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How to return an empty ActiveRecord relation?
If I have a scope with a lambda and it takes an argument, depending on the value of the argument, I might know that there will not be any matches, but I still want to return a relation, not an empty array:
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Django class-based view: How do I pass additional parameters to the as_view method?
...for the base class function where this is set .
– binithb
Nov 23 '15 at 16:57
In github.com/django/django/blob/master/...
“Private” (implementation) class in Python
...ls; "from module import *" does not import underscore-prefixed objects.
Edit: Reference to the single underscore convention
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[] and {} vs list() and dict(), which is better?
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In terms of speed, it's no competition for empty lists/dicts:
>>> from timeit import timeit
>>> timeit("[]")
0.040084982867934334
>>> timeit("list()")
0.17704233359267718
>>> timeit("{}")
0.03362019474542421...
In Python, what is the difference between “.append()” and “+= []”?
...ce as fast.
Python 3.0 (r30:67507, Dec 3 2008, 20:14:27) [MSC v.1500 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import timeit
>>> timeit.Timer('s.append("something")', 's = []').timeit()
0.20177424499999999
>>> tim...
What's the difference between SortedList and SortedDictionary?
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Yes - their performance characteristics differ significantly. It would probably be better to call them SortedList and SortedTree as that reflects the implementation more closely.
Look at the MSDN docs for each of them (SortedList, SortedDictionary) for details of the performance for di...
Remove Object from Array using JavaScript
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You can use several methods to remove item(s) from an Array:
//1
someArray.shift(); // first element removed
//2
someArray = someArray.slice(1); // first element removed
//3
someArray.splice(0, 1); // first element removed
//4
someArray.pop(); // last element re...
JavaScript Regular Expression Email Validation [duplicate]
... escaped, so instead of '\w' you should have '\\w'.
Alternatively, define it as a regular expression:
var pattern = /^\w+@[a-zA-Z_]+?\.[a-zA-Z]{2,3}$/;
BTW, please don't validate email addresses on the client-side. Your regular expression is way too simple to pass for a solid implementation a...
How do I clone a generic list in C#?
I have a generic list of objects in C#, and wish to clone the list. The items within the list are cloneable, but there doesn't seem to be an option to do list.Clone() .
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Difference between EXISTS and IN in SQL?
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The exists keyword can be used in that way, but really it's intended as a way to avoid counting:
--this statement needs to check the entire table
select count(*) from [table] where ...
--this statement is true as soon as one match is found
exists ( select * from [table] where...