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In which case do you use the JPA @JoinTable annotation?
...ble named Task and add a foreign key column to the task table named project_id:
Project Task
------- ----
id id
name name
project_id
This way, it will be possible to determine the project for each row in the task table. If you use this approach, in your e...
Calling class staticmethod within the class body?
...
staticmethod objects apparently have a __func__ attribute storing the original raw function (makes sense that they had to). So this will work:
class Klass(object):
@staticmethod # use as decorator
def stat_func():
return 42
_ANS = stat_func...
Python __call__ special method practical example
I know that __call__ method in a class is triggered when the instance of a class is called. However, I have no idea when I can use this special method, because one can simply create a new method and perform the same operation done in __call__ method and instead of calling the instance, you can c...
Is there a simple, elegant way to define singletons? [duplicate]
...se the Instance method. Here's an example:
@Singleton
class Foo:
def __init__(self):
print 'Foo created'
f = Foo() # Error, this isn't how you get the instance of a singleton
f = Foo.instance() # Good. Being explicit is in line with the Python Zen
g = Foo.instance() # Returns already ...
How do I initialize the base (super) class?
... and invoke their base class through super(), e.g.
class X(object):
def __init__(self, x):
pass
def doit(self, bar):
pass
class Y(X):
def __init__(self):
super(Y, self).__init__(123)
def doit(self, foo):
return super(Y, self).doit(foo)
Because python knows about old- an...
STL中map容器使用自定义key类型报错详解 - C/C++ - 清泛网 - 专注C/C++及内核技术
...定义一个结构体来试试：[cpp]view plaincopystructa{char*pName;intm_a;} 引言
STL的map容器中，key的类型是不是随意的呢？
实践
编写测试代码
定义一个结构体来试试：
struct a
{
char* pName;
int m_a;
};
...
map<a, int> mp;
a ...
List all base classes in a hierarchy of given class?
...gt;
>>> import inspect
>>> inspect.getmro(B)
(<class '__main__.B'>, <class '__main__.A'>, <type 'object'>)
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Can a decorator of an instance method access the class?
...decorator, perhaps something like this (warning: untested code).
def class_decorator(cls):
for name, method in cls.__dict__.iteritems():
if hasattr(method, "use_class"):
# do something with the method and class
print name, cls
return cls
def method_decorator(v...
difference between variables inside and outside of __init__()
...
Variable set outside __init__ belong to the class. They're shared by all instances.
Variables created inside __init__ (and all other method functions) and prefaced with self. belong to the object instance.
...
What does “mro()” do?
...
Follow along...:
>>> class A(object): pass
...
>>> A.__mro__
(<class '__main__.A'>, <type 'object'>)
>>> class B(A): pass
...
>>> B.__mro__
(<class '__main__.B'>, <class '__main__.A'>, <type 'object'>)
>>> class C(A): pa...