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Using @property versus getters and setters
...de world. There are plenty of ways to do this in Python (getattr, setattr, __getattribute__, etc..., but a very concise and clean one is:
def set_email(self, value):
if '@' not in value:
raise Exception("This doesn't look like an email address.")
self._email = value
def get_email(s...
The tilde operator in Python
...s operator.invert. To support this operator in your own class, give it an __invert__(self) method.
>>> import operator
>>> class Foo:
... def __invert__(self):
... print 'invert'
...
>>> x = Foo()
>>> operator.invert(x)
invert
>>> ~x
invert
Any ...
Python JSON serialize a Decimal object
...
The problem was that DecimalEncoder()._iterencode(decimal.Decimal('3.9')).next() returned the correct '3.9', but DecimalEncoder()._iterencode(3.9).next() returned a generator object which would only return '3.899...' when you piled on another .next(). Generator f...
Undefined reference to `pow' and `floor'
...
You can also use LD_PRELOAD to tell ld runtime linker to include libm.so in the memory map and symbol table of the process, so these symbols get loaded and everything works as expected
– debuti
May 28 '18 ...
How do I perform the SQL Join equivalent in MongoDB?
...ttps://docs.mongodb.org/master/reference/operator/aggregation/lookup/#pipe._S_lookup
From the docs:
{
$lookup:
{
from: <collection to join>,
localField: <field from the input documents>,
foreignField: <field from the documents of the "from" collection>...
capturing self strongly in this block is likely to lead to a retain cycle
...ng a weak reference to self before accessing timerDisp inside your block:
__weak typeof(self) weakSelf = self;
[player addPeriodicTimeObserverForInterval:CMTimeMakeWithSeconds(0.1, 100)
queue:nil
usingBlock:^(CMTime time) {
...
Behaviour of increment and decrement operators in Python
...so far as they don't explain what happens.
To be exact, +x evaluates to x.__pos__() and ++x to x.__pos__().__pos__().
I could imagine a VERY weird class structure (Children, don't do this at home!) like this:
class ValueKeeper(object):
def __init__(self, value): self.value = value
def __s...
error LNK2019: unresolved external symbol _WinMain@16 referenced in function ___tmainCRTStartup
...you can just hint at what your entry point is, because you haven't defined ___tmainCRTStartup. You can do this by adding the following to Properties -> Linker -> Command line:
/ENTRY:"mainCRTStartup"
This way you get rid of the console window.
...
How to run code when a class is subclassed? [duplicate]
...on2 you would define the metaclass of a class with
class SuperClass:
__metaclass__ = Watcher
where Watcher is a subclass of type.
In Python3 the syntax has been changed to
class SuperClass(metaclass=Watcher)
Both are equivalent to
Superclass = Watcher(name, bases, clsdict)
where in t...
How can I add reflection to a C++ application?
...re are some handy macros to help with typed expressions:
#define REM(...) __VA_ARGS__
#define EAT(...)
// Retrieve the type
#define TYPEOF(x) DETAIL_TYPEOF(DETAIL_TYPEOF_PROBE x,)
#define DETAIL_TYPEOF(...) DETAIL_TYPEOF_HEAD(__VA_ARGS__)
#define DETAIL_TYPEOF_HEAD(x, ...) REM x
#define DETAIL_TYP...