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select、poll、epoll之间的区别总结[整理] - C/C++ - 清泛网 - 专注C/C++及内核技术
...1、select实现
select的调用过程如下所示：
（1）使用copy_from_user从用户空间拷贝fd_set到内核空间
（2）注册回调函数__pollwait
（3）遍历所有fd，调用其对应的poll方法（对于socket，这个poll方法是sock_poll，sock_poll根据情况会调用到...
List comprehension: Returning two (or more) items for each item
...bda x: x + 2
>>> g = lambda x: x ** 2
>>> list(chain.from_iterable((f(x), g(x)) for x in range(3)))
[2, 0, 3, 1, 4, 4]
Timings:
from timeit import timeit
f = lambda x: x + 2
g = lambda x: x ** 2
def fg(x):
yield f(x)
yield g(x)
print timeit(stmt='list(chain.from_itera...
How to export table as CSV with headings on Postgresql?
...
COPY products_273 TO '/tmp/products_199.csv' WITH (FORMAT CSV, HEADER);
as described in the manual.
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improve this answer
...
How do I access command line arguments in Python?
...a small example:
import argparse
parser = argparse.ArgumentParser("simple_example")
parser.add_argument("counter", help="An integer will be increased by 1 and printed.", type=int)
args = parser.parse_args()
print(args.counter + 1)
and the output for python prog.py -h
usage: simple_example [-h] ...
Python date string to date object
...<stdin>", line 1, in <module>
File "/usr/local/lib/python2.7/_strptime.py", line 308, in _strptime
format_regex = _TimeRE_cache.compile(format)
File "/usr/local/lib/python2.7/_strptime.py", line 265, in compile
return re_compile(self.pattern(format), IGNORECASE)
File "/usr/...
clear javascript console in Google Chrome
...
Chrome:
console._commandLineAPI.clear();
Safari:
console._inspectorCommandLineAPI.clear();
You can create your own variable, which works in both:
if (typeof console._commandLineAPI !== 'undefined') {
console.API = console._commandL...
What is the correct way to create a single-instance WPF application?
... NativeMethods.PostMessage(
(IntPtr)NativeMethods.HWND_BROADCAST,
NativeMethods.WM_SHOWME,
IntPtr.Zero,
IntPtr.Zero);
}
}
}
NativeMethods.cs
// this class just wraps some Win32 stuff that we're going to use...
How can we generate getters and setters in Visual Studio?
..., you will have to have an instance variable for it:
private PropertyType _property;
public PropertyType PropertyName
{
get
{
//logic here
return _property;
}
set
{
//logic here
_property = value;
}
}
Previous versions of Visual Studio al...
Calculating arithmetic mean (one type of average) in Python
...
Why have you called max?
– 1 -_-
Jul 25 '17 at 6:41
3
See the question abo...
What is the use of static variable in C#? When to use it? Why can't I declare the static variable in
...red. Let me explain this with an example:
class circle
{
public float _PI =3.14F;
public int Radius;
public funtionArea(int radius)
{
return this.radius * this._PI
}
}
class program
{
public static void main()
{
Circle c1 = new Cirle();
flo...