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If vs. Switch Speed
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answered Jan 14 '09 at 23:16
Konrad RudolphKonrad Rudolph
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App Inventor 2 数学代码块 · App Inventor 2 中文网
... ( ^ )
返回第一个数字的第二个数字次幂的结果。比如2^3 = 222 = 8
随机整数 (random integer)
返回给定值之间（包含首尾）的随机整数值。参数的顺序不限，也就是 1~100 和 100~1 效果一样。
随机小数 (random fraction)
返回 0 到 1 ...
How can I obtain the element-wise logical NOT of a pandas Series?
... True, False, True])
In [8]: ~s
Out[8]:
0 False
1 False
2 True
3 False
dtype: bool
Using Python2.7, NumPy 1.8.0, Pandas 0.13.1:
In [119]: s = pd.Series([True, True, False, True]*10000)
In [10]: %timeit np.invert(s)
10000 loops, best of 3: 91.8 µs per loop
In [11]: %timeit ~s
10...
Using async/await for multiple tasks
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int[] ids = new[] { 1, 2, 3, 4, 5 };
Parallel.ForEach(ids, i => DoSomething(1, i, blogClient).Wait());
Although you run the operations in parallel with the above code, this code blocks each thread that each operation runs on. For example, if the ...
Regular expression to match DNS hostname or IP Address?
...lidIpAddressRegex = "^(([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])$";
ValidHostnameRegex = "^(([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\-]*[a-zA-Z0-9])\.)*([A-Za-z0-9]|[A-Za-z0-9][A-Za-z0-9\-]*[A-Za-z0-9])$";
ValidIpAddressRegex matches valid IP...
Why does changing 0.1f to 0 slow down performance by 10x?
...) {
double start = omp_get_wtime();
const float x[16]={1.1,1.2,1.3,1.4,1.5,1.6,1.7,1.8,1.9,2.0,2.1,2.2,2.3,2.4,2.5,2.6};
const float z[16]={1.123,1.234,1.345,156.467,1.578,1.689,1.790,1.812,1.923,2.034,2.145,2.256,2.367,2.478,2.589,2.690};
float y[16];
for(int i=0;i<16;i++)
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Programmatically Lighten or Darken a hex color (or rgb, and blend colors)
...n or darken a hex color by a specific amount. Just pass in a string like "3F6D2A" for the color ( col ) and a base10 integer ( amt ) for the amount to lighten or darken. To darken, pass in a negative number (i.e. -20 ).
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Get a random boolean in python?
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349
Adam's answer is quite fast, but I found that random.getrandbits(1) to be quite a lot faster. ...
Apply multiple functions to multiple groupby columns
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313
The second half of the currently accepted answer is outdated and has two deprecations. First a...
How to validate an Email in PHP?
... Manual should suffice.
Update 1: As pointed out by @binaryLV:
PHP 5.3.3 and 5.2.14 had a bug related to
FILTER_VALIDATE_EMAIL, which resulted in segfault when validating
large values. Simple and safe workaround for this is using strlen()
before filter_var(). I'm not sure about 5.3.4 fin...