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Why can't I use a list as a dict key in python?
..., with the hash as, say, their memory location?
It can be done without really breaking any of the requirements, but it leads to unexpected behavior. Lists are generally treated as if their value was derived from their content's values, for instance when checking (in-)equality. Many would - underst...
Finding the index of an item in a list
... complete. Some caveats about list.index follow. It is probably worth initially taking a look at the documentation for it:
list.index(x[, start[, end]])
Return zero-based index in the list of the first item whose value is equal to x. Raises a ValueError if there is no such item.
The optional argum...
What is an alternative to execfile in Python 3?
It seems they canceled in Python 3 all the easy way to quickly load a script by removing execfile()
12 Answers
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How do I catch a numpy warning like it's an exception (not just for testing)?
...ng: divide by zero encountered in divide
array([0])
>>> np.seterr(all='print')
{'over': 'warn', 'divide': 'warn', 'invalid': 'warn', 'under': 'ignore'}
>>> np.array([1])/0 #'print' mode
Warning: divide by zero encountered in divide
array([0])
This means that the warning you see...
Include all existing fields and add new fields to document
...t aggregation stage where I can instruct it to add a new field and include all existing fields, without having to list all the existing fields.
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如何获取IE (控件)的所有链接（包括Frameset, iframe） - C/C++ - 清泛网 -...
...（包括Frameset, iframe）IE 顶层 body 节点通过IHTMLElement->get_all 方法无法获取iframe 里面的节点列表：CComPtr<IHTMLElement> body;...CComPtr<IDispatc...IE 顶层 body 节点通过IHTMLElement->get_all 方法无法获取iframe 里面的节点列表：
CComPtr<IHTMLElement> b...
JavaScript: What are .extend and .prototype used for?
...ate ).lol() // alert message
In the snippet above, I define a method for all Date objects ( already existing ones and all new ones ).
extend is usually a high level function that copies the prototype of a new subclass that you want to extend from the base class.
So you can do something like:
e...
Does use of final keyword in Java improve the performance?
...
Usually not. For virtual methods, HotSpot keeps track of whether the method has actually been overridden, and is able to perform optimizations such as inlining on the assumption that a method hasn't been overridden - until it lo...
Where is my Django installation?
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Current top (accepted) answer works with my Ubuntu installation. As does yours. As do all of them!
– Adam Marshall
Apr 28 '14 at 14:24
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When should I use nil and NULL in Objective-C?
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technically, they are exactly equal, you can send messages to both nil and to NULL. Idiomatically though nil is usually used to represent an object
– cobbal
Oct 14 '09 at 5:43
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