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mongodb group values by multiple fields
... $slice just off the basic aggregation result. For "large" results, run parallel queries instead for each grouping ( a demonstration listing is at the end of the answer ), or wait for SERVER-9377 to resolve, which would allow a "limit" to the number of items to $push to an array.
db.books.aggregate(...
What does the JSLint error 'body of a for in should be wrapped in an if statement' mean?
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First of all, never use a for in loop to enumerate over an array. Never. Use good old for(var i = 0; i<arr.length; i++).
The reason behind this is the following: each object in JavaScript has a special field called prototype. Ever...
How to sort an IEnumerable
How can I sort an IEnumerable<string> alphabetically. Is this possible?
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Is it alright to use target=“_blank” in HTML5?
I recall reading somewhere that in HTML5 it was no longer okay to use target="_blank" in HTML5, but I can't find it now.
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IOCTL Linux device driver [closed]
...l, which means "input-output control" is a kind of device-specific system call. There are only a few system calls in Linux (300-400), which are not enough to express all the unique functions devices may have. So a driver can define an ioctl which allows a userspace application to send it orders. How...
In MySQL, can I copy one row to insert into the same table?
...an existing row in the table) but I want to do this without having to list all the columns after the "select", because this table has too many columns.
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Using PUT method in HTML form
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XHTML 1.x forms only support GET and POST. GET and POST are the only allowed values for
the "method" attribute.
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How to import a Python class that is in a directory above?
...on __file__ to find out the parent directory (a couple of os.path.dirname calls will do;-), then (if that directory is not already on sys.path) prepend temporarily insert said dir at the very start of sys.path, __import__, remove said dir again -- messy work indeed, but, "when you must, you must" (a...
Encoding an image file with base64
... here is an update after you have edited your original question.
First of all, remember to use raw strings (prefix the string with 'r') when using path delimiters on Windows, to prevent accidentally hitting an escape character. Second, PIL's Image.open either accepts a filename, or a file-like (tha...
Building a minimal plugin architecture in Python
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Mine is, basically, a directory called "plugins" which the main app can poll and then use imp.load_module to pick up files, look for a well-known entry point possibly with module-level config params, and go from there. I use file-monitorin...