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Questions tagged [instances]

An instance is a specific realization of any object.

516 questions
69
votes
2 answers

Why can't you add attributes to object in python?

(Written in Python shell) >>> o = object() >>> o.test = 1 Traceback (most recent call last): File "", line 1, in o.test = 1 AttributeError: 'object' object has no attribute 'test' >>> class test1: pass >>> t =…
quano
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34
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7 answers

Django model instances primary keys do not reset to 1 after all instances are deleted

I have been working on an offline version of my Django web app and have frequently deleted model instances for a certain ModelX. I have done this from the admin page and have experienced no issues. The model only has two fields: name and order and…
pj2452
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26
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6 answers

On Amazon EC2, will the Spot Instance price ever be higher than the On-Demand Price?

The spot prices are generally much less than the normal on-demand prices for EC2 servers but the prices also vary widely. Does it ever happen that the spot price is higher than an on-demand price? If not, doesn't it make sense to always use spot…
eric
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24
votes
4 answers

JavaScript creating new instance of objects

So I am designing a grade book interface and I have a course defined as: then later I want to create a new instance: var gradingareas = new Array("Homework",…
user1991562
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21
votes
4 answers

Obtaining tags from AWS instances with boto

I'm trying to obtain tags from instances in my AWS account using Python's boto library. While this snippet works correctly bringing all tags: tags = e.get_all_tags() for tag in tags: print tag.name, tag.value (e is an EC2…
rodolk
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18
votes
6 answers

Java - How Can I Check If A Class Is Inheriting From Some Class Or Interface?

I need to check: public static boolean check(Class c, Class d) { if (/* c inherits from d */) return true; else return false; } How can I do that ? And is that possible without c.newInstance() ? The title was wrong at…
Bitterblue
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15
votes
3 answers

SSM send command to EC2 instance Failed

I'm trying to use boto3 to run ssh commands on EC2 instances. I read this guide: http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/troubleshooting-remote-commands.html and I did everything of what they wrote there but I keep get error…
Udi Goldberg
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14
votes
3 answers

Microservices: database and microservice instances

Lets say we have a microservice A and a B. B has its own database. However B has to be horizontally scaled, thus we end up having 3 instances of B. What happens to the database? Does it scale accordingly, does it stays the same (centralized)…
nobitta
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14
votes
1 answer

Object-oriented languages without class concept

I am reading introduction to Scala paper and found following statement: It should be noted that some object-oriented languages do not have the concept of class. Question: Which object-oriented languages do not have class concept and how do they…
tommyk
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14
votes
3 answers

Why doesn't Python call instance method __init__() on instance creation but calls class-provided __init__() instead?

I'm overring the __new__() method of a class to return a class instance which has a specific __init__() set. Python seems to call the class-provided __init__() method instead of the instance-specific method, although the Python documentation…
vkoukis
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13
votes
1 answer

Objective-C: Creating Instance from Class Reference

You can create a class reference with the following code: Class M = [NSMutableString class]; // NSMutableString (for example). You can then call methods on that saved class with code like this: [M string]; But can you create instances, from that…
Alex Coplan
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13
votes
5 answers

Detect number of processes running with the same name

Any ideas of how to write a function that returns the number of instances of a process is running? Perhaps something like this? function numInstances([string]$process) { $i = 0 while() { …
Jack
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13
votes
9 answers

How to Count Number of Instances of a Class

Can anyone tell me how to count the number of instances of a class? Here's my code public class Bicycle { //instance variables public int gear, speed, seatHeight; public String color; //constructor public Bicycle(int gear, int…
RifferRaffers
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11
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2 answers

Python: Create a duplicate of an instance of a class

I have an instance 'graph_main' of a class BipartiteGraph which I've defined. All I need now is to keep this instance untouched but create another instance 'graph1' of this class that is identical to 'graph_main'. But for some reason the graph_main…
mathamateur
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10
votes
2 answers

TypeScript class decorator that modifies object instance

I'm making a plugin for Aurelia and need a class decorator that adds attributes to the new object instance, and calls an external function with the new object as an argument. I've looked through examples, and so far I've put together…
jwx
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