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Why doesn't Python have a sign function?
I can't understand why Python doesn't have a sign function. It has an abs builtin (which I consider sign 's sister), but no sign .
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Is there a printf converter to print in binary format?
I can print with printf as a hex or octal number. Is there a format tag to print as binary, or arbitrary base?
52 Answer...
How can I use map and receive an index as well in Scala?
Is there any List/Sequence built-in that behaves like map and provides the element's index as well?
8 Answers
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Why can't non-default arguments follow default arguments?
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All required parameters must be placed before any default arguments. Simply because they are mandatory, whereas default arguments are not. Syntactically, it would be impossible for the interpreter to decide which values match which arguments if mixed mod...
Finish an activity from another activity
...When the user clicks modify, call the new Intent or simply finish activity B.
FIRST WAY
In your first activity, declare one Activity object like this,
public static Activity fa;
onCreate()
{
fa = this;
}
now use that object in another Activity to finish first-activity like this,
onCreate(...
Element-wise addition of 2 lists?
...>> %timeit from operator import add;map(add, list1, list2)
10 loops, best of 3: 44.6 ms per loop
>>> %timeit from itertools import izip; [a + b for a, b in izip(list1, list2)]
10 loops, best of 3: 71 ms per loop
>>> %timeit [a + b for a, b in zip(list1, list2)]
10 loops, best...
Is it better to call ToList() or ToArray() in LINQ queries?
...ase where I want to eval a query right where I declare it. This is usually because I need to iterate over it multiple times and it is expensive to compute. For example:
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How to select an element with 2 classes [duplicate]
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You can chain class selectors without a space between them:
.a.b {
color: #666;
}
Note that, if it matters to you, IE6 treats .a.b as .b, so in that browser both div.a.b and div.b will have gray text. See this answer for a comparison between proper browsers and I...
Python if-else short-hand [duplicate]
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The most readable way is
x = 10 if a > b else 11
but you can use and and or, too:
x = a > b and 10 or 11
The "Zen of Python" says that "readability counts", though, so go for the first way.
Also, the and-or trick will fail if ...
scrapy xpath抓取节点的文本innerText、innerHTML、outerHTML - 更多技术 -...
...取节点的文本innerText、innerHTML、outerHTML假设抓取：<p> xx<b>x< b>< p> 抓取p节点本身，得到的内容：<p>xx<b>x< b>< p>response xpath(& 39; div[@class="question"] div[2] div[2] div[1] p[1]& 39;) extract() 抓 假设抓取：
<p>
xx<b>x</b>
</p>
scrapy代码：
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