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How can I access “static” class variables within class methods in Python?
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Why not just Foo.bar, instead of self.__class__.bar?
– mk12
Sep 13 '09 at 20:59
15
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Django in / not in query
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table1.objects.exclude(id__in=
table2.objects.filter(your_condition).values_list('id', flat=True))
The exclude function works like the Not operator you where asking for. The attribute flat = True tells to table2 query to return the value_list a...
How does the algorithm to color the song list in iTunes 11 work? [closed]
...table... looks like I reinvented the wheel a bit here)
convertToYUV[rawRGB_] :=
Module[{yuv},
yuv = {{0.299, 0.587, 0.114}, {-0.14713, -0.28886, 0.436},
{0.615, -0.51499, -0.10001}};
yuv . rawRGB
]
Next, I wrote a function to calculate color distance with the a...
Why use apparently meaningless do-while and if-else statements in macros?
...mi-colon. Should the user view code not needing one...
doSomething(1) ;
DO_SOMETHING_ELSE(2) // <== Hey? What's this?
doSomethingElseAgain(3) ;
This means the user expects the compiler to produce an error if the semi-colon is absent.
But the real real good reason is that at some time, the ma...
performSelector may cause a leak because its selector is unknown
... should simply be ignored, and it's easy to work around. Here's how:
if (!_controller) { return; }
SEL selector = NSSelectorFromString(@"someMethod");
IMP imp = [_controller methodForSelector:selector];
void (*func)(id, SEL) = (void *)imp;
func(_controller, selector);
Or more tersely (though hard...
Use cases for the 'setdefault' dict method
...ders -- some are optional, but you want defaults for them:
headers = parse_headers( msg ) # parse the message, get a dict
# now add all the optional headers
for headername, defaultvalue in optional_headers:
headers.setdefault( headername, defaultvalue )
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Read file from line 2 or skip header row
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Or use header_line = next(f).
– Samuel
Jan 6 '15 at 23:41
add a comment
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Rename Files and Directories (Add Prefix)
...ll work for filenames with spaces in them:
for f in * ; do mv -- "$f" "PRE_$f" ; done
("--" is needed to succeed with files that begin with dashes, whose names would otherwise be interpreted as switches for the mv command)
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Good reasons NOT to use a relational database?
... to use them instead of good-old relational databases? In my opinion, most applications rarely use the full power of SQL--it would be interesting to see how to build an SQL-free application.
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Is there a decorator to simply cache function return values?
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Starting from Python 3.2 there is a built-in decorator:
@functools.lru_cache(maxsize=100, typed=False)
Decorator to wrap a function with a memoizing callable that saves up to the maxsize most recent calls. It can save time when an expensive or I/O bound function is periodically called with th...