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What is the difference between ${var}, “$var”, and “${var}” in the Bash shell?
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Braces ($var vs. ${var})
In most cases, $var and ${var} are the same:
var=foo
echo $var
# foo
echo ${var}
# foo
The braces are only needed to resolve ambiguity in expressions:
var=foo
echo $varbar
# Prints nothing because there is no variable 'varbar'
echo ${var}bar...
In javascript, is an empty string always false as a boolean?
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Yes. Javascript is a dialect of ECMAScript, and ECMAScript language specification clearly defines this behavior:
ToBoolean
The result is false if the argument is the empty String (its length is zero);
otherwise the result is true
Quote taken from http://www.ecma-inte...
How does numpy.histogram() work?
...ere are 3 bins, for values ranging from 0 to 1 (excl 1.), 1 to 2 (excl. 2) and 2 to 3 (incl. 3), respectively. The way Numpy defines these bins if by giving a list of delimiters ([0, 1, 2, 3]) in this example, although it also returns the bins in the results, since it can choose them automatically f...
Set scroll position
...ll an element instead of the full window, elements don't have the scrollTo and scrollBy methods. You should:
var el = document.getElementById("myel"); // Or whatever method to get the element
// To set the scroll
el.scrollTop = 0;
el.scrollLeft = 0;
// To increment the scroll
el.scrollTop += 100;...
URL query parameters to dict python
Is there a way to parse a URL (with some python library) and return a python dictionary with the keys and values of a query parameters part of the URL?
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How to save a BufferedImage as a File
...atName is the String containing the informal name of the format (e.g. png) and output is the file object to be written to. An example usage of the method for PNG file format is shown below:
ImageIO.write(image, "png", file);
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Multiple aggregations of the same column using pandas GroupBy.agg()
Is there a pandas built-in way to apply two different aggregating functions f1, f2 to the same column df["returns"] , without having to call agg() multiple times?
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jQuery / Javascript - How do I convert a pixel value (20px) to a number value (20)
... answered Jun 11 '10 at 15:31
Andy EAndy E
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postgresql COUNT(DISTINCT …) very slow
...ount int not null), using triggers. But your write performance will suffer and if you update multiple x values in single transaction then you'd need to do this in some explicit order to avoid possible deadlock.
share
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Get ffmpeg information in friendly way
...t information you want it to display (with the -show_format, -show_packets and -show_streams options) or it'll just give you blank output (like you mention in one of your comments).
For example, ffprobe -v quiet -print_format json -show_format -show_streams somefile.asf would yield something like t...