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Creating a singleton in Python
... a base class. Here is a sample implementation:
class Singleton(type):
_instances = {}
def __call__(cls, *args, **kwargs):
if cls not in cls._instances:
cls._instances[cls] = super(Singleton, cls).__call__(*args, **kwargs)
return cls._instances[cls]
class...
Convert a python 'type' object to a string
...
print type(someObject).__name__
If that doesn't suit you, use this:
print some_instance.__class__.__name__
Example:
class A:
pass
print type(A())
# prints <type 'instance'>
print A().__class__.__name__
# prints A
Also, it seems th...
Can “using” with more than one resource cause a resource leak?
...Drawing]System.Drawing.Font font4,
[2] bool CS$4$0000
)
IL_0000: nop
IL_0001: ldstr "Arial"
IL_0006: ldc.r4 10
IL_000b: newobj instance void [System.Drawing]System.Drawing.Font::.ctor(string, float32)
IL_0010: stloc.0
.try
{
IL_0011: ldstr "Arial"
...
我的钢琴 · App Inventor 2 中文网
...经有什么
打开模板工程，你会看到：
一个 水平布局_琴键行（水平布局），里面已经放了 六个按钮：按钮_E 按钮_F 按钮_G 按钮_A 按钮_B 按钮_高C。
一个 音频播放器_音符（音频播放器组件），非可视组件，排在屏幕下方。
...
Why do we use __init__ in Python classes?
...ical piece of understanding: the difference between a class and an object. __init__ doesn't initialize a class, it initializes an instance of a class or an object. Each dog has colour, but dogs as a class don't. Each dog has four or fewer feet, but the class of dogs doesn't. The class is a concept o...
Relative paths in Python
..., you want to do something like this:
import os
dirname = os.path.dirname(__file__)
filename = os.path.join(dirname, 'relative/path/to/file/you/want')
This will give you the absolute path to the file you're looking for. Note that if you're using setuptools, you should probably use its package re...
Hashing a dictionary?
...d make a frozenset with the dict's items and use hash():
hash(frozenset(my_dict.items()))
This is much less computationally intensive than generating the JSON string or representation of the dictionary.
UPDATE: Please see the comments below, why this approach might not produce a stable result.
...
What is the difference between .*? and .* regular expressions?
...edy, first tries to match as many . as possible.
eeeAiiZuuuuAoooZeeee
\_______________/
A.* matched, Z can't match
Since the Z doesn't match, the engine backtracks, and .* must then match one fewer .:
eeeAiiZuuuuAoooZeeee
\______________/
A.* matched, Z still can't match
This ha...
iOS开发调试技巧总结 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...(format,...)do{\
fprintf(stderr,"%s\n",\
[[[NSStringstringWithUTF8String:__FILE__]lastPathComponent]UTF8String],\
__LINE__,__func__);\
(NSLog)((format),##__VA_ARGS__);\
fprintf(stderr,"-------\n");\
}while(0)
@interfaceViewController
@end
@implementationViewController
-(void)viewDi...
How to get the parents of a Python class?
...
Use the following attribute:
cls.__bases__
From the docs:
The tuple of base classes of a class
object.
Example:
>>> str.__bases__
(<type 'basestring'>,)
Another example:
>>> class A(object):
... pass
...
>>> ...