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Difference between Django's annotate and aggregate methods?
... in the queryset.
Aggregation
>>> Book.objects.aggregate(average_price=Avg('price'))
{'average_price': 34.35}
Returns a dictionary containing the average price of all books in the queryset.
Annotation
>>> q = Book.objects.annotate(num_authors=Count('authors'))
>>> q[...
What is the difference between “def” and “val” to define a function
...ion every time (new instance of Function1).
def even: Int => Boolean = _ % 2 == 0
even eq even
//Boolean = false
val even: Int => Boolean = _ % 2 == 0
even eq even
//Boolean = true
With def you can get new function on every call:
val test: () => Int = {
val r = util.Random.nextInt
...
Is “inline” without “static” or “extern” ever useful in C99?
...e behavior is the same as if the call were made to another function, say
__func, with internal linkage. A conforming program must not depend on which function is
called. This is the inline model in the Standard.
A conforming program must not rely on the implementation using the inline defin...
Event handling for iOS - how hitTest:withEvent: and pointInside:withEvent: are related?
...eturn self;
}
return nil;
}
Edit Swift 4:
override func hitTest(_ point: CGPoint, with event: UIEvent?) -> UIView? {
if self.point(inside: point, with: event) {
return super.hitTest(point, with: event)
}
guard isUserInteractionEnabled, !isHidden, alpha > 0 else {...
Python append() vs. + operator on lists, why do these give different results?
...ut answering the questions asked? People ask why PHP is called PHP and why __lt__ could not be overloaded in Python (nowadays it can). Why-questions are the most essential ones but often the trickiest to answer: they ask for the essence, not for a pointer to the manual. And of course: if you dislike...
How do you read a file into a list in Python? [duplicate]
...
The pythonic way to read a file and put every lines in a list:
from __future__ import with_statement #for python 2.5
with open('C:/path/numbers.txt', 'r') as f:
lines = f.readlines()
Then, assuming that each lines contains a number,
numbers =[int(e.strip()) for e in lines]
...
Recursive lambda functions in C++11
...r, not by capture.
const auto sum = [term,next](int a, int b) {
auto sum_impl=[term,next](int a,int b,auto& sum_ref) mutable {
if(a>b){
return 0;
}
return term(a) + sum_ref(next(a),b,sum_ref);
};
return sum_impl(a,b,sum_impl);
};
All problems in computer science can...
Ant task to run an Ant target only if a file exists?
...
Check Using Filename filters like DB_*/**/*.sql
Here is a variation to perform an action if one or more files exist corresponding to a wildcard filter. That is, you don't know the exact name of the file.
Here, we are looking for "*.sql" files in any sub-dire...
Windows下 C++网络延时检测 - C/C++ - 清泛网 - 专注C/C++及内核技术
...现的呢？直接上代码吧，亲测可用：
Ping.h
#ifndef CPING_H
#define CPING_H
#include <windows.h>
#include <conio.h>
#include <winnt.h>
#define PING_TIMES 2 //ping 4 次
typedef struct _IPINFO
{
unsigned char Ttl; // Time To Live
unsigned char Tos; // Type Of Se...
Use didSelectRowAtIndexPath or prepareForSegue method for UITableView?
...() contains the correct value when prepareFroSegue... is called: tableView(_:didSelectrowAtIndexPath:) isn't called until later.
– Nicolas Miari
Jun 7 '16 at 2:21
add a commen...