大约有 8,000 项符合查询结果（耗时：0.0380秒） [XML]
How to test if list element exists?
... neval cld
"k" %in% names(foo) 467 933 1064.31 934 934 10730 100 a
is.null(foo[["k"]]) 0 0 168.50 1 467 3266 100 a
exists("k", where = foo) 6532 6998 7940.78 7232 7465 56917 100 b
If you are planing to use the list as a fast dictionary accessed many t...
Simple Digit Recognition OCR in OpenCV-Python
...corresponding digit key is pressed, it resizes this box to 10x10 and saves 100 pixel values in an array (here, samples) and corresponding manually entered digit in another array(here, responses).
Then save both the arrays in separate txt files.
At the end of manual classification of digits, all th...
Repository Pattern vs DAL
..."Repository," but a DAL. A contrived example in pseudo-code:
specification100 = new AccountHasMoreOrdersThan(100)
specification200 = new AccountHasMoreOrdersThan(200)
assert that specification200.isSpecialCaseOf(specification100)
specificationAge = new AccountIsOlderThan('2000-01-01')
combinedSp...
Set the table column width constant regardless of the amount of text in its cells?
In my table I set the width of the first cell in a column to be 100px .
However, when the text in one of the cell in this column is too long, the width of the column becomes more than 100px . How could I disable this expansion?
...
Why is iterating through a large Django QuerySet consuming massive amounts of memory?
... djangoapp.models import model
paginator = Paginator(model.objects.all(), 1000) # chunks of 1000, you can
# change this to desired chunk size
for page in range(1, paginator.num_pages + 1):
for row in paginator.page(page).object_list:
# ...
write a shell script to ssh to a remote machine and execute commands
...e; hostname -f'
If the file hosts.txt has a large number of entries, say 100, then the parallelism option may also be set to 100 to ensure that the commands are run concurrently:
pssh -i -h hosts.txt -p 100 -t 0 sleep 10000
Options:
-I: Read input and sends to each ssh process.
-P: Tells p...
Vertically centering a div inside another div [duplicate]
...nner {
position: absolute;
top: 50%;
left: 50%;
width: 100px;
height: 100px;
-webkit-transform: translate(-50%, -50%);
transform: translate(-50%, -50%);
background: red;
}
<div class="cn">
<div class="inner">
test
<...
Is Big O(logn) log base e?
... @Kinopiko: OK. I think we are saying the same thing. I would say O(100) = O(1) because O(100) = O(100 * 1) = O(C * 1) = O(1). Which is what I meant by constant expressions being superfluous. That is, the order of any constant is 1.
– Daniel Pryden
Oct...
Custom thread pool in Java 8 parallel stream
...parallelism", "20");
s.parallel().forEach(i -> {
try { Thread.sleep(100); } catch (Exception ignore) {}
System.out.print((System.currentTimeMillis() - start) + " ");
});
The output is:
215 216 216 216 216 216 216 216 315 316 316 316 316 316 316 316 415 416 416 416
So you can see t...
When should I use Struct vs. OpenStruct?
...
Other benchmark:
require 'benchmark'
require 'ostruct'
REP = 100000
User = Struct.new(:name, :age)
USER = "User".freeze
AGE = 21
HASH = {:name => USER, :age => AGE}.freeze
Benchmark.bm 20 do |x|
x.report 'OpenStruct slow' do
REP.times do |index|
OpenStruct.new(:na...