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How to test if list element exists?
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This is actually a bit trickier than you'd think. Since a list can actually (with some effort) contain NULL elements, it might not be enough to check is.null(foo$a). A more stringent test might be to check that the name is actually defin...
String comparison in Python: is vs. == [duplicate]
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For all built-in Python objects (like
strings, lists, dicts, functions,
etc.), if x is y, then x==y is also
True.
Not always. NaN is a counterexample. But usually, identity (is) implies equality (==). The converse is n...
AWS S3 copy files and folders between two buckets
...rows the following error A client error (PermanentRedirect) occurred when calling the ListObjects operation: The bucket you are attempting to access must be addressed using the specified endpoint. Please send all future requests to this endpoint.
– Giovanni Bitliner
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What does the Reflect object do in JavaScript?
...ble:
ES6 spec, Reflection
MDN Reflect (including details and examples to all of its methods)
Original answer (for (historic) understanding and extra examples):
The Reflection proposal seems to have progressed to the Draft ECMAScript 6 Specification. This document currently outlines the Reflect...
Test if a variable is a list or tuple
... excludes custom sequences, iterators, and other things that you might actually need. However, sometimes you need to behave differently if someone, for instance, passes a string. My preference there would be to explicitly check for str or unicode like so:
import types
isinstance(var, types.String...
Test PHP headers with PHPUnit
...78
Error: Class 'PHPUnit_Util_Configuration' not found in - on line 378
Call Stack:
0.0013 582512 1. {main}() -:0
Try add this to your bootstrap file to fix it:
<?php
if (!defined('PHPUNIT_COMPOSER_INSTALL')) {
define('PHPUNIT_COMPOSER_INSTALL', __DIR__ . '/path/to/composer/ven...
How do I get a PHP class constructor to call its parent's parent's constructor?
I need to have a class constructor in PHP call its parent's parent's (grandparent?) constructor without calling the parent constructor.
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If Python is interpreted, what are .pyc files?
...'translated'. Python is then compiled to a bytecode. AFAIK, only Bash is really interpreted , all other popular "interpreted" languages are all compiled to a bytecode.
– bfontaine
Aug 6 '14 at 13:42
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Hidden Features of Java
...en I first discovered it, never heard of it before.
ThreadLocals are typically not so widely known as a way to store per-thread state.
Since JDK 1.5 Java has had extremely well implemented and robust concurrency tools beyond just locks, they live in java.util.concurrent and a specifically interest...
How is pattern matching in Scala implemented at the bytecode level?
...atterns like or patterns and combinations like "case Foo(45, x)", but generally those are just logical extensions of what I just described. Patterns can also have guards, which are additional constraints on the predicates. There are also cases where the compiler can optimize pattern matching, e.g...