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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[...
Accessing UI (Main) Thread safely in WPF
... example:
class MyViewModel
{
private readonly SynchronizationContext _syncContext;
public MyViewModel()
{
// we assume this ctor is called from the UI thread!
_syncContext = SynchronizationContext.Current;
}
// ...
private void watcher_Changed(object send...
Iterating over all the keys of a map
...
how do I iterate over all the keys?
Use the accepted answer:
for k, _ := range m { ... }
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What does `dword ptr` mean?
...ral purpose computers usually use 32 or 64 bits. en.wikipedia.org/wiki/Word_(computer_architecture)
– uzay95
Dec 25 '16 at 21:35
6
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How to check for file existence [duplicate]
Is there a Ruby class/method where I could pass "a full path", home/me/a_file.txt , to identify whether it is a valid file path?
...
I want to use CASE statement to update some records in sql server 2005
...N 44
ELSE 0
END AS [CycleId]
INTO
##ACE1_PQPANominals_1
FROM
[dbo].[ProductionQueueProcessAutoclaveNominals]
WHERE
[QueueId] = 3
ORDER BY
[BaseDimensionId], [ElastomerTypeId], [Id];
---- (403 row(s) affected)
UPDATE [dbo].[ProductionQueueProcessAutoc...
解决：ORA-00054:资源正忙,要求指定NOWAIT - 数据库(内核) - 清泛网 - 专注...
...出所有被锁的对象，定位出哪个回话占用
select l.session_id,o.owner,o.object_name from v$locked_object l,dba_objects o where l.object_id=o.object_id
结果：
session_id owner object_name
158 SA TEST_1
...
对比想要创建的索引，定位哪些会话需要被删除
2：...
如何查看Android应用.apk是32位还是64位？ - App应用开发 - 清泛IT社区，为创新赋能！
...APK文件的信息，包括其支持的架构。
aapt dump badging your_app.apk | grep native-code
这条命令会输出APK支持的架构信息。aapt工具包含在Android SDK的Build-tools中。
请注意，如果一个APK支持多个架构，那么它会被认为是兼容的，因为And...
How to loop through a plain JavaScript object with the objects as members?
...
for (var key in validation_messages) {
// skip loop if the property is from prototype
if (!validation_messages.hasOwnProperty(key)) continue;
var obj = validation_messages[key];
for (var prop in obj) {
// skip loop if the prop...
How to read a large file - line by line?
...object, Python looks up in the list of object methods a special one called __iter__, which tells it what to do. File objects define this special method to return an iterator over the lines. (Roughly.)
– Katriel
Feb 10 '15 at 12:14
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