compile built-in function can be used to precompile an expression to a code object; this code object can then be passed to eval. This will speed up the repeated executions of the evaluated code. The 3rd parameter to compile needs to be the string 'eval'.
>>> code = compile('a * b + c', '&l...
>>> variables = {'a': 6, 'b': 7}
>>> eval('a * b', globals=variables)
42
As a plus, with this the code cannot accidentally refer to the names defined outside:
>>> eval('variables')
{'a': 6, 'b': 7}
>>> eval('variables', globals=variables)
Traceback (most ...
You can fetch the current properties of the Annotation by using Reflection to fetch the Method or Field or Class which has an Annotation applied to it, and then fetching the desired properties.
@Retention(RetentionPolicy.RUNTIME)
@interface MyAnnotation {
String key() default "foo";...
As the static keyword is used for accessing fields and methods without an instantiated class, it can be used to declare constants for use in other classes. These variables will remain constant across every instantiation of the class. By convention, static variables are always ALL_CAPS and use unders...
Static gives a method or variable storage that is not allocated for each instance of the class. Rather, the static variable is shared among all class members. Incidentally, trying to treat the static variable like a member of the class instance will result in a warning:
public class Apple {
pu...
It is possible to create a QtQuick view directly from C++ and to expose to QML C++ defined properties. In the code below the C++ program creates a QtQuick view and exposes to QML the height and width of the view as properties.
main.cpp
#include <QApplication>
#include <QQmlContext>
#...
The OutputCache directive controls the output caching policies of a web page or a user control.
The basic syntax of OutputCache directive is:
<%@ OutputCache Duration="15" VaryByParam="None" %>
You can also use regular expressions to split a string. For example,
import re
data = re.split(r'\s+', 'James 94 Samantha 417 Scarlett 74')
print( data )
# Output: ['James', '94', 'Samantha', '417', 'Scarlett', '74']
You can get rid of manage.py and use the django-admin command instead. To do so, you will have to manually do what manage.py does:
Add your project path to your PYTHONPATH
Set the DJANGO_SETTINGS_MODULE
export PYTHONPATH="/home/me/path/to/your_project"
export DJANGO_SETTINGS_MODULE...
If you have a vsix file, you can install it by running the file.
Get the vsix file (this is the extension installer)
Run the file.
In the window that opens, confirm the installation.
In Visual studio
go to Tools > Extensions and updates...
In the window that opens go to online
Select Visual Studio Gallery
You can search for an extension on the search box at the upper right corner
Select the extension you want to add
Click on download.
Once download is complete, click...
To add annotations, hints, or exclude some code from being executed JavaScript provides two ways of commenting code lines
Single line Comment //
Everything after the // until the end of the line is excluded from execution.
function elementAt( event ) {
// Gets the element from Event coordinate...
Introduced in Java 8, default methods are a way of specifying an implementation inside an interface. This could be used to avoid the typical "Base" or "Abstract" class by providing a partial implementation of an interface, and restricting the subclasses hierarchy.
Observer patte...
Using Kestrel you can specify port using next approaches:
Defining ASPNETCORE_URLS environment variable.
Windows
SET ASPNETCORE_URLS=https://0.0.0.0:5001
OS X
export ASPNETCORE_URLS=https://0.0.0.0:5001
Via command line passing --server.urls parameter
dotnet run --server.urls=http...
When configuring the built-in logging functionality, a common pattern is to create a logger with the __name__ of the current module:
logger = logging.getLogger(__name__)
This means that the fully-qualified name of the module will appear in the logs, making it easier to see where messages have co...
If you have a string that contains Python literals, such as strings, floats etc, you can use ast.literal_eval to evaluate its value instead of eval. This has the added feature of allowing only certain syntax.
>>> import ast
>>> code = """(1, 2, {'foo': 'bar'})"...
It is not possible to use eval or exec to execute code from untrusted user securely. Even ast.literal_eval is prone to crashes in the parser. It is sometimes possible to guard against malicious code execution, but it doesn't exclude the possibility of outright crashes in the parser or the tokenizer....
