大约有 40,000 项符合查询结果（耗时：0.0232秒） [XML]
Scala: Nil vs List()
In Scala, is there any difference at all between Nil and List() ?
3 Answers
3
...
“x not in y” or “not x in y”
...am' not in 'spam and eggs'
>>> dis.dis(notin)
2 0 LOAD_CONST 1 ('ham')
3 LOAD_CONST 2 ('spam and eggs')
6 COMPARE_OP 7 (not in)
9 POP_TOP
10 LOAD_CONST 0 (...
How to get Scala List from Java List?
...now built into the language using:
import scala.collection.JavaConversions._
...
lst.toList.foreach{ node => .... }
works. asScala did not work
In 2.12.x use import scala.collection.JavaConverters._
In 2.13.x use import scala.jdk.CollectionConverters._
...
Deleting rows with MySQL LEFT JOIN
...ed May 4 '10 at 6:26
Daniel VassalloDaniel Vassallo
301k6666 gold badges475475 silver badges424424 bronze badges
...
Why can't yield return appear inside a try block with a catch?
...ty. I suspect there are very, very few times where this restriction is actually an issue that can't be worked around - but the added complexity in the compiler would be very significant.
There are a few things like this that I've already encountered:
Attributes not being able to be generic
Inabil...
How can I use threading in Python?
...ticle/blog post that you should definitely check out (no affiliation) - Parallelism in one line: A Better Model for Day to Day Threading Tasks. I'll summarize below - it ends up being just a few lines of code:
from multiprocessing.dummy import Pool as ThreadPool
pool = ThreadPool(4)
results = pool.m...
Is gcc std::unordered_map implementation slow? If so - why?
...2531
get : 1565
So std::unordered_map in gcc-4.7 is broken (or my installation, which is an installation of gcc-4.7.0 on Ubuntu - and another installation which is gcc 4.7.1 on debian testing).
I will submit a bug report.. until then: DO NOT use std::unordered_map with gcc 4.7!
...
SQLAlchemy: how to filter date field?
...In fact, your query is right except for the typo: your filter is excluding all records: you should change the <= for >= and vice versa:
qry = DBSession.query(User).filter(
and_(User.birthday <= '1988-01-17', User.birthday >= '1985-01-17'))
# or same:
qry = DBSession.query(User)....
MongoDB not equal to
...b.inventory.find( { price: { $not: { $gt: 1.99 } } } )
That would select all documents where:
The price field value is less than or equal to 1.99 or the price
Field does not exist
share
|
impro...
Is it bad practice to have a constructor function return a Promise?
...create and initialize a new instance. It should set up data structures and all instance-specific properties, but not execute any tasks. It should be a pure function without side effects if possible, with all the benefits that has.
What if I want to execute things from my constructor?
That shou...