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django: BooleanField, how to set the default value to true?
...fields/#django.forms.Field.initial ) like
class MyForm(forms.Form):
my_field = forms.BooleanField(initial=True)
If you're using a ModelForm, you can set a default value on the model field ( https://docs.djangoproject.com/en/2.2/ref/models/fields/#default ), which will apply to the resulting M...
The order of elements in Dictionary
...when enumerating them:
foreach (KeyValuePair<string, string> kvp in _Dictionary.OrderBy(k => k.Value)) {
...
}
In framework 2.0 you would first have to put the items in a list in order to sort them:
List<KeyValuePair<string, string>> items = new List<KeyValuePair<str...
Resolve Type from Class Name in a Different Assembly
...pe>
{
private static Dictionary<string, Type> _types;
private static object _lock = new object();
public static Type FromString(string typeName)
{
if (_types == null) CacheTypes();
if (_types.ContainsK...
How to initialize a vector in C++ [duplicate]
... give you the beginning and end of an array:
template <typename T, size_t N>
T* begin(T(&arr)[N]) { return &arr[0]; }
template <typename T, size_t N>
T* end(T(&arr)[N]) { return &arr[0]+N; }
And then you can do this without having to repeat the size all over:
int vv[]...
use of deleted function std::unique_ptr 编译错误剖析，你可能少了一个st...
use of deleted function std::unique_ptr 编译错误剖析，你可能少了一个std::move编译报错日志如下： usr include c++ 4 7 bits stl_construct h:77:7: error: use of deleted function & 39;std::unique_ptr<_Tp, _Dp>::unique_ptr(const std::unique_p 编译报错日志如下：
/usr/...
Getting the object's property name
...DN
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys
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List comprehension: Returning two (or more) items for each item
...bda x: x + 2
>>> g = lambda x: x ** 2
>>> list(chain.from_iterable((f(x), g(x)) for x in range(3)))
[2, 0, 3, 1, 4, 4]
Timings:
from timeit import timeit
f = lambda x: x + 2
g = lambda x: x ** 2
def fg(x):
yield f(x)
yield g(x)
print timeit(stmt='list(chain.from_itera...
Set the value of a variable with the result of a command in a Windows batch file
...%a in ('command1 ^| command2') do set VAR=%%a.
– Bill_Stewart
Mar 4 '16 at 19:23
@Bill_Stewart you just saved my day, ...
Why is printing to stdout so slow? Can it be sped up?
... I experimented earlier with huge (up to 10MB with fp = os.fdopen(sys.__stdout__.fileno(), 'w', 10000000)) python-side buffers. Impact was nil. ie: still long tty delays. This made me think/realize that you just postpone the slow tty problem... when python's buffer finally flushes the tty st...
Finding quaternion representing the rotation from one vector to another
...ion is produced -- check and see for yourself).
// N.B. the arguments are _not_ axis and angle, but rather the
// raw scalar-vector components.
Quaternion(float w, Vector3 xyz);
Quaternion get_rotation_between(Vector3 u, Vector3 v)
{
// It is important that the inputs are of equal length when
...