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How to access the first property of a Javascript object?
...ject.keys return order is not guaranteed as per ECMAScript however unofficially it is by all major browsers implementations, please read https://stackoverflow.com/a/23202095 for details on this.
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Django ManyToMany filter()
...nes__in=[zone1, zone2, zone3])
The double underscore (__) syntax is used all over the place when working with querysets.
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What is meant by 'first class object'?
...nction
literal) if it treats functions as
first-class objects. Specifically,
this means that the language supports
constructing new functions during the
execution of a program, storing them
in data structures, passing them as
arguments to other functions, and
returning them as the va...
How do exceptions work (behind the scenes) in c++
...
Instead of guessing, I decided to actually look at the generated code with a small piece of C++ code and a somewhat old Linux install.
class MyException
{
public:
MyException() { }
~MyException() { }
};
void my_throwing_function(bool throwit)
{
if (...
Like Operator in Entity Framework?
...attern in a specified expression, or zeros if the pattern is not found, on all valid text and character data types
Namespace: System.Data.Objects.SqlClient
Assembly: System.Data.Entity (in System.Data.Entity.dll)
A bit of an explanation also appears in this forum thread.
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Type Checking: typeof, GetType, or is?
...
All are different.
typeof takes a type name (which you specify at compile time).
GetType gets the runtime type of an instance.
is returns true if an instance is in the inheritance tree.
Example
class Animal { }
class Do...
What is “lifting” in Haskell?
...ill now refute me by showing how lifts are a category or something).
Typically you have some data type with a parameter. Something like
data Foo a = Foo { ...stuff here ...}
Suppose you find that a lot of uses of Foo take numeric types (Int, Double etc) and you keep having to write code that un...
Spring MVC: How to perform validation?
...out that: I saw it validates a class. Does the class have to be filled manually with the values from the user input, and then passed to the validator?
...
mongodb: insert if not exists
... has built-in support for this. Pass an extra parameter to your update() call: {upsert:true}. For example:
key = {'key':'value'}
data = {'key2':'value2', 'key3':'value3'};
coll.update(key, data, upsert=True); #In python upsert must be passed as a keyword argument
This replaces your if-find-els...
How to move a file?
...
os.rename(), shutil.move(), or os.replace()
All employ the same syntax:
import os
import shutil
os.rename("path/to/current/file.foo", "path/to/new/destination/for/file.foo")
shutil.move("path/to/current/file.foo", "path/to/new/destination/for/file.foo")
os.replace("p...