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Proper way to declare custom exceptions in modern Python?
... (or pass extra args), do this:
class ValidationError(Exception):
def __init__(self, message, errors):
# Call the base class constructor with the parameters it needs
super(ValidationError, self).__init__(message)
# Now for your custom code...
self.errors = erro...
How to run functions in parallel?
...starting'
for i in xrange(10000000): pass
print 'func2: finishing'
if __name__ == '__main__':
p1 = Process(target=func1)
p1.start()
p2 = Process(target=func2)
p2.start()
p1.join()
p2.join()
The mechanics of starting/joining child processes can easily be encapsulated into a functio...
How to detect reliably Mac OS X, iOS, Linux, Windows in C preprocessor? [duplicate]
... be found here.
Here is an example for gcc:
#if defined(WIN32) || defined(_WIN32) || defined(__WIN32__) || defined(__NT__)
//define something for Windows (32-bit and 64-bit, this part is common)
#ifdef _WIN64
//define something for Windows (64-bit only)
#else
//define something...
Get name of current class?
...
obj.__class__.__name__ will get you any objects name, so you can do this:
class Clazz():
def getName(self):
return self.__class__.__name__
Usage:
>>> c = Clazz()
>>> c.getName()
'Clazz'
...
How to mock an import
...importing A to get what you want:
test.py:
import sys
sys.modules['B'] = __import__('mock_B')
import A
print(A.B.__name__)
A.py:
import B
Note B.py does not exist, but when running test.py no error is returned and print(A.B.__name__) prints mock_B. You still have to create a mock_B.py where ...
Set Django IntegerField by choices=… name
...epresents the proper integer.
Like so:
LOW = 0
NORMAL = 1
HIGH = 2
STATUS_CHOICES = (
(LOW, 'Low'),
(NORMAL, 'Normal'),
(HIGH, 'High'),
)
Then they are still integers in the DB.
Usage would be thing.priority = Thing.NORMAL
...
Why does this loop produce “warning: iteration 3u invokes undefined behavior” and output more than 4
...e is the full assembly listing:
.file "a.cpp"
.section .text$_ZNKSt5ctypeIcE8do_widenEc,"x"
.linkonce discard
.align 2
LCOLDB0:
LHOTB0:
.align 2
.p2align 4,,15
.globl __ZNKSt5ctypeIcE8do_widenEc
.def __ZNKSt5ctypeIcE8do_widenEc; .scl 2; .type 32; .e...
What does the “at” (@) symbol do in Python?
...
Example
class Pizza(object):
def __init__(self):
self.toppings = []
def __call__(self, topping):
# When using '@instance_of_pizza' before a function definition
# the function gets passed onto 'topping'.
self.toppings.appe...
How to make a class JSON serializable
...f)
'{"fname": "/foo/bar"}'
In that case you can merely call json.dumps(f.__dict__).
If you want more customized output then you will have to subclass JSONEncoder and implement your own custom serialization.
For a trivial example, see below.
>>> from json import JSONEncoder
>>&g...
Accessing dict keys like an attribute?
...
The best way to do this is:
class AttrDict(dict):
def __init__(self, *args, **kwargs):
super(AttrDict, self).__init__(*args, **kwargs)
self.__dict__ = self
Some pros:
It actually works!
No dictionary class methods are shadowed (e.g. .keys() work just fine. Unle...