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  • Getting an Error Trying to Create an Object in Python

    - by Nick Rogers
    I am trying to create an object from a class in python but I am getting an Error, "e_tank = EnemyTank() TypeError: 'Group' object is not callable" I am not sure what this means, I have tried Google but I couldn't get a clear answer on what is causing this error. Does anyone understand why I am unable to create an object from my EnemyTank Class? Here is my code: #Image Variables bg = 'bg.jpg' bunk = 'bunker.png' enemytank = 'enemy-tank.png' #Import Pygame Modules import pygame, sys from pygame.locals import * #Initializing the Screen pygame.init() screen = pygame.display.set_mode((640,360), 0, 32) background = pygame.image.load(bg).convert() bunker_x, bunker_y = (160,0) class EnemyTank(pygame.sprite.Sprite): e_tank = pygame.image.load(enemytank).convert_alpha() def __init__(self, startpos): pygame.sprite.Sprite.__init__(self, self.groups) self.pos = startpos self.image = EnemyTank.image self.rect = self.image.get_rect() def update(self): self.rect.center = self.pos class Bunker(pygame.sprite.Sprite): bunker = pygame.image.load(bunk).convert_alpha() def __init__(self, startpos): pygame.spriter.Sprite.__init__(self, self.groups) self.pos = startpos self.image = Bunker.image self.rect = self.image.get_rect() def getCollisionObjects(self, EnemyTank): if (EnemyTank not in self._allgroup, False): return False self._allgroup.remove(EnemyTank) result = pygame.sprite.spritecollide(EnemyTank, self._allgroup, False) self._allgroup.add(EnemyTank) def update(self): self.rect.center = self.pos #Setting Up The Animation x = 0 clock = pygame.time.Clock() speed = 250 allgroup = pygame.sprite.Group() EnemyTank = allgroup Bunker = allgroup e_tank = EnemyTank() bunker = Bunker()5 #Main Loop while True: for event in pygame.event.get(): if event.type == QUIT: pygame.quit() sys.exit() screen.blit(background, (0,0)) screen.blit(bunker, (bunker_x, bunker_y)) screen.blit(e_tank, (x, 0)) pygame.display.flip() #Animation milli = clock.tick() seconds = milli/1000. dm = seconds*speed x += dm if x>640: x=0 #Update the Screen pygame.display.update()

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  • Python beginner having trouble running code

    - by Protean
    For some reason this code will not seem to run in the interpreter. When I hit F5 nothing happens, not even the debugger seems to recognize it. I assume it has something to do with the class, as when removed the interpreter seems to recognize the rest of the code. Please tell me what I am doing wrong. Edit: I have restarted the interpreter multiple times, any other piece of code I try to load runs fine, just this one is having trouble. print ('Why won't this work?') class sorting_class: def __init__(self): self.order = ['a', 'b', 'c', 'd'] self.globali = 0 self.orderi = 0 self.sortedlist = [] def sort(self, array): carry, leave = [] for arrayi in array: print ('run', arrayi) if self.order[self.orderi] == arrayi[self.globali]: carry.append(arrayi) else: if self.globali != 0: leave.append(arrayi) return carry, leave def srt(self, array): globalii = 0 carry, leave = my.sort(array) while len(self.sortedlist) != len(array): if len(self.carry) == 1: self.sortedlist.append(carry) arrayt = leave self.globali = 1 self.orderi = 0 carry, leave = my.sort(arrayt) elif len(self.carry) == 0: if len(self.leave) != 0: arrayt = leave self.globali = 1 self.orderi += 1 my.sort(arrayt) else: self.arrayt globalii += 1 self.orderi = globalii self.globali = 0 my.sort(arrayt) self.orderi = 0 else: arrayt = carry carry = [] self.globali += 1 carry, leave += my.sort(arrayt) my = sorting_class() x = ['ac', 'bc' ,'ab', 'da'] my.srt(x)

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  • python __getattr__ help

    - by Stefanos Tux Zacharakis
    Reading a Book, i came across this code... # module person.py class Person: def __init__(self, name, job=None, pay=0): self.name = name self.job = job self.pay = pay def lastName(self): return self.name.split()[-1] def giveRaise(self, percent): self.pay = int(self.pay *(1 + percent)) def __str__(self): return "[Person: %s, %s]" % (self.name,self.pay) class Manager(): def __init__(self, name, pay): self.person = Person(name, "mgr", pay) def giveRaise(self, percent, bonus=.10): self.person.giveRaise(percent + bonus) def __getattr__(self, attr): return getattr(self.person, attr) def __str__(self): return str(self.person) It does what I want it to do, but i do not understand the __getattr__ function in the Manager class. I know that it Delegates all other attributes from Person class. but I do not understand the way it works. for example why from Person class? as I do not explicitly tell it to. person(module is different than Person(class) Any help is highly appreciated :)

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  • How to make safe cast using generics in C#?

    - by TN
    I want to implement a generic method on a generic class which would allow to cast safely, see example: public class Foo<T> : IEnumerable<T> { ... public IEnumerable<R> SafeCast<R>() where T : R { return this.Select(item => (R)item); } } However, the compiler tells me that Foo<T>.SafeCast<R>() does not define parameter 'T'. I understand this message that I cannot specify a constraint on T in the method since it is not defined in the method. But how can I specify an inverse constraint?

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  • Getting exception when trying to monkey patch pymongo.connection._Pool

    - by Creotiv
    I use pymongo 1.9 on Ubuntu 10.10 with python 2.6.6 When i trying to monkey patch pymongo.connection._Pool i'm getting error on connection: AutoReconnect: could not find master/primary But when i change _Pool class in pymongo.connection module, it work pretty fine. Even if i copy _Pool implementation from pymongo.connection module and will try to monkey patch by the same code, it still giving same exception. I need to remove threading.local from _Pool class, because i use gevent and i need to implement Pool for all mongo connections(for all threads). I use this code: import pymongo class GPool: """A simple connection pool. Uses thread-local socket per thread. By calling return_socket() a thread can return a socket to the pool. Right now the pool size is capped at 10 sockets - we can expose this as a parameter later, if needed. """ # Non thread-locals __slots__ = ["sockets", "socket_factory", "pool_size","sock"] #sock = None def __init__(self, socket_factory): self.pool_size = 10 if not hasattr(self,"sock"): self.sock = None self.socket_factory = socket_factory if not hasattr(self, "sockets"): self.sockets = [] def socket(self): # we store the pid here to avoid issues with fork / # multiprocessing - see # test.test_connection:TestConnection.test_fork for an example # of what could go wrong otherwise pid = os.getpid() if self.sock is not None and self.sock[0] == pid: return self.sock[1] try: self.sock = (pid, self.sockets.pop()) except IndexError: self.sock = (pid, self.socket_factory()) return self.sock[1] def return_socket(self): if self.sock is not None and self.sock[0] == os.getpid(): # There's a race condition here, but we deliberately # ignore it. It means that if the pool_size is 10 we # might actually keep slightly more than that. if len(self.sockets) < self.pool_size: self.sockets.append(self.sock[1]) else: self.sock[1].close() self.sock = None pymongo.connection._Pool = GPool

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  • How to convert a gi-normous integer (in string format) to hex format? (C#)

    - by eviljack
    Given a potentially huge integer value (in c# string format), I want to be able to generate it's hex equivalent. Normal methods don't apply here as we are talking arbitrarily large numbers, 50 digits or more. The techniques I've seen which use a technique like this: // Store integer 182 int decValue = 182; // Convert integer 182 as a hex in a string variable string hexValue = decValue.ToString("X"); // Convert the hex string back to the number int decAgain = int.Parse(hexValue, System.Globalization.NumberStyles.HexNumber); won't work because the integer to convert is too large. For example I need to be able to convert a string like this: 843370923007003347112437570992242323 to it's hex equivalent. these don't work: http://stackoverflow.com/questions/1139957/c-convert-int-to-hex-and-back-again http://stackoverflow.com/questions/74148/how-to-convert-numbers-between-hex-and-decimal-in-c

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  • FIFO dequeueing in python?

    - by Aaron Ramsey
    hello again everybody— I'm looking to make a functional (not necessarily optimally efficient, as I'm very new to programming) FIFO queue, and am having trouble with my dequeueing. My code looks like this: class QueueNode: def __init__(self, data): self.data = data self.next = None def __str__(self): return str(self.data) class Queue: def__init__(self): self.front = None self.rear = None self.size = 0 def enqueue(self, item) newnode = QueueNode(item) newnode.next = None if self.size == 0: self.front = self.rear = newnode else: self.rear = newnode self.rear.next = newnode.next self.size = self.size+1 def dequeue(self) dequeued = self.front.data del self.front self.size = self.size-1 if self.size == 0: self.rear = None print self.front #for testing if I do this, and dequeue an item, I get the error "AttributeError: Queue instance has no attribute 'front'." I guess my function doesn't properly assign the new front of the queue? I'm not sure how to fix it though. I don't really want to start from scratch, so if there's a tweak to my code that would work, I'd prefer that—I'm not trying to minimize runtime so much as just get a feel for classes and things of that nature. Thanks in advance for any help, you guys are the best.

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  • Python beginer having trouble running code

    - by Protean
    For some reason this code will not seem to run in the interpreter. When I hit F5 nothing happens, not even the debugger seems to recognize it. I assume it has something to do with the class, as when removed the interpreter seems to recognize the rest of the code. Please tell me what I am doing wrong. Edit: I have restarted the interpreter multiple times, any other piece of code I try to load runs fine, just this one is having trouble. print ('Why won't this work?') class sorting_class: def __init__(self): self.order = ['a', 'b', 'c', 'd'] self.globali = 0 self.orderi = 0 self.sortedlist = [] def sort(self, array): carry, leave = [] for arrayi in array: print ('run', arrayi) if self.order[self.orderi] == arrayi[self.globali]: carry.append(arrayi) else: if self.globali != 0: leave.append(arrayi) return carry, leave def srt(self, array): globalii = 0 carry, leave = my.sort(array) while len(self.sortedlist) != len(array): if len(self.carry) == 1: self.sortedlist.append(carry) arrayt = leave self.globali = 1 self.orderi = 0 carry, leave = my.sort(arrayt) elif len(self.carry) == 0: if len(self.leave) != 0: arrayt = leave self.globali = 1 self.orderi += 1 my.sort(arrayt) else: self.arrayt globalii += 1 self.orderi = globalii self.globali = 0 my.sort(arrayt) self.orderi = 0 else: arrayt = carry carry = [] self.globali += 1 carry, leave += my.sort(arrayt) my = sorting_class() x = ['ac', 'bc' ,'ab', 'da'] my.srt(x)

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  • SQLAlchemy unsupported type error - and table design issues?

    - by Az
    Hi there, back again with some more SQLAlchemy shenanigans. Let me step through this. My table is now set up as so: engine = create_engine('sqlite:///:memory:', echo=False) metadata = MetaData() students_table = Table('studs', metadata, Column('sid', Integer, primary_key=True), Column('name', String), Column('preferences', Integer), Column('allocated_rank', Integer), Column('allocated_project', Integer) ) metadata.create_all(engine) mapper(Student, students_table) Fairly simple, and for the most part I've been enjoying the ability to query almost any bit of information I want provided I avoid the error cases below. The class it is mapped from is: class Student(object): def __init__(self, sid, name): self.sid = sid self.name = name self.preferences = collections.defaultdict(set) self.allocated_project = None self.allocated_rank = 0 def __repr__(self): return str(self) def __str__(self): return "%s %s" %(self.sid, self.name) Explanation: preferences is basically a set of all the projects the student would prefer to be assigned. When the allocation algorithm kicks in, a student's allocated_project emerges from this preference set. Now if I try to do this: for student in students.itervalues(): session.add(student) session.commit() It throws two errors, one for the allocated_project column (seen below) and a similar error for the preferences column: sqlalchemy.exc.InterfaceError: (InterfaceError) Error binding parameter 4 - probably unsupported type. u'INSERT INTO studs (sid, name, allocated_rank, allocated_project) VALUES (?, ?, ?, ?, ?, ?, ?)' [1101, 'Muffett,M.', 1, 888 Human-spider relationships (Supervisor id: 123)] If I go back into my code I find that, when I'm copying the preferences from the given text files, it actually refers to the Project class which is mapped to a dictionary, using the unique project id's (pid) as keys. Thus, as I iterate through each student via their rank and to the preferences set, it adds not a project id, but the reference to the project id from the projects dictionary. students[sid].preferences[int(rank)].add(projects[int(pid)]) Now this is very useful to me since I can find out all I want to about a student's preferred projects without having to run another check to pull up information about the project id. The form you see in the error has the object print information passed as: return "%s %s (Supervisor id: %s)" %(self.proj_id, self.proj_name, self.proj_sup) My questions are: I'm trying to store an object in a database field aren't I? Would the correct way then, be copying the project information (project id, name, etc) into its own table, referenced by the unique project id? That way I can just have the project id field for one of the student tables just be an integer id and when I need more information, just join the tables? So and so forth for other tables? If the above makes sense, then how does one maintain the relationship with a column of information in one table which is a key index on another table? Does this boil down into a database design problem? Are there any other elegant ways of accomplishing this? Apologies if this is a very long-winded question. It's rather crucial for me to solve this, so I've tried to explain as much as I can, whilst attempting to show that I'm trying (key word here sadly) to understand what could be going wrong.

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  • Why does my buffered GraphicsContext application have a flickering problem?

    - by Bibendum
    import wx class MainFrame(wx.Frame): def __init__(self,parent,title): wx.Frame.__init__(self, parent, title=title, size=(640,480)) self.mainPanel=DoubleBufferTest(self,-1) self.Show(True) class DoubleBufferTest(wx.Panel): def __init__(self,parent=None,id=-1): wx.Panel.__init__(self,parent,id,style=wx.FULL_REPAINT_ON_RESIZE) self.SetBackgroundColour("#FFFFFF") self.timer = wx.Timer(self) self.timer.Start(100) self.Bind(wx.EVT_TIMER, self.update, self.timer) self.Bind(wx.EVT_PAINT,self.onPaint) def onPaint(self,event): event.Skip() dc = wx.MemoryDC() dc.SelectObject(wx.EmptyBitmap(640, 480)) gc = wx.GraphicsContext.Create(dc) gc.PushState() gc.SetBrush(wx.Brush("#CFCFCF")) bgRect=gc.CreatePath() bgRect.AddRectangle(0,0,640,480) gc.FillPath(bgRect) gc.PopState() dc2=wx.PaintDC(self) dc2.Blit(0,0,640,480,dc,0,0) def update(self,event): self.Refresh() app = wx.App(False) f=MainFrame(None,"Test") app.MainLoop() I've come up with this code to draw double buffered GraphicsContext content onto a panel, but there's a constant flickering across the window. I've tried different kinds of paths, like lines and curves but it's still there and I don't know what's causing it.

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  • Download office document without the web server trying to render it

    - by Dan Revell
    I'm trying to download an InfoPath template that's hosted on SharePoint. If I hit the url in internet explorer it asks me where to save it and I get the correct file on my disk. If I try to do this programmatically with WebClient or HttpWebRequest then I get HTML back instead. How can I make my request so that the web server returns the actual xsn file and doesn't try to render it in html. If internet explorer can do this then it's logical to think that I can too. I've tried setting the Accept property of the request to application/x-microsoft-InfoPathFormTemplate but that hasn't helped. It was a shot in the dark.

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  • How to repeatedly show a Dialog with PyGTK / Gtkbuilder?

    - by Julian
    I have created a PyGTK application that shows a Dialog when the user presses a button. The dialog is loaded in my __init__ method with: builder = gtk.Builder() builder.add_from_file("filename") builder.connect_signals(self) self.myDialog = builder.get_object("dialog_name") In the event handler, the dialog is shown with the command self.myDialog.run(), but this only works once, because after run() the dialog is automatically destroyed. If I click the button a second time, the application crashes. I read that there is a way to use show() instead of run() where the dialog is not destroyed, but I feel like this is not the right way for me because I would like the dialog to behave modally and to return control to the code only after the user has closed it. Is there a simple way to repeatedly show a dialog using the run() method using gtkbuilder? I tried reloading the whole dialog using the gtkbuilder, but that did not really seem to work, the dialog was missing all child elements (and I would prefer to have to use the builder only once, at the beginning of the program). [SOLUTION] As pointed out by the answer below, using hide() does the trick. But one has to take care that the dialog is in fact destroyed if one does not catch its "delete-event". A simple example that works is: import pygtk import gtk class DialogTest: def rundialog(self, widget, data=None): self.dia.show_all() result = self.dia.run() def destroy(self, widget, data=None): gtk.main_quit() def closedialog(self, widget, data=None): self.dia.hide() return True def __init__(self): self.window = gtk.Window(gtk.WINDOW_TOPLEVEL) self.window.connect("destroy", self.destroy) self.dia = gtk.Dialog('TEST DIALOG', self.window, gtk.DIALOG_MODAL | gtk.DIALOG_DESTROY_WITH_PARENT) self.dia.vbox.pack_start(gtk.Label('This is just a Test')) self.dia.connect("delete-event", self.closedialog) self.button = gtk.Button("Run Dialog") self.button.connect("clicked", self.rundialog, None) self.window.add(self.button) self.button.show() self.window.show() if __name__ == "__main__": testApp = DialogTest() gtk.main()

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  • Which class should store the lookup table?

    - by max
    The world contains agents at different locations, with only a single agent at any location. Each agent knows where he's at, but I also need to quickly check if there's an agent at a given location. Hence, I also maintain a map from locations to agents. I have a problem deciding where this map belongs to: class World, class Agent (as a class attribute) or elsewhere. In the following I put the lookup table, agent_locations, in class World. But now agents have to call world.update_agent_location every time they move. This is very annoying; what if I decide later to track other things about the agents, apart from their locations - would I need to add calls back to the world object all across the Agent code? class World: def __init__(self, n_agents): # ... self.agents = {} self.agent_locations = {} for id in range(n_agents): x, y = self.find_location() agent = Agent(self,x,y) self.agents.append(agent) self.agent_locations[x,y] = agent def update_agent_location(self, agent, x, y): del self.agent_locations[agent.x, agent.y] self.agent_locations[x, y] = agent def update(self): # next step in the simulation for agent in self.agents: agent.update() # next step for this agent # ... class Agent: def __init__(self, world, x, y): self.world = world self.x, self.y = x, y def move(self, x1, y1): self.world.update_agent_location(self, x1, y1) self.x, self.y = x1, y1 def update(): # find a good location that is not occupied and move there for x, y in self.valid_locations(): if not self.location_is_good(x, y): continue if self.world.agent_locations[x, y]: # location occupied continue self.move(x, y) I can instead put agent_locations in class Agent as a class attribute. But that only works when I have a single World object. If I later decide to instantiate multiple World objects, the lookup tables would need to be world-specific. I am sure there's a better solution... EDIT: I added a few lines to the code to show how agent_locations is used. Note that it's only used from inside Agent objects, but I don't know if that would remain the case forever.

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  • Will there ever be a version of Java which does not perform Type Erasure

    - by user63904
    Type erasure enables Java applications that use generics to maintain binary compatibility with Java libraries and applications that were created before generics Generics were introduced in Java 1.5, so presumably the statement "applications that were created before generics" is referring to Java 1.4? Given that Java 1.4 entered its End Of Life around 2006 and was officially End Of Life'd around 2008. Why is type erasure still being performed in Java 7, etc... Has the statement now become self referential i.e. Type erasure enables Java applications that use generics to maintain binary compatibility with Java libraries and applications that were created with Java versions that perform Type Erasure. Meaning therefore that there will never be a version of Java that doesn't perform Type Erasure.

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  • Problem inserting Pygames on a wxPython panel using Boa Constructor

    - by Kohwalter
    Hello, im new in Python so im hoping to to get some help to figure out what is going wrong. Im trying to run a Pygames from within wxPython panel (made on Boa Constructor). To do that i followed the instructions on the http://wiki.wxpython.org/IntegratingPyGame but still it isn't working. Here is the Panel code that was used to make the integration: class PG_panel(wx.Panel): def __init__(self, ID, name, parent, mypos, mysize): # pygame is imported in this class # make it globally available global pygame #self.Fit() wx.Panel.__init__(self, id=wxID_FRMMAINPANELTABULEIRO, name='panelTabuleiro', parent=self, pos=(16, 96), size=mysize) # pygame uses SDL, set the environment variables os.environ['SDL_WINDOWID'] = str(self.GetHandle()) os.environ['SDL_VIDEODRIVER'] = 'windib' # do the pygame stuff after setting the environment variables import pygame pygame.display.init() # create the pygame window/screen screen = pygame.display.set_mode(464, 464) #(424,450) # start the thread instance self.thread = PG_thread(screen) self.thread.start() def __del__(self): self.thread.stop() And im trying to use that panel on an interface from Boa Constructor, here is the code: class frmMain(wx.Frame): def _init_ctrls(self, prnt): # generated method, don't edit wx.Frame.__init__(self, id=wxID_FRMMAIN, name='frmMain', parent=prnt, pos=wx.Point(660, 239), size=wx.Size(815, 661), style=wx.DEFAULT_FRAME_STYLE, title='Grupo 1 - Jogo de Damas') self._init_utils() self.SetClientSize(wx.Size(799, 623)) self.SetBackgroundColour(wx.Colour(225, 225, 225)) self.SetMinSize(wx.Size(784, 650)) self.Center(wx.BOTH) self.SetMenuBar(self.menuBar1) #here begins my code mysize = (464, 464) mypos = (16, 96) self.panelTabuleiro = PG_panel(wxID_FRMMAINPANELTABULEIRO, 'panelTabuleiro', self, mypos, mysize) The original that was auto-made by the Boa Constructor is the following: self.panelTabuleiro = wx.Panel(id=wxID_FRMMAINPANELTABULEIRO, name='panelTabuleiro', parent=self, pos=wx.Point(16, 96), size=wx.Size(464, 464), style=wx.TAB_TRAVERSAL) self.panelTabuleiro.SetBackgroundColour(wx.Colour(232, 249, 240)) self.panelTabuleiro.SetThemeEnabled(True) self.panelTabuleiro.SetHelpText('Tabuleiro') The error that it gives is: Type error: in method 'new_Panel', expected argument 1 of type 'wxWindow*1 Exception AttributeError: "'PG_panel' object has no attribute 'thread' in ignored Any thoughts ? I appreciate any help. Thank you.

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  • how to use listctrl in notebook wxPython

    - by ???
    I have one question.. wxPython listctrl in notebook I created 2 tab use notebook. I added button in first tab and added Listctrl in second tab. If i click the button, Add value in Listctrl to second tab. how to solve this problem? import wx class PageOne(wx.Panel): def __init__(self, parent): wx.Panel.__init__(self, parent) self.query_find_btn = wx.Button(self, 4, "BTN", (40,40)) self.Bind(wx.EVT_BUTTON, self.AddList, id = 4) def AddList(self, evt): self.list1.InsertStringItem(0,'Hello') class PageTwo(wx.Panel): def __init__(self, parent): wx.Panel.__init__(self, parent) self.list1 = wx.ListCtrl(self,-1,wx.Point(0,0),wx.Size(400,400),style=wx.LC_REPORT | wx.SUNKEN_BORDER) self.list1.InsertColumn(0,'values') class MyFrame(wx.Frame): def __init__(self, parent, id, title): wx.Frame.__init__(self,parent,id,title,size=(400,400),pos=wx.Point(100,100), style=wx.SYSTEM_MENU |wx.CAPTION ) p = wx.Panel(self) nb = wx.Notebook(p) MainFrame = PageOne(nb) SecondFrame = PageTwo(nb) nb.AddPage(MainFrame, "One") nb.AddPage(SecondFrame, "Two") sizer = wx.BoxSizer() sizer.Add(nb, 1, wx.EXPAND) p.SetSizer(sizer) class MyApp(wx.App): def OnInit(self): self.frame=MyFrame(None,-1,'Unknown.py') self.frame.Centre() self.frame.Show() return True if __name__ == '__main__': app = MyApp(False) app.MainLoop()

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  • Can't remove first node in linked list

    - by carlmonday
    I'm trying to make a linked list class in python (pointless I know, but it's a learning exercise), and the method I have written to remove a node doesn't work if I try to remove the first element of the linked list. If the node to be removed is anywhere else in the linked list the method works fine. Can someone give me some insight as to where I've gone wrong? Here's my code thus far: class Node: def __init__(self, data=None, next=None): self.data = data self.next = next def __repr__(self): return repr(self.data) def printNodes(self): while self: print self.data self = self.next def removeNode(self, datum): """removes node from linked list""" if self.data == datum: return self.next while self.next: if self.next.data == datum: self.next = self.next.next return self self = self.next

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  • Why subtract a value from itself (x - x) in Python?

    - by endolith
    In NumPy functions, there are often initial lines that do checking of variable types, forcing them to be certain types, etc. Can someone explain the point of these lines? What does subtracting a value from itself do? t,w = asarray(t), asarray(duty) w = asarray(w + (t-t)) t = asarray(t + (w-w))

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  • Dynamic Code for type casting Generic Types 'generically' in C#

    - by Rick Strahl
    C# is a strongly typed language and while that's a fundamental feature of the language there are more and more situations where dynamic types make a lot of sense. I've written quite a bit about how I use dynamic for creating new type extensions: Dynamic Types and DynamicObject References in C# Creating a dynamic, extensible C# Expando Object Creating a dynamic DataReader for dynamic Property Access Today I want to point out an example of a much simpler usage for dynamic that I use occasionally to get around potential static typing issues in C# code especially those concerning generic types. TypeCasting Generics Generic types have been around since .NET 2.0 I've run into a number of situations in the past - especially with generic types that don't implement specific interfaces that can be cast to - where I've been unable to properly cast an object when it's passed to a method or assigned to a property. Granted often this can be a sign of bad design, but in at least some situations the code that needs to be integrated is not under my control so I have to make due with what's available or the parent object is too complex or intermingled to be easily refactored to a new usage scenario. Here's an example that I ran into in my own RazorHosting library - so I have really no excuse, but I also don't see another clean way around it in this case. A Generic Example Imagine I've implemented a generic type like this: public class RazorEngine<TBaseTemplateType> where TBaseTemplateType : RazorTemplateBase, new() You can now happily instantiate new generic versions of this type with custom template bases or even a non-generic version which is implemented like this: public class RazorEngine : RazorEngine<RazorTemplateBase> { public RazorEngine() : base() { } } To instantiate one: var engine = new RazorEngine<MyCustomRazorTemplate>(); Now imagine that the template class receives a reference to the engine when it's instantiated. This code is fired as part of the Engine pipeline when it gets ready to execute the template. It instantiates the template and assigns itself to the template: var template = new TBaseTemplateType() { Engine = this } The problem here is that possibly many variations of RazorEngine<T> can be passed. I can have RazorTemplateBase, RazorFolderHostTemplateBase, CustomRazorTemplateBase etc. as generic parameters and the Engine property has to reflect that somehow. So, how would I cast that? My first inclination was to use an interface on the engine class and then cast to the interface.  Generally that works, but unfortunately here the engine class is generic and has a few members that require the template type in the member signatures. So while I certainly can implement an interface: public interface IRazorEngine<TBaseTemplateType> it doesn't really help for passing this generically templated object to the template class - I still can't cast it if multiple differently typed versions of the generic type could be passed. I have the exact same issue in that I can't specify a 'generic' generic parameter, since there's no underlying base type that's common. In light of this I decided on using object and the following syntax for the property (and the same would be true for a method parameter): public class RazorTemplateBase :MarshalByRefObject,IDisposable { public object Engine {get;set; } } Now because the Engine property is a non-typed object, when I need to do something with this value, I still have no way to cast it explicitly. What I really would need is: public RazorEngine<> Engine { get; set; } but that's not possible. Dynamic to the Rescue Luckily with the dynamic type this sort of thing can be mitigated fairly easily. For example here's a method that uses the Engine property and uses the well known class interface by simply casting the plain object reference to dynamic and then firing away on the properties and methods of the base template class that are common to all templates:/// <summary> /// Allows rendering a dynamic template from a string template /// passing in a model. This is like rendering a partial /// but providing the input as a /// </summary> public virtual string RenderTemplate(string template,object model) { if (template == null) return string.Empty; // if there's no template markup if(!template.Contains("@")) return template; // use dynamic to get around generic type casting dynamic engine = Engine; string result = engine.RenderTemplate(template, model); if (result == null) throw new ApplicationException("RenderTemplate failed: " + engine.ErrorMessage); return result; } Prior to .NET 4.0  I would have had to use Reflection for this sort of thing which would have a been a heck of a lot more verbose, but dynamic makes this so much easier and cleaner and in this case at least the overhead is negliable since it's a single dynamic operation on an otherwise very complex operation call. Dynamic as  a Bailout Sometimes this sort of thing often reeks of a design flaw, and I agree that in hindsight this could have been designed differently. But as is often the case this particular scenario wasn't planned for originally and removing the generic signatures from the base type would break a ton of other code in the framework. Given the existing fairly complex engine design, refactoring an interface to remove generic types just to make this particular code work would have been overkill. Instead dynamic provides a nice and simple and relatively clean solution. Now if there were many other places where this occurs I would probably consider reworking the code to make this cleaner but given this isolated instance and relatively low profile operation use of dynamic seems a valid choice for me. This solution really works anywhere where you might end up with an inheritance structure that doesn't have a common base or interface that is sufficient. In the example above I know what I'm getting but there's no common base type that I can cast to. All that said, it's a good idea to think about use of dynamic before you rush in. In many situations there are alternatives that can still work with static typing. Dynamic definitely has some overhead compared to direct static access of objects, so if possible we should definitely stick to static typing. In the example above the application already uses dynamics extensively for dynamic page page templating and passing models around so introducing dynamics here has very little additional overhead. The operation itself also fires of a fairly resource heavy operation where the overhead of a couple of dynamic member accesses are not a performance issue. So, what's your experience with dynamic as a bailout mechanism? © Rick Strahl, West Wind Technologies, 2005-2012Posted in CSharp   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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  • Postfix : error: unsupported dictionary type: mysql

    - by flavio.troja
    I've a problem w/ postfix problem: # tail -f /var/log/mail.err Aug 20 17:57:50 myserver postfix/smtpd[8243]: error: unsupported dictionary type: mysql Aug 20 17:57:50 myserver postfix/smtpd[8243]: error: unsupported dictionary type: mysql Aug 20 17:58:05 myserver postfix/smtpd[8244]: error: unsupported dictionary type: mysql Aug 20 17:58:05 myserver postfix/smtpd[8244]: error: unsupported dictionary type: mysql Aug 20 18:00:38 myserver postfix/smtpd[8277]: error: unsupported dictionary type: mysql Aug 20 18:00:38 myserver postfix/smtpd[8277]: error: unsupported dictionary type: mysql Aug 20 18:03:32 myserver postfix/smtpd[8320]: error: unsupported dictionary type: mysql Aug 20 18:03:32 myserver postfix/smtpd[8320]: error: unsupported dictionary type: mysql Aug 20 18:03:33 myserver postfix/trivial-rewrite[8322]: error: unsupported dictionary type: mysql Aug 20 18:03:33 myserver postfix/trivial-rewrite[8322]: error: unsupported dictionary type: mysql idea?

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  • Self-healing Cloud vs Failover Boxes

    - by IMB
    Now that self-healing cloud servers are becoming more and more popular, I am currently torn between the decision if I should setup a HAproxy failover for my VPS or if should save myself the trouble and just put my sites on a self-healing cloud server. Does it still make sense to setup your own failover system (HAproxy + 2 or more servers for example) when self healing cloud seems like a practical solution? They seem to do the same job or am I missing something?

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  • Self referencing userdata and garbage collection

    - by drtwox
    Because my userdata objects reference themselves, I need to delete and nil a variable for the garbage collector to work. Lua code: obj = object:new() -- -- Some time later obj:delete() -- Removes the self reference obj = nil -- Ready for collection C Code: typedef struct { int self; // Reference to the object // Other members and function references removed } Object; // Called from Lua to create a new object static int object_new( lua_State *L ) { Object *obj = lua_newuserdata( L, sizeof( Object ) ); // Create the 'self' reference, userdata is on the stack top obj->self = luaL_ref( L, LUA_REGISTRYINDEX ); // Put the userdata back on the stack before returning lua_rawgeti( L, LUA_REGISTRYINDEX, obj->self ); // The object pointer is also stored outside of Lua for processing in C return 1; } // Called by Lua to delete an object static int object_delete( lua_State *L ) { Object *obj = lua_touserdata( L, 1 ); // Remove the objects self reference luaL_unref( L, LUA_REGISTRYINDEX, obj->self ); return 0; } Is there some way I can set the object to nil in Lua, and have the delete() method called automatically? Alternatively, can the delete method nil all variables that reference the object? Can the self reference be made 'weak'?

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  • Changing pointer of self

    - by rob5408
    I have an object that I alloc/init like normal just to get a instance. Later in my application I want to load state from disk for that object. I figure I could unarchive my class (which conforms to NSCoding) and just swap where my instance points to. To this end I use this code... NSString* pathForDataFile = [self pathForDataFile]; if([[NSFileManager defaultManager] fileExistsAtPath:pathForDataFile] == YES) { NSLog(@"Save file exists"); NSData *data = [[NSMutableData alloc] initWithContentsOfFile:pathForDataFile]; NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data]; [data release]; Person *tempPerson = [unarchiver decodeObjectForKey:@"Person"]; [unarchiver finishDecoding]; [unarchiver release]; if (tempPerson) { [self release]; self = [tempPerson retain]; } } Now when I sprinkled some NSLogs throughout my application I noticed self.person: <Person: 0x3d01a10> (After I create the object with alloc/init) self: <Person: 0x3d01a10> (At the start of this method) tempPerson: <Person: 0x3b1b880> (When I create the tempPerson) self: <Person: 0x3b1b880> (after i point self to the location of the tempPerson) self.person: <Person: 0x3d01a10> (After the method back in the main program) What am I missing?

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  • SQL SERVER – OLEDB – Link Server – Wait Type – Day 23 of 28

    - by pinaldave
    When I decided to start writing about this wait type, the very first question that came to my mind was, “What does ‘OLEDB’ stand for?” A quick search on Wikipedia tells me that OLEDB means Object Linking and Embedding Database. (How many of you knew this?) Anyway, I found it very interesting that this wait type was in one of the top 10 wait types in many of the systems I have come across in my performance tuning experience. Books On-Line: ????OLEDB occurs when SQL Server calls the SQL Server Native Client OLE DB Provider. This wait type is not used for synchronization. Instead, it indicates the duration of calls to the OLE DB provider. OLEDB Explanation: This wait type primarily happens when Link Server or Remove Query has been executed. The most common case wherein this wait type is visible is during the execution of Linked Server. When SQL Server is retrieving data from the remote server, it uses OLEDB API to retrieve the data. It is possible that the remote system is not quick enough or the connection between them is not fast enough, leading SQL Server to wait for the result’s return from the remote (or external) server. This is the time OLEDB wait type occurs. Reducing OLEDB wait: Check the Link Server configuration. Checking Disk-Related Perfmon Counters Average Disk sec/Read (Consistent higher value than 4-8 millisecond is not good) Average Disk sec/Write (Consistent higher value than 4-8 millisecond is not good) Average Disk Read/Write Queue Length (Consistent higher value than benchmark is not good) At this point in time, I am not able to think of any more ways on reducing this wait type. Do you have any opinion about this subject? Please share it here and I will share your comment with the rest of the Community, and of course, with due credit unto you. Please read all the post in the Wait Types and Queue series. Note: The information presented here is from my experience and there is no way that I claim it to be accurate. I suggest reading Book OnLine for further clarification. All the discussion of Wait Stats in this blog is generic and varies from system to system. It is recommended that you test this on a development server before implementing it to a production server. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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