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Creating the Singleton design pattern in PHP5
...ctor so nobody else can instantiate it
*
*/
private function __construct()
{
}
}
To use:
$fact = UserFactory::Instance();
$fact2 = UserFactory::Instance();
$fact == $fact2;
But:
$fact = new UserFactory()
Throws an error.
See http://php.net/manual/en/language.variable...
enum - getting value of enum on string conversion
...;>> member.name
'red'
>>> member.value
1
You could add a __str__ method to your enum, if all you wanted was to provide a custom string representation:
class D(Enum):
def __str__(self):
return str(self.value)
x = 1
y = 2
Demo:
>>> from enum import E...
hidden symbol ... is referenced by DSO 剖析 - C/C++ - 清泛网 - 专注C/C++及内核技术
...因是符号(函数)未导出导致的，添加导出申明即可解决：__attribute__ ((visibility("default")) DSO 是动态共享对象，Linux报“hidden symbol ... is referenced by DSO”错误的原因是符号(函数)未导出导致的，添加导出申明即可解决：
__attribute__ (...
C++简练易用的线程池(threadpool)及上下文隔离的无锁线程池(isolated_threa...
...易用的线程池(threadpool)及上下文隔离的无锁线程池(isolated_threadpool)完整实现本文主要介绍两种C++线程池模型完整代码，经过实战考验的，效率已极致优化的代码，可直接用于实际项目开发。1、C++简练易用的线程池(threadpool)
完整...
How can I implement a tree in Python?
...s easy to create. For example, a binary tree might be:
class Tree:
def __init__(self):
self.left = None
self.right = None
self.data = None
You can use it like this:
root = Tree()
root.data = "root"
root.left = Tree()
root.left.data = "left"
root.right = Tree()
root.right...
Change auto increment starting number?
In MySQL, I have a table, and I want to set the auto_increment value to 5 instead of 1 . Is this possible and what query statement does this?
...
Checking images for similarity with OpenCV
...e the L2 relative error between images.
double errorL2 = norm( A, B, CV_L2 );
// Convert to a reasonable scale, since L2 error is summed across all pixels of the image.
double similarity = errorL2 / (double)( A.rows * A.cols );
return similarity;
}
else {
//Images have a differen...
How can I read a function's signature including default argument values?
...
@darth_coder: In Python2, getargspec raises TypeError if the input is not recognized as a Python function -- that is, a function implemented in Python. In CPython, Exception.__init__ is implemented in C, hence the TypeError. You'll...
Python nested functions variable scoping [duplicate]
...When I run your code I get this error:
UnboundLocalError: local variable '_total' referenced before assignment
This problem is caused by this line:
_total += PRICE_RANGES[key][0]
The documentation about Scopes and Namespaces says this:
A special quirk of Python is that – if no global st...
What does a type followed by _t (underscore-t) represent?
... with the Stack Overflow search or Google. What does a type followed by a _t mean? Such as
10 Answers
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