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How does the @property decorator work in Python?
...pecial descriptor object:
>>> property()
<property object at 0x10ff07940>
It is this object that has extra methods:
>>> property().getter
<built-in method getter of property object at 0x10ff07998>
>>> property().setter
<built-in method setter of property...
Python nonlocal statement
...
Compare this, without using nonlocal:
x = 0
def outer():
x = 1
def inner():
x = 2
print("inner:", x)
inner()
print("outer:", x)
outer()
print("global:", x)
# inner: 2
# outer: 1
# global: 0
To this, using nonlocal, where inner...
How is a CRC32 checksum calculated?
...eing it, but CRC32 seems either needlessly complicated, or insufficiently explained anywhere I could find on the web.
7 Ans...
Removing nan values from an array
...
If you're using numpy for your arrays, you can also use
x = x[numpy.logical_not(numpy.isnan(x))]
Equivalently
x = x[~numpy.isnan(x)]
[Thanks to chbrown for the added shorthand]
Explanation
The inner function, numpy.isnan returns a boolean/logical array which has the value...
When can I use a forward declaration?
...when you forward declare a type, all the compiler knows is that this type exists; it knows nothing about its size, members, or methods. This is why it's called an incomplete type. Therefore, you cannot use the type to declare a member, or a base class, since the compiler would need to know the layou...
Why is SSE scalar sqrt(x) slower than rsqrt(x) * x?
...
sqrtss gives a correctly rounded result. rsqrtss gives an approximation to the reciprocal, accurate to about 11 bits.
sqrtss is generating a far more accurate result, for when accuracy is required. rsqrtss exists for the cases when an approximation suffices, but speed is required. If ...
绘画动画组件 · App Inventor 2 中文网
...形精灵在其速度非零时是否移动。
方向
球形精灵 在 x 轴方向上以度数表示的方向，图示如下：
间隔
更新球形精灵位置的时间间隔（以毫秒为单位）。例如，如果间隔 为 50，速度 为 10，则球形精灵将每50毫秒移动10个...
What's the fastest way to convert String to Number in JavaScript?
...
There are 4 ways to do it as far as I know.
Number(x);
parseInt(x, 10);
parseFloat(x);
+x;
By this quick test I made, it actually depends on browsers.
http://jsperf.com/best-of-string-to-number-conversion/2
Implicit marked the fastest on 3 browsers, but it makes the code ...
Favicons - Best practices
...
Favicon is way more complex than what it sounds. 10 years ago, favicon.ico was the only needed item. Then, there was the touch icon, then multiple touch icons dues to the various iOS devices screen resolutions, then there was the tile icon for Windows...
Javascript reduce on array of objects
Say I want to sum a.x for each element in arr .
15 Answers
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