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Best practices for circular shift (rotate) operations in C++
...,7 which is slower and takes more bytes than rol edi,7 on some CPUs (especially AMD, but also some Intel), when BMI2 isn't available for rorx eax,edi,25 to save a MOV.
MSVC: x86-64 CL19: Only recognized for constant-count rotates. (The wikipedia idiom is recognized, but the branch and AND aren't op...
Fastest way to get the first object from a queryset in django?
...eturn None if there aren't any. There are lots of ways to do this which all work. But I'm wondering which is the most performant.
...
Merge PDF files
...iles, output_stream):
input_streams = []
try:
# First open all the files, then produce the output file, and
# finally close the input files. This is necessary because
# the data isn't read from the input files until the write
# operation. Thanks to
# h...
Python __str__ versus __unicode__
...onfusing, but in 2.x we're stuck with them for compatibility reasons. Generally, you should put all your string formatting in __unicode__(), and create a stub __str__() method:
def __str__(self):
return unicode(self).encode('utf-8')
In 3.0, str contains characters, so the same methods are nam...
Explaining Python's '__enter__' and '__exit__'
...
Using these magic methods (__enter__, __exit__) allows you to implement objects which can be used easily with the with statement.
The idea is that it makes it easy to build code which needs some 'cleandown' code executed (think of it as a try-finally block). Some more ex...
How to make a class property? [duplicate]
...az.bar == 50
assert foo.bar == 50
The setter didn't work at the time we call Bar.bar, because we are calling
TypeOfBar.bar.__set__, which is not Bar.bar.__set__.
Adding a metaclass definition solves this:
class ClassPropertyMetaClass(type):
def __setattr__(self, key, value):
if key ...
Difference between abstract class and interface in Python
... @L.DeLeo - are you sure your notion of has-a vs. is-a is correct? I generally view the distinction as has-a = member variable vs. is-a = inheritance (parent class or interface). Think Comparable or List in Java; those are is-a relationships, regardless of whether they're interfaces or abstract cl...
Exporting functions from a DLL with dllexport
...ain C exports, use a C project not C++. C++ DLLs rely on name-mangling for all the C++isms (namespaces etc...). You can compile your code as C by going into your project settings under C/C++->Advanced, there is an option "Compile As" which corresponds to the compiler switches /TP and /TC.
If you ...
Python multiprocessing pool.map for multiple arguments
...rmap method, which accepts a sequence of argument tuples. It then automatically unpacks the arguments from each tuple and passes them to the given function:
import multiprocessing
from itertools import product
def merge_names(a, b):
return '{} & {}'.format(a, b)
if __name__ == '__main__':...
Can I create links with 'target=“_blank”' in Markdown?
...rget="_blank">Hello, world!</a>
Most Markdown engines I've seen allow plain old HTML, just for situations like this where a generic text markup system just won't cut it. (The StackOverflow engine, for example.) They then run the entire output through an HTML whitelist filter, regardless, ...