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• Switching from php to python

  - by ts

  Hello I am trying to make a list of things which can be difficult/surprising to someone who is changing language from PHP to Python. so far i have rather short list: forget require / include, learn import (this was most difficult to me - to understand package - module - class - object hierarchy and its mapping to filesystem) you can't just upload file on server to have webpage (-mod_python, wsgi etc) learn the python way for use variable class names (new $class() vs import + getattr) / operator in python 2.x and all float-related horrors those were difficult to me, it takes few days before mind adapts a new paradigm after i found that there is few other areas which could be challenging for someone with (too) many years of php: everything is an object you have to live with exceptions array vs list, set, dictionary, tuple ... learn (effective) list comprehensions learn generators any other ideas / personal experiences ?

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• Google App Engine & Django Sandbox: Shell and Web seem to be using different datastores?

  - by tones

  I'm new to both Django and Google App Engine, and am using a sandbox in OSX10.6 with the GoogleAppEngineLauncher. I've got a basic "bookstore" application running from the tutorial in the OReilly "Programming Google App Engine" book. Here's the bug: If I add a new object to the datastore through the web interface, then it's readable through the web interface, but does not appear to exist if I query the datastore through the shell. Vice versa: If I add an object in the shell, then I can read it from the shell, but it doesn't appear in the web interface. Any thoughts or theories would be welcome. Thanks! =T=

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• A generic list of generics

  - by SnOrfus

  I'm trying to store a list of generic objects in a generic list, but I'm having difficulty declaring it. My object looks like: public class Field<T> { public string Name { get; set; } public string Description { get; set; } public T Value { get; set; } /* ... */ } I'd like to create a list of these. My problem is that each object in the list can have a separate type, so that the populated list could contain something like this: { Field<DateTime>, Field<int>, Field<double>, Field<DateTime> } So how do I declare that? List<Field<?>> (I'd like to stay as typesafe as possible, so I don't want to use an ArrayList).

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• How do i generate random data with RSA?

  - by acidzombie24

  After loading my RSACryptoServiceProvider rsa object i would like to create a key for my AES object. Since i dont need to store the AES key (i only need it to decrypt on my prv side) i figure i dont need to store it and i can generate it with my public key. I thought doing rsa.Encrypt(byte[] with 4 hardcoded bytes); would generate the data i need. It turns out everytime i call this function even with the same data i get different results. So theres no way for me to recreate the AES key if its different everytime. How can i generate data with RSA in a way that i can recreate anytime i need?

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• what is the purpose of numeric/boolean/string objects as opposed to primitive values?

  - by zespri

  In javascript you can call a function as a function or as a constructor. For example you can do : myObject = new Number(13); myPrimitiveValue = Number(13); or simply myPrimitiveValue = 13; I understand the difference between the results. Can you explain me under which reasonable circumstances creating a number, a boolean or a string as an object is desirable? For example, ability to set new properties (this is something you can do on objects but can't really do on primitive values) is almost always a bad idea for objects containing number/boolean/string. Why would I want a numeric/boolean/string object?

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• the way to get a value from a hidden type correctly

  - by kawtousse

  hey, in a html table i construct in each row an edit buttton like the following: retour.append("<input type=\"hidden\" id=\"id_"+nomTab+"_"+compteur+"\" value=\""+object.getIdDailyTimeSheet()+"\" name=\"hd_"+compteur+"\" />"); this is the hidden type then i do the following: retour.append("<button id=edit name=edit type=button onClick= editarow()>"); retour.append("<img src=edit.gif />"); retour.append("</button>"); retour.append("</td>"); here i am using the hidden type to differenciate between my rows with it. Now I am trying to get the parameter called here: value=\""+object.getIdDailyTimeSheet() in my servlet to do an update query based on the IdDailyTimeSheet. I didn't untill know find the way to get this value every time i click the edit button (i do its submit with the javascript). thanks for help.

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• Conceptual data modeling: Is RDF the right tool? Other solutions?

  - by paprika

  I'm planning a system that combines various data sources and lets users do simple queries on these. A part of the system needs to act as an abstraction layer that knows all connected data sources: the user shouldn't [need to] know about the underlying data "providers". A data provider could be anything: a relational DBMS, a bug tracking system, ..., a weather station. They are hooked up to the query system through a common API that defines how to "offer" data. The type of queries a certain data provider understands is given by its "offer" (e.g. I know these entities, I can give you aggregates of type X for relationship Y, ...). My concern right now is the unification of the data: the various data providers need to agree on a common vocabulary (e.g. the name of the entity "customer" could vary across different systems). Thus, defining a high level representation of the entities and their relationships is required. So far I have the following requirements: I need to be able to define objects and their properties/attributes. Further, arbitrary relations between these objects need to be represented: a verb that defines the nature of the relation (e.g. "knows"), the multiplicity (e.g. 1:n) and the direction/navigability of the relation. It occurs to me that RDF is a viable option, but is it "the right tool" for this job? What other solutions/frameworks do exist for semantic data modeling that have a machine readable representation and why are they better suited for this task? I'm grateful for every opinion and pointer to helpful resources.

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• C# determining generic type

  - by Chris Klepeis

  I have several templated objects that all implement the same interface: I.E. MyObject<datatype1> obj1; MyObject<datatype2> obj2; MyObject<datatype3> obj3; I want to store these objects in a List... I think I would do that like this: private List<MyObject<object>> _myList; I then want to create a function that takes 1 parameter, being a datatype, to see if an object using that datatype exists in my list.... sorta clueless how to go about this. In Pseudo code it would be: public bool Exist(DataType T) { return (does _myList contain a MyObject<T>?); }

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• Does a native php (5+) function exist that does the following in 1 line?

  - by Vinh

  function array_value_from_key($array,$key) { return !empty($array[$key]) ? $array[$key] : null; } The reason I ask is because I have a class function that returns an array. Instead of having to do $myArray = myClass::giveMeArray(); $myValue = $myArray[$myKey]; I'd like to do something along the lines of $myValue = array_value_from_key(myClass::giveMeArray(),$myKey); When an object is returned, you can chain the object such as $myValue = myClass::giveMeObject()->aValue; Voila, nice and clean.. not being able to find what seems to be a simple and trivial function is driving me crazy... PS.. one more example of how I'd like to use such a function if(arrayKeyVal(aClass::giveMeArray(),$myKey)) { do_something(); }

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• fields_for to stop pluralizing.

  - by Dmitriy Likhten

  I have a fields_for tag, where I specify the prefix (lets say for some good reasons), and this is supposed to represent a one-to-one relationship. I am trying to represent a relationship widget has_many thingamagigs thingamagig has_one whatchamacallit The field_for code is: fields_for "widgt[thingamagigs_attributes][][whatchamacallit_attributes]", thingamagig.whatchamacallit do |x| which generates names (wrongly): widget[thingamagigs_attributes][][whatchamacallit_attributes][][value] The better solution would be t.fields_for :whatchamacallit do |x| where t = fields_for the thingamagig... However if I do that, the following names are generated widgt[thingamagigs_attributes][whatchamacallit_attributes][] which is completely wrong as all other fields for a thingamagig is... widgt[thingamagigs_attributes][][name] So in all cases I am screwed. The original field_for using a string cannot be used with accepts_nested_attributes_for :whatchamacallit since whatchamacallit is a singular relationship and an object is expected not an array. The second fields_for will simply not work because rails cannot parse the params object correctly. Is there a way to tell the first forms_for to not add the [] after [whatchamacallit_attributes] in all field names?

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• Communication between c++ objects.

  - by Pradyot

  This is an issue, that I have come acrosss earlier. Basically a c++ object has a member object that does some work, once the work is done , a notification needs to made to the parent. What is the most elegant solution to allow this communication. Does being in this position indicate a flaw with the design to begin with? To elaborate. class A { B member; void do_something(); } class B{ void talk_to_network(); }; void do_something() { //Conditional wait on a variable that will change when talk to network completes. //So need a way for B to inform A, that it is done. }

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• Setting the size of a silverlight window at runtime automatically?

  - by dilbert789

  I need to be able to change the size of my Silverlight object at run time because I have content that changes in size dramatically between pages, and I'd rather not show a Silverlight scroll bar inside the browser scroll bar. I was able to do the following to get it to work: In the aspx page hosting the silverlight control: - Set your Div to the starting size you need it to be - Set the Silverlight Obejct to width=”100%” height=”100%” In your Main page add this: public static void ChangeSize(string height) { var myDiv = HtmlPage.Plugin.Parent; while (myDiv.TagName != "div") myDiv = myDiv.Parent; myDiv.SetStyleAttribute("height", height); } Anywhere you want to now change the size of the page do this: string newHeight = (App.Current.Host.Content.ActualHeight + 75).ToString(); MainPage.ChangeSize(newHeight + "px"); //App.Current.Host.Content.ActualHeight will get the current actual height of the object Is there a way that I can set this to re-size automatically so that I do not have to specify the amount to change? Currently using SL 2, interested in if there is another way in a different version though.

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• Grid View selected index

  - by user2924573

  I have a grid which contains a edit button . When i click the edit button and debug it does not hit to the selected index change event . There are no build errors code behind the grid public void btnModemDetailsEdit_Click(object sender, EventArgs e) { isEdit = true; } protected void gridModemDetails_SelectedIndexChanged(object sender, EventArgs e) { int id = Convert.ToInt32(GridModemDetails.DataKeys[GridModemDetails.SelectedIndex].Values["gridModemDetails_SelectedIndexChanged"].ToString()); } <asp:GridView ID="GridModemDetails" runat="server" Width="435px" DataKeyNames="ModemId" AllowPaging="True" OnSelectedIndexChanged="gridModemDetails_SelectedIndexChanged" AutoGenerateColumns="False"> <Columns> <asp:TemplateField HeaderText="Edit" Visible="True" > <ItemTemplate> <asp:LinkButton ID="btnModemDetailsEdit" AccessibleHeaderText="Edit" ButtonType="Button" Text="Edit" HeaderText="Edit" runat="server" OnClick="btnModemDetailsEdit_Click" runat="server"/> </ItemTemplate> </asp:TemplateField>

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• JPA Bidirectional OneToMany and ManyToOne?

  - by PhoenixJon

  I'm using Oracle JDeveloper 11g Release 2. I created two tables A and B using SQL developer. Table A has a FK to table B. Using the Entities from Tables function, I created two JPA files from it. A has @ManyToOne annotation on FK. And also B has @OneToMany annotation to A. I don't want this. Can I remove this @OneToMany annotation automatically? public class A implements Serializable { ... @ManyToOne @JoinColumn(name = "FIELD_B") private B b; ... } public class B implements Serializable { ... @OneToMany(mappedBy = "B") private List<A> assetList; ... } I don't need @OneToMany mapping.

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• Why javabeans framework create the IndexedPropertyDescriptor for the NON index method

  - by George Macus

  I'm not familiar with java beans framework, in the below scenario, I got the IndexedPropertyDescriptor for the method getFooWithX, could someone explain why? public class IntrospectorTest { public static void main(String[] args) throws IntrospectionException { BeanInfo info = Introspector.getBeanInfo(SubClass.class); PropertyDescriptor[] descriptors = info.getPropertyDescriptors(); for (int i = 0; i < descriptors.length; i++) { System.out.println(descriptors[i].getClass().getName() + ":" + descriptors[i].getName()); } } } abstract class BaseClass { public abstract Object getFoo(); } abstract class SubClass extends BaseClass { public Object getFooWithX(int x) { return null; } } and the result will be: java.beans.PropertyDescriptor:class java.beans.PropertyDescriptor:foo java.beans.IndexedPropertyDescriptor:fooWithX Why?

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• How to map one class against multiple tables with SQLAlchemy?

  - by tote

  Lets say that I have a database structure with three tables that look like this: items - item_id - item_handle attributes - attribute_id - attribute_name item_attributes - item_attribute_id - item_id - attribute_id - attribute_value I would like to be able to do this in SQLAlchemy: item = Item('item1') item.foo = 'bar' session.add(item) session.commit() item1 = session.query(Item).filter_by(handle='item1').one() print item1.foo # => 'bar' I'm new to SQLAlchemy and I found this in the documentation (http://www.sqlalchemy.org/docs/05/mappers.html#mapping-a-class-against-multiple-tables): j = join(items, item_attributes, items.c.item_id == item_attributes.c.item_id). \ join(attributes, item_attributes.c.attribute_id == attributes.c.attribute_id) mapper(Item, j, properties={ 'item_id': [items.c.item_id, item_attributes.c.item_id], 'attribute_id': [item_attributes.c.attribute_id, attributes.c.attribute_id], }) It only adds item_id and attribute_id to Item and its not possible to add attributes to Item object. Is what I'm trying to achieve possible with SQLAlchemy? Is there a better way to structure the database to get the same behaviour of "dynamic columns"?

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• Selecting dictionary items by key efficiently in Python

  - by user248237

  suppose I have a dictionary whose keys are strings. How can I efficiently make a new dictionary from that which contains only the keys present in some list? for example: # a dictionary mapping strings to stuff mydict = {'quux': ..., 'bar': ..., 'foo': ...} # list of keys to be selected from mydict keys_to_select = ['foo', 'bar', ...] The way I came up with is: filtered_mydict = [mydict[k] for k in mydict.keys() \ if k in keys_to_select] but I think this is highly inefficient because: (1) it requires enumerating the keys with keys(), (2) it requires looking up k in keys_to_select each time. at least one of these can be avoided, I would think. any ideas? I can use scipy/numpy too if needed.

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• Designing operation (a,b) -> (c,d)

  - by golergka

  I have an operation that I need to design. That operation takes two objects of a certain class X, and returns two new objects of the same class (I may need the originals later). The logic that dictates the selection of this object is contained in class Y. On one hand, I don't want class Y to know details about class X implementation; on the other, I don't want class X to know details about selecting the different objects to perform this operation on. If that was all the problem, I'd just create a static method on class A. However, the methods in language I'm working on return only one object. Also, the operation needs to be robust, and calling operation two times to get C and D respectively isn't possible, as both C & D both rely on a single random number. How should I design such operation? Update: I'm using Obejctive C.

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• Java synchronizing static list ?

  - by JavaUser

  Hi, In a Java class , i am having a static list so this list is shared across all the objects of this class.The business logic in this class will run periodically which is invoked by some method with out passing instance parameters.Now I want to invoke this run method based on the list(I will add some vales into this list based on JMS) ,this list may empty sometimes and after finishing the run , i am emptying this list.Now my question is , whether I need to synchronize this list or not? Also let me know is there any other way to pass value in one object instance(Thread1) to other object instance (Thread2) other than having Static variable(static list)? Thx

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• Set a tab page on lload event of a form

  - by tanu

  i have a form with many tabs on it. I want to set a specific tab page to show on load of the form everytime i load the form I used TabPageControl1.SelectedTab=MyTabPage; but the value of selectedtab is null. It is throwing an exception that reference not set to an object. private void PreferencesForm_Load(object sender, EventArgs e) { this.cbxCustomDataType.DrawMode = DrawMode.OwnerDrawFixed; this.cbxCustomDataType.DrawItem += new DrawItemEventHandler(cbxCustomDataType_DrawItem); this.cbxColumnDataType.DrawMode = DrawMode.OwnerDrawFixed; this.cbxColumnDataType.DrawItem += new DrawItemEventHandler(cbxColumnDataType_DrawItem); GetProjectDetails(); this.preferencesTabControl.SelectedTab= tpCompareUpdate; }

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• How can i add column name in list generic?

  - by Phsika

  class MyExcelSheets { public List MyColumnNames { get; set; } } how can i add Excel data's column name in "List MyColumnNames ". it returns to me Object reference not set to an instance of an object. i want to use above class in: myexcelSheet = new MyExcelSheets(); myexcelSheet.MyColumnNames = new MyExcelSheets().MyColumnNames; foreach (DataColumn col in dTable.Columns) myexcelSheet.MyColumnNames.Add(col.ColumnName.ToString()); How can i solve it? Error: NullReferenceException

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• Noob question: Draw a quad parallel to the view.

  - by Jack

  Hi all, ok what I want to do is to draw a quad in the scene that lays on a plane parallel to the view. So it should appear flat. More in particular, I think I didn't get very well how the mechanism of gluLookAt works in comparison with the functions glTranslate and glRotate: If I position the view "manually" using the functions glTranslate and glRotate whenever I draw an object its position is relative to the current view. And I understand that this is due to the transformation matrix in the stack. However when I use the gluLookAt that should automatically set the view, the coordinates of the object I want to draw must be "absolute" to show it properly. Thanks in advance.

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• AS3: How to get all XML-Nodes with a special attribute? (With sourch)

  - by insnet

  Hi there The Challenge: i d like to collect all nodes with the attribute "id". The Problem: The code doenst work with nested nodes. <?xml version="1.0" encoding="utf-8"?><contentmap><fonts id="fonts"> fonts/Arial.swf swf/library_main.swf private function onXMLLoader(event : Event) : void { _xml = _loader.getXML(event.target.url.url); var searchTerms : XMLList = _xml.*.(hasOwnProperty('@id')); if (searchTerms.length() 0 ) { _NodeArray = new Array(); _parseNode(searchTerms); } private function _parseNode(xml : XMLList) : void { for each (var node: XML in xml) { if(!node.hasSimpleContent()) { _parseNode(node.children()); } else { var nodeObject : Object = new Object(); nodeObject['value'] = node.text(); for each(var a:XML in node.@*) { var name : String = String(a.name()); nodeObject[name] = a.toXMLString(); } _NodeArray.push(nodeObject); } } }

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• DAQ Triggers in Matlab

  - by RidePlanet

  I'm writing a program that detects the speed of a object by hall effect sensors that are run into MATLAB through a DAQ (MCC USB-1408FS) The problem that has arisen is that I'm using a non-stop scan technique to detect the state of one of 3 sensors. Unfortunately this means that unless the object is rotating past each sensor at the exact rate the program runs, I will see an instantaneous speed (done by comparing the time between two sensors) of zero. I need the sensors to signal the program to count when they are hit, instead of constantly scanning for the signal. How can this be done?

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• Convert sets to frozensets as values of a dictionary

  - by Space_C0wb0y

  I have dictionary that is built as part of the initialization of my object. I know that it will not change during the lifetime of the object. The dictionary maps keys to sets. I want to convert all the values from sets to frozensets, to make sure they do not get changed. Currently I do that like this: for key in self.my_dict.iterkeys(): self.my_dict[key] = frozenset(self.my_dict[key]) Is there a simpler way to achieve this? I cannot build frozenset right away, because I do not how much items will be in each set until i have built the complete dictionary.

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