大约有 40,000 项符合查询结果（耗时：0.0486秒） [XML]
Create list of single item repeated N times
... mutable empty list, set, or dict, you should do something like this:
list_of_lists = [[] for _ in columns]
The underscore is simply a throwaway variable name in this context.
If you only have the number, that would be:
list_of_lists = [[] for _ in range(4)]
The _ is not really special, but y...
django - why is the request.POST object immutable?
...QueryDict class, which implements a full set of mutation methods including __setitem__, __delitem__, pop and clear. It implements immutability by checking a flag when you call one of the mutation methods. And when you call the copy method you get another QueryDict instance with the mutable flag turn...
How can I use getSystemService in a non-activity class (LocationManager)?
...
You can go for this :
getActivity().getSystemService(Context.CONNECTIVITY_SERVICE);
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Numeric for loop in Django templates
...onal context. Sometimes this comes in handy
{% for i in '0123456789'|make_list %}
{{ forloop.counter }}
{% endfor %}
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What is the volatile keyword useful for?
... volatile:
public class Singleton {
private static volatile Singleton _instance; // volatile variable
public static Singleton getInstance() {
if (_instance == null) {
synchronized (Singleton.class) {
if (_instance == null)
_instance = ...
Changing selection in a select with the Chosen plugin
...-selected", function() {
var locID = jQuery(this).attr('class').split('__').pop();
// I have a class name: class="result-selected locvalue__209"
var arrayCurrent = jQuery('#searchlocation').val();
var index = arrayCurrent.indexOf(locID);
if (index > -1) {
arrayCurrent....
Why Would I Ever Need to Use C# Nested Classes [duplicate]
...like this ...
class A
{
//used to help implement A
class B
{
A m_a;
internal B(A a) { m_a = a; }
...methods of B can access private members of the m_a instance...
}
...etc...
}
... and constructed from a method of A using code like this ...
//create an instance of B, whose ...
Standard deviation of a list
...calculating the standard deviation of iterables like yours:
>>> A_rank = [0.8, 0.4, 1.2, 3.7, 2.6, 5.8]
>>> import statistics
>>> statistics.stdev(A_rank)
2.0634114147853952
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How to set a Django model field's default value to a function call / callable (e.g., a date relative
..., timedelta
class MyModel(models.Model):
# default to 1 day from now
my_date = models.DateTimeField(default=datetime.now() + timedelta(days=1))
This last line is not defining a function; it is invoking a function to create a field in the class.
PRE Django 1.7
Django lets you pass a callable...
In CMake, how can I test if the compiler is Clang?
...
A reliable check is to use the CMAKE_<LANG>_COMPILER_ID variables. E.g., to check the C++ compiler:
if (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
# using Clang
elseif (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
# using GCC
elseif (CMAKE_CXX_COMPILER_ID STREQ...