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Get last result in interactive Python shell
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Underscore.
>>> 5+5
10
>>> _
10
>>> _ + 5
15
>>> _
15
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Using OR in SQLAlchemy
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From the tutorial:
from sqlalchemy import or_
filter(or_(User.name == 'ed', User.name == 'wendy'))
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How to merge lists into a list of tuples?
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In Python 2:
>>> list_a = [1, 2, 3, 4]
>>> list_b = [5, 6, 7, 8]
>>> zip(list_a, list_b)
[(1, 5), (2, 6), (3, 7), (4, 8)]
In Python 3:
>>> list_a = [1, 2, 3, 4]
>>> list_b = [5, 6, 7, 8]
>>> list(zi...
Average of 3 long integers
...ng divide by constants technique from hacker's delight
public class int128_t {
private int H;
private long L;
public int128_t(int h, long l)
{
H = h;
L = l;
}
public int128_t add(int128_t a)
{
int128_t s;
s.L = L + a.L;
s.H = H +...
How to achieve function overloading in C?
...rt for function overloading (not operators), thanks to the addition of the _Generic keyword in C11. (supported in GCC since version 4.9)
(Overloading isn't truly "built-in" in the fashion shown in the question, but it's dead easy to implement something that works like that.)
_Generic is a compile-...
Best practice for Python assert
...essThanZeroException(Exception):
pass
class variable(object):
def __init__(self, value=0):
self.__x = value
def __set__(self, obj, value):
if value < 0:
raise LessThanZeroException('x is less than zero')
self.__x = value
def __get__(self, o...
How to add an integer to each element in a list?
...
new_list = [x+1 for x in my_list]
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Xcode doesn't show the line that causes a crash
...rminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSSingleObjectArrayI objectAtIndex:]: index 1 beyond bounds [0 .. 0]'
*** First throw call stack:
(
0 CoreFoundation 0x000000010e85cd4b __exceptionPreprocess + 171
1 libobjc.A.dylib ...
Best way to require all files from a directory in ruby?
... (e.g. you want to load all files in the lib directory):
Dir[File.dirname(__FILE__) + '/lib/*.rb'].each {|file| require file }
Edit: Based on comments below, an updated version:
Dir[File.join(__dir__, 'lib', '*.rb')].each { |file| require file }
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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 ...