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Standard deviation of a list
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Since Python 3.4 / PEP450 there is a statistics module in the standard library, which has a method stdev for calculating the standard deviation of iterables like yours:
>>> A_rank = [0.8, 0.4, 1.2, 3.7, 2.6, 5.8]
>>> import statis...
Objective-C - Remove last character from string
...hat method you can trim your string like this:
if ([string length] > 0) {
string = [string substringToIndex:[string length] - 1];
} else {
//no characters to delete... attempting to do so will result in a crash
}
If you want a fancy way of doing this in just one line of code you...
What is the most efficient/elegant way to parse a flat table into a tree?
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Now that MySQL 8.0 supports recursive queries, we can say that all popular SQL databases support recursive queries in standard syntax.
WITH RECURSIVE MyTree AS (
SELECT * FROM MyTable WHERE ParentId IS NULL
UNION ALL
SELECT m.* F...
how to rotate a bitmap 90 degrees
There is a statement in android canvas.drawBitmap(visiblePage, 0, 0, paint);
10 Answers
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Does Python support short-circuiting?
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answered Apr 5 '10 at 18:20
Alex MartelliAlex Martelli
724k148148 gold badges11251125 silver badges13241324 bronze badges
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How can I initialize a String array with length 0 in Java?
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As others have said,
new String[0]
will indeed create an empty array. However, there's one nice thing about arrays - their size can't change, so you can always use the same empty array reference. So in your code, you can use:
private static final String[...
Hex representation of a color with alpha channel?
...se rgba() functional notation with decimals or percentages, e.g. rgba(255, 0, 0, 0.5) would be 50% transparent red. RGB channels are 0-255 or 0%-100%, alpha is 0-1.
In CSS 4*, you can specify the alpha channel using the 7th and 8th characters of an 8 digit hex colour, or 4th character of a 4 digit ...
How to find the sum of an array of numbers
... how can I find the sum of its elements? (In this case, the sum would be 10 .)
43 Answers
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(-2147483648> 0) returns true in C++?
... attempt using unsigned types to represent the value (for example, in C89/90 compilers were required to use unsigned long int, but not in C99 or C++). Implementations are allowed to do anything, since the behavior is undefined anyway.
As a side note, this is the reason why constants like INT_MIN ar...
In-memory size of a Python structure
...gt;>> import decimal
>>>
>>> d = {
... "int": 0,
... "float": 0.0,
... "dict": dict(),
... "set": set(),
... "tuple": tuple(),
... "list": list(),
... "str": "a",
... "unicode": u"a",
... "decimal": decimal.Decimal(0),
... "object": ob...