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What are some (concrete) use-cases for metaclasses?
...ate methods, than to do something like:
class PlottingInteractive:
add_slice = wrap_pylab_newplot(add_slice)
This method doesn't keep up with API changes and so on, but one that iterates over the class attributes in __init__ before re-setting the class attributes is more efficient and keeps t...
Or versus OrElse
...([0] object a,
[1] int32 b,
[2] bool CS$4$0000)
IL_0000: nop
IL_0001: ldnull
IL_0002: stloc.0
IL_0003: ldc.i4.3
IL_0004: stloc.1
IL_0005: ldloc.0
IL_0006: ldnull
IL_0007: ceq
IL_0009: ldloc.0
IL_000a: callvirt instance string [mscorlib]...
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 decorate a class?
...r specific scenario, YMMV :-)
What you're thinking of is a metaclass. The __new__ function in a metaclass is passed the full proposed definition of the class, which it can then rewrite before the class is created. You can, at that time, sub out the constructor for a new one.
Example:
def substitu...
What is __pycache__?
... it to bytecode first (this is an oversimplification) and stores it in the __pycache__ folder. If you look in there you will find a bunch of files sharing the names of the .py files in your project's folder, only their extensions will be either .pyc or .pyo. These are bytecode-compiled and optimized...
How to reliably open a file in the same directory as a Python script
...
I always use:
__location__ = os.path.realpath(
os.path.join(os.getcwd(), os.path.dirname(__file__)))
The join() call prepends the current working directory, but the documentation says that if some path is absolute, all other paths lef...
How to add property to a class dynamically?
...ibute, on a given class. Kinda like a way to factor a huge if tree out of __getattribute__.
When I ask for foo.b in the example above, Python sees that the b defined on the class implements the descriptor protocol—which just means it's an object with a __get__, __set__, or __delete__ method. Th...
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...
Relative imports in Python 2.7
...
Naming
When a file is loaded, it is given a name (which is stored in its __name__ attribute). If it was loaded as the top-level script, its name is __main__. If it was loaded as a module, its name is the filename, preceded by the names of any packages/subpackages of which it is a part, separated...
MySQL vs MongoDB 1000 reads
...nk of time.
foreach ($cursor as $obj)
{
//echo $obj["thread_title"] . "<br><Br>";
}
while the other chunk is spend yacking up a bunch of rand numbers.
function get_15_random_numbers()
{
$numbers = array();
for($i=1;$i<=15;$i++)
{
$numbers[] =...