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...
The Application directive defines application-specific attributes. It is provided at the top of the global.aspx file.
The basic syntax of Application directive is:
<%@ Application Language="C#" %>
The attributes of the Application directive are:
AttributesDescriptionInheritsThe...
The control directive is used with the user controls and appears in the user control (.ascx) files.
The basic syntax of Control directive is:
<%@ Control Language="C#" EnableViewState="false" %>
The attributes of the Control directive are:
AttributesDescriptionAutoEv...
The Implement directive indicates that the web page, master page or user control page must implement the specified .Net framework interface.
The basic syntax for implements directive is:
<%@ Implements Interface="interface_name" %>
This example show how you can check if a service already exists (i.e., is installed on the machine) or not. This code requires only the lowest privileges necessary, so each process can perform the check, no matter what level of security it is running at.
#define UNICODE
#define _UNICODE
#include ...
>>> '{0:.0f}'.format(42.12345)
'42'
>>> '{0:.1f}'.format(42.12345)
'42.1'
>>> '{0:.3f}'.format(42.12345)
'42.123'
>>> '{0:.5f}'.format(42.12345)
'42.12345'
>>> '{0:.7f}'.format(42.12345)
'42.1234500'
Same hold for other way of referenc...
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']
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...
int x = INT_MAX + 1;
// x can be anything -> Undefined behavior
If during the evaluation of an expression, the result is not mathematically defined or not in the range of representable values for its type, the behavior is undefined.
(C++11 Standard paragraph 5/4)
This is one of the mo...
By default, Django renders ForeignKey fields as a <select> input. This can cause pages to be load really slowly if you have thousands or tens of thousand entries in the referenced table. And even if you have only hundreds of entries, it is quite uncomfortable to look for a particular entry amo...
Using threading & queue:
from socket import socket, AF_INET, SOCK_STREAM
from threading import Thread
from queue import Queue
def echo_server(addr, nworkers):
print('Echo server running at', addr)
# Launch the client workers
q = Queue()
for n in range(nworkers):
...
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...
In a non-strict-mode scope, when a variable is assigned without being initialized with the var, const or the let keyword, it is automatically declared in the global scope:
a = 12;
console.log(a); // 12
In strict mode however, any access to an undeclared variable will throw a reference error:
&...
Differences in subsetting syntax
A data.table is one of several two-dimensional data structures available in R, besides data.frame, matrix and (2D) array. All of these classes use a very similar but not identical syntax for subsetting, the A[rows, cols] schema.
Consider the following data stored i...
Delegates may have variant type parameters.
delegate void Action<in T>(T t); // T is an input
delegate T Func<out T>(); // T is an output
delegate T2 Func<in T1, out T2>(); // T1 is an input, T2 is an output
This follows from the Liskov Substitution Principle, w...
