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Principal component analysis in Python
...is 2 x 20. Dropping the primes,
d . Vt 2 principal vars = p.vars_pc( 20 vars )
U 1000 obs = p.pc_obs( 2 principal vars )
U . d . Vt 1000 obs, p.obs( 20 vars ) = pc_obs( vars_pc( vars ))
fast approximate A . vars, using the `npc` principal components
Ut ...
How to trigger event when a variable's value is changed?
...e you want to create a property.
public int MyProperty
{
get { return _myProperty; }
set
{
_myProperty = value;
if (_myProperty == 1)
{
// DO SOMETHING HERE
}
}
}
private int _myProperty;
This allows you to run some code any time the pr...
Callback functions in C++
...ard algorithms library <algorithm> use callbacks. For example the for_each algorithm applies an unary callback to every item in a range of iterators:
template<class InputIt, class UnaryFunction>
UnaryFunction for_each(InputIt first, InputIt last, UnaryFunction f)
{
for (; first != las...
Is there any difference between “foo is None” and “foo == None”?
...pares the same object instance
Whereas == is ultimately determined by the __eq__() method
i.e.
>>> class Foo(object):
def __eq__(self, other):
return True
>>> f = Foo()
>>> f == None
True
>>> f is None
False
...
Disable assertions in Python
...umentation:
An assert statement like this:
assert expression #, optional_message
Is equivalent to
if __debug__:
if not expression: raise AssertionError #(optional_message)
And,
the built-in variable __debug__ is True under normal circumstances, False when optimization is requested...
What is the most efficient way of finding all the factors of a number in Python?
...om functools import reduce
def factors(n):
return set(reduce(list.__add__,
([i, n//i] for i in range(1, int(n**0.5) + 1) if n % i == 0)))
This will return all of the factors, very quickly, of a number n.
Why square root as the upper limit?
sqrt(x) * sqrt(x) = x. So if t...
Use of #pragma in C
... == 7
Here's how you'd do the same thing in GCC:
struct PackedStructure __attribute__((__packed__))
{
char a;
int b;
short c;
};
// sizeof(PackedStructure == 7)
The GCC code is more portable, because if you want to compile that with a non-GCC compiler, all you have to do is
#define __att...
python design patterns [closed]
...for their existence.
It's nothing more than
class Null(object):
def __init__(self, *args, **kwargs):
"Ignore parameters."
return None
def __call__(self, *args, **kwargs):
"Ignore method calls."
return self
def __getattr__(self, mname):
"Ignore...
Python: Best way to add to sys.path relative to the current running script
...single line to each file, add a import statement at top e.g.
import import_my_lib
keep import_my_lib.py in bin and import_my_lib can correctly set the python path to whatever lib you want
share
|
...
Timeout function if it takes too long to finish [duplicate]
...nal
class TimeoutError(Exception):
pass
def timeout(seconds=10, error_message=os.strerror(errno.ETIME)):
def decorator(func):
def _handle_timeout(signum, frame):
raise TimeoutError(error_message)
def wrapper(*args, **kwargs):
signal.signal(signal.SI...