大约有 19,000 项符合查询结果（耗时：0.0725秒） [XML]
Why is it slower to iterate over a small string than a small list?
...sions. I'll examine the compiled code.
For Python 3:
import dis
def list_iterate():
[item for item in ["a", "b", "c"]]
dis.dis(list_iterate)
#>>> 4 0 LOAD_CONST 1 (<code object <listcomp> at 0x7f4d06b118a0, file "", line 4>)
#>>> ...
Pragma in define macro
...
If you're using c99 or c++0x there is the pragma operator, used as
_Pragma("argument")
which is equivalent to
#pragma argument
except it can be used in macros (see section 6.10.9 of the c99 standard, or 16.9 of the c++0x final committee draft)
For example,
#define STRINGIFY(a) #a
#def...
How to extract the decision rules from scikit-learn decision-tree?
...wer is more correct than the other answers here:
from sklearn.tree import _tree
def tree_to_code(tree, feature_names):
tree_ = tree.tree_
feature_name = [
feature_names[i] if i != _tree.TREE_UNDEFINED else "undefined!"
for i in tree_.feature
]
print "def tree({}):"....
Open link in new tab or window [duplicate]
...
You should add the target="_blank" and rel="noopener noreferrer" in the anchor tag.
For example:
<a target="_blank" rel="noopener noreferrer" href="http://your_url_here.html">Link</a>
Adding rel="noopener noreferrer" is not mandatory, b...
Detecting request type in PHP (GET, POST, PUT or DELETE)
...
By using
$_SERVER['REQUEST_METHOD']
Example
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
// The request is using the POST method
}
For more details please see the documentation for the $_SERVER variable.
...
Why doesn't list have safe “get” method like dictionary?
...f your list).
Of course, you can easily implement this yourself:
def safe_list_get (l, idx, default):
try:
return l[idx]
except IndexError:
return default
You could even monkeypatch it onto the __builtins__.list constructor in __main__, but that would be a less pervasive change since...
Any way to properly pretty-print ordered dictionaries?
...well if you don't care about the order of the keys. Personally, I wish the __repr__ for OrderedDict would produce output like this but preserve the order of the keys.
– ws_e_c421
Sep 24 '15 at 15:54
...
Xcode doesn't show the line that causes a crash
...rminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSSingleObjectArrayI objectAtIndex:]: index 1 beyond bounds [0 .. 0]'
*** First throw call stack:
(
0 CoreFoundation 0x000000010e85cd4b __exceptionPreprocess + 171
1 libobjc.A.dylib ...
Getter and Setter?
...
You can use php magic methods __get and __set.
<?php
class MyClass {
private $firstField;
private $secondField;
public function __get($property) {
if (property_exists($this, $property)) {
return $this->$property;
}
}
publi...
C# Lazy Loaded Automatic Properties
... 4.0 Lazy<T> type to create this pattern
private Lazy<string> _someVariable =new Lazy<string>(SomeClass.IOnlyWantToCallYouOnce);
public string SomeVariable => _someVariable.Value;
This code will lazily calculate the value of _someVariable the first time the Value expression i...