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Creating a singleton in Python
...Python asking a class what to do by calling __getattr__ when you reference one of it's attributes by doing myclass.attribute.
A metaclass essentially decides what the definition of a class means and how to implement that definition. See for example http://code.activestate.com/recipes/498149/, which ...
How do you remove all the options of a select box and then add one option and select it with jQuery?
...g core jQuery, how do you remove all the options of a select box, then add one option and select it?
24 Answers
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How can I rename a database column in a Ruby on Rails migration?
...a column, Rails 4 generates a change method instead of up and down as mentioned in the above section. The generated change method is:
$ > rails g migration ChangeColumnName
which will create a migration file similar to:
class ChangeColumnName < ActiveRecord::Migration
def change
ren...
Signed to unsigned conversion in C - is it always safe?
...e type of the operand with signed integer type.
In your case, we have one unsigned int (u) and signed int (i). Referring to (3) above, since both operands have the same rank, your i will need to be converted to an unsigned integer.
6.3.1.3 Signed and unsigned integers
When a value w...
Iterate two Lists or Arrays with one ForEach statement in C#
...omething like:
var numbers = new [] { 1, 2, 3, 4 };
var words = new [] { "one", "two", "three", "four" };
var numbersAndWords = numbers.Zip(words, (n, w) => new { Number = n, Word = w });
foreach(var nw in numbersAndWords)
{
Console.WriteLine(nw.Number + nw.Word);
}
As an alternative to...
Pandas selecting by label sometimes return Series, sometimes returns DataFrame
In Pandas, when I select a label that only has one entry in the index I get back a Series, but when I select an entry that has more then one entry I get back a data frame.
...
How to calculate moving average without keeping the count and data-total?
... want to average over.
Note that this approximation is equivalent to an exponential moving average.
See: Calculate rolling / moving average in C++
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Is there a better way to iterate over two lists, getting one element from each list for each iterati
I have a list of Latitudes and one of Longitudes and need to iterate over the latitude and longitude pairs.
7 Answers
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How to prevent column break within an element?
...le solution if you can avoid it.
UPDATE
According to the bug report mentioned above, Firefox 20+ supports page-break-inside: avoid as a mechanism for avoiding column breaks inside an element but the below code snippet demonstrates it still not working with lists:
.x {
column-count: 3;
...
What is the “N+1 selects problem” in ORM (Object-Relational Mapping)?
...hip.
Now, let's say you need to iterate through all the cars, and for each one, print out a list of the wheels. The naive O/R implementation would do the following:
SELECT * FROM Cars;
And then for each Car:
SELECT * FROM Wheel WHERE CarId = ?
In other words, you have one select for the Cars, and ...