(1)
return
default_list
现在我们的代码表现得同我们期望的一样：
In [6]: add_one()
Out [6]: [1]
In [7]: add_one()
Out [7]: [1]
In [8]: add_one(default_list=[3])
Out [8]: [3, 1]
现在你对内存管理和默认变量有了一些了解，你可以使用你的知识来确定何时检查，以及
何时在函数与可执行代码中赋值。深入理解了
Python
何时以何种方式定义对象，我们可以
确保这些“陷阱”类型不会给我们的代码添加
bug ...
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.