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  • What's the best way to stop multiple instances of a Windows app being launched?

    - by John
    Many Windows apps (like Skype or MSN for instance) don't let you start multiple instances, rather trying to run it a 2nd time just leaves the existing version running. Is this typically done in some simple way - the start-menu shortcut is a 'wrapper' app around the main app - or is there some registry magic you can do to delegate the problem to Windows itself? Specifically dealing with Win32 here (unmanaged C++) but happy to hear more general solutions as long as they are workable on Windows XP or alter.

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  • Downside to including headers in every source file (Objective-C)

    - by Michael Waterfall
    I'm currently including my AppDelegate.h and all of my category headers into every one of my source files using the MyApp_Prefix.pch prefix header, instead of manually #importing them only where they are used. The category methods and lots of compiler #define's in my app delegate are used in lots of places in my code. Is there any down side to this? Is it just that compilation will take longer?

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  • Is it multitasking?(c#3.0)

    - by Newbie
    Consider the below program factorThread = new Thread( new ThreadStart( delegate { Method1(); Method2(); } ) ); Is it that 2 threads are getting called parallely(multitasking) or a single thread is calling the methods sequentially? It's urgent. Thanks

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  • Animation in a table view cell

    - by theomen
    I'm not sure if it is possible to achieve, but my costumer wants that when user taps a table view cell, an animation of a UIView sliding from left to right is committed, leaving the content under the UIView visible. My concern is about how to trigger gesture recognizer added to the upper UIVIew for the animation and do not enter in conflict with didSelectRowatIndex: table view delegate method. Is it possible to achieve? Mant thanks!

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  • Is it possible to write syntax like - ()() ?

    - by dotnetdev
    I read in an ebook somewhere (which I'm desperate to find again), that, by using delegates, it is possible to write code which has syntax as follows: ()(); // where delegate proceeds this. Can anyone provide any details how this would be possible/in what situation this would occur? Thanks

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  • UnicodeEncodeError when uploading files in Django admin

    - by Samuel Linde
    Note: I asked this question on StackOverflow, but I realize this might be a more proper place to ask this kind of question. I'm trying to upload a file called 'Testaråäö.txt' via the Django admin app. I'm running Django 1.3.1 with Gunicorn 0.13.4 and Nginx 0.7.6.7 on a Debian 6 server. Database is PostgreSQL 8.4.9. Other Unicode data is saved to the database with no problem, so I guess the problem must be with the filesystem somehow. I've set http { charset utf-8; } in my nginx.conf. LC_ALL and LANG is set to 'sv_SE.UTF-8'. Running 'locale' verifies this. I even tried setting LC_ALL and LANG in my nginx init script just to make sure locale is set properly. Here's the traceback: Traceback (most recent call last): File "/srv/.virtualenvs/letebo/lib/python2.6/site-packages/django/core/handlers/base.py", line 111, in get_response response = callback(request, *callback_args, **callback_kwargs) File "/srv/.virtualenvs/letebo/lib/python2.6/site-packages/django/contrib/admin/options.py", line 307, in wrapper return self.admin_site.admin_view(view)(*args, **kwargs) File "/srv/.virtualenvs/letebo/lib/python2.6/site-packages/django/utils/decorators.py", line 93, in _wrapped_view response = view_func(request, *args, **kwargs) File "/srv/.virtualenvs/letebo/lib/python2.6/site-packages/django/views/decorators/cache.py", line 79, in _wrapped_view_func response = view_func(request, *args, **kwargs) File "/srv/.virtualenvs/letebo/lib/python2.6/site-packages/django/contrib/admin/sites.py", line 197, in inner return view(request, *args, **kwargs) File "/srv/django/letebo/app/cms/admin.py", line 81, in change_view return super(PageAdmin, self).change_view(request, obj_id) File "/srv/.virtualenvs/letebo/lib/python2.6/site-packages/django/utils/decorators.py", line 28, in _wrapper return bound_func(*args, **kwargs) File "/srv/.virtualenvs/letebo/lib/python2.6/site-packages/django/utils/decorators.py", line 93, in _wrapped_view response = view_func(request, *args, **kwargs) File "/srv/.virtualenvs/letebo/lib/python2.6/site-packages/django/utils/decorators.py", line 24, in bound_func return func(self, *args2, **kwargs2) File "/srv/.virtualenvs/letebo/lib/python2.6/site-packages/django/db/transaction.py", line 217, in inner res = func(*args, **kwargs) File "/srv/.virtualenvs/letebo/lib/python2.6/site-packages/django/contrib/admin/options.py", line 985, in change_view self.save_formset(request, form, formset, change=True) File "/srv/.virtualenvs/letebo/lib/python2.6/site-packages/django/contrib/admin/options.py", line 677, in save_formset formset.save() File "/srv/.virtualenvs/letebo/lib/python2.6/site-packages/django/forms/models.py", line 482, in save return self.save_existing_objects(commit) + self.save_new_objects(commit) File "/srv/.virtualenvs/letebo/lib/python2.6/site-packages/django/forms/models.py", line 613, in save_new_objects self.new_objects.append(self.save_new(form, commit=commit)) File "/srv/.virtualenvs/letebo/lib/python2.6/site-packages/django/forms/models.py", line 717, in save_new obj.save() File "/srv/.virtualenvs/letebo/lib/python2.6/site-packages/django/db/models/base.py", line 460, in save self.save_base(using=using, force_insert=force_insert, force_update=force_update) File "/srv/.virtualenvs/letebo/lib/python2.6/site-packages/django/db/models/base.py", line 504, in save_base self.save_base(cls=parent, origin=org, using=using) File "/srv/.virtualenvs/letebo/lib/python2.6/site-packages/django/db/models/base.py", line 543, in save_base for f in meta.local_fields if not isinstance(f, AutoField)] File "/srv/.virtualenvs/letebo/lib/python2.6/site-packages/django/db/models/fields/files.py", line 255, in pre_save file.save(file.name, file, save=False) File "/srv/.virtualenvs/letebo/lib/python2.6/site-packages/django/db/models/fields/files.py", line 92, in save self.name = self.storage.save(name, content) File "/srv/.virtualenvs/letebo/lib/python2.6/site-packages/django/core/files/storage.py", line 48, in save name = self.get_available_name(name) File "/srv/.virtualenvs/letebo/lib/python2.6/site-packages/django/core/files/storage.py", line 74, in get_available_name while self.exists(name): File "/srv/.virtualenvs/letebo/lib/python2.6/site-packages/django/core/files/storage.py", line 218, in exists return os.path.exists(self.path(name)) File "/srv/.virtualenvs/letebo/lib/python2.6/genericpath.py", line 18, in exists st = os.stat(path) UnicodeEncodeError: 'ascii' codec can't encode characters in position 52-54: ordinal not in range(128) I tried running Gunicorn with debugging turned on, and the file uploads without any problem at all. I suppose this must mean that the issue is with Nginx. Still beats me where to look, though. Here are the raw response headers from Gunicorn and Nginx, if it makes any sense: Gunicorn: HTTP/1.1 302 FOUND Server: gunicorn/0.13.4 Date: Thu, 09 Feb 2012 14:50:27 GMT Connection: close Transfer-Encoding: chunked Expires: Thu, 09 Feb 2012 14:50:27 GMT Vary: Cookie Last-Modified: Thu, 09 Feb 2012 14:50:27 GMT Location: http://my-server.se:8000/admin/cms/page/15/ Cache-Control: max-age=0 Content-Type: text/html; charset=utf-8 Set-Cookie: messages="yada yada yada"; Path=/ Nginx: HTTP/1.1 500 INTERNAL SERVER ERROR Server: nginx/0.7.67 Date: Thu, 09 Feb 2012 14:50:57 GMT Content-Type: text/html; charset=utf-8 Transfer-Encoding: chunked Connection: close Vary: Cookie 500 UPDATE: Both locale.getpreferredencoding() and sys.getfilesystemencoding() outputs 'UTF-8'. locale.getdefaultlocale() outputs ('sv_SE', 'UTF8'). This seem correct to me, so I'm still not sure why I keep getting these errors.

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  • Automating and deploying new linux servers

    - by luckytaxi
    I'm in the process of developing a method to automate new virtual machines into my environment. 90% of our machines are virtual but the process is similar for both physical and vmware based images. What I do now is I use cobbler to install the base OS. The kickstart script has post hooks to modify the yum repo and installs puppet and func. Once the servers are running, I manually add them into nagios and sign the certificate via the puppetmaster. I've since migrated most of the resources to use mysql as the backend. I wanted to see what others are doing and my goal for 2011 is to have puppet inventory the hardware into mysql, and somehow i'll script a python script to have nagios grab the info and automatically add it for monitoring purposes. It's kind of tedious to have to add each new server into nagios, puppet's dashboard, munin, etc...

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  • System says memory controller not available and doesn't boot?

    - by Martin
    Hello everybody, Recently I have had a MainBoard-problem. I've send my mainboard to service and today I got it back from the company. It is a Foxconn 520a mainboard. Now I have installed my exchanged mainboard. But now I have a problem. My system boots until the device list with IRQ entries appear. The system says "Verifying DMI-pool-data..." and nothing happens. The IRQ-device list shows that the memory-controller is not available. All other devices have got an IRQ. Bus No. Device No. Func No. Vendor/Device Class Device Class IRQ 0 0 0 10DE 0547 0500 Memory Controller NA Do you have any ideas where the problem could be? I already have disconnected all unnecessary devices like the hard disks. Perhaps it is a BIOS problem, but I don't know where I should look. Would be nice if there is any advice, Greetings, Martin

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  • Problem starting Compiz: symbol lookup error for libdecoration.so

    - by AniDev
    I run Ubuntu 10.10 (Maverick). I had removed Compiz 0.8.x from my system so I could try out Compiz 0.9.x. I then decided that I wanted Compiz 0.8.x back, so I installed the packages from aptitude. Now, when I try to start Compiz, I get this error: compiz: symbol lookup error: /usr/lib/compiz/libdecoration.so: undefined symbol: decor_property_to_quads Using the command "readelf /usr/lib/compiz/libdecoration.so -s", I see that that symbol is present: 24: 00000000 0 FUNC GLOBAL DEFAULT UND decor_property_to_quads Aptitude reports that my Compiz core packages (like compiz, compiz-core, compiz-plugins, etc.) are at version 1:0.8.6-0ubuntu9.1. Does anyone have any ideas why Compiz is reporting this error, and/or what I can do to fix it? I cannot run Compiz, because this error causes Compiz to abort, even if the "Window Decoration" plugin is not enabled.

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  • How can I get GrowlTunes to Launch whenever iTunes Launches?

    - by Orion751
    I think I would be able to do this by modifying iTunes' launch services. Any idea how to go about that? Would editing its info.plist file in a manner similar to below do what I'm looking for? <keyLSOpenApplication</key <string?</string EDIT: Would http://developer.apple.com/library/mac/#documentation/Carbon/Reference/LaunchServicesReference/Reference/reference.html%23//apple_ref/c/func/LSOpenApplication provide any hints? EDIT2: Last.fm's official Mac Scrobbler (http://www.last.fm/download) is a perfect example of the functionality that I'm looking for.

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  • How does this decorator make a call to the 'register' method?

    - by BryanWheelock
    I'm trying to understand what is going on in the decorator @not_authenticated. The next step in the TraceRoute is to the method 'register' which is also located in django_authopenid/views.py which I just don't understand because I don't see anywhere that register is even mentioned in signin() How is the method 'register' called? def not_authenticated(func): """ decorator that redirect user to next page if he is already logged.""" def decorated(request, *args, **kwargs): if request.user.is_authenticated(): next = request.GET.get("next", "/") return HttpResponseRedirect(next) return func(request, *args, **kwargs) return decorated @not_authenticated def signin(request,newquestion=False,newanswer=False): """ signin page. It manage the legacy authentification (user/password) and authentification with openid. url: /signin/ template : authopenid/signin.htm """ request.encoding = 'UTF-8' on_failure = signin_failure next = clean_next(request.GET.get('next')) form_signin = OpenidSigninForm(initial={'next':next}) form_auth = OpenidAuthForm(initial={'next':next}) if request.POST: if 'bsignin' in request.POST.keys() or 'openid_username' in request.POST.keys(): form_signin = OpenidSigninForm(request.POST) if form_signin.is_valid(): next = clean_next(form_signin.cleaned_data.get('next')) sreg_req = sreg.SRegRequest(optional=['nickname', 'email']) redirect_to = "%s%s?%s" % ( get_url_host(request), reverse('user_complete_signin'), urllib.urlencode({'next':next}) ) return ask_openid(request, form_signin.cleaned_data['openid_url'], redirect_to, on_failure=signin_failure, sreg_request=sreg_req) elif 'blogin' in request.POST.keys(): # perform normal django authentification form_auth = OpenidAuthForm(request.POST) if form_auth.is_valid(): user_ = form_auth.get_user() login(request, user_) next = clean_next(form_auth.cleaned_data.get('next')) return HttpResponseRedirect(next) question = None if newquestion == True: from forum.models import AnonymousQuestion as AQ session_key = request.session.session_key qlist = AQ.objects.filter(session_key=session_key).order_by('-added_at') if len(qlist) > 0: question = qlist[0] answer = None if newanswer == True: from forum.models import AnonymousAnswer as AA session_key = request.session.session_key alist = AA.objects.filter(session_key=session_key).order_by('-added_at') if len(alist) > 0: answer = alist[0] return render('authopenid/signin.html', { 'question':question, 'answer':answer, 'form1': form_auth, 'form2': form_signin, 'msg': request.GET.get('msg',''), 'sendpw_url': reverse('user_sendpw'), }, context_instance=RequestContext(request)) Looking at the request, it seems that account/register/ does reference the register method with 'PATH_INFO': u'/account/register/' Here is the request: <WSGIRequest GET:<QueryDict: {}>, POST:<QueryDict: {u'username': [u'BryanWheelock'], u'email': [u'[email protected]'], u'bnewaccount': [u'Signup']}>, COOKIES:{'__utma': '127460431.1218630960.1266769637.1266769637.1266864494.2', '__utmb': '127460431.3.10.1266864494', '__utmc': '127460431', '__utmz': '127460431.1266769637.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none)', 'sessionid': 'fb15ee538320170a22d3a3a324aad968'}, META:{'CONTENT_LENGTH': '74', 'CONTENT_TYPE': 'application/x-www-form-urlencoded', 'DOCUMENT_ROOT': '/usr/local/apache2/htdocs', 'GATEWAY_INTERFACE': 'CGI/1.1', 'HTTP_ACCEPT': 'application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5', 'HTTP_ACCEPT_CHARSET': 'ISO-8859-1,utf-8;q=0.7,*;q=0.3', 'HTTP_ACCEPT_ENCODING': 'gzip,deflate,sdch', 'HTTP_ACCEPT_LANGUAGE': 'en-US,en;q=0.8', 'HTTP_CACHE_CONTROL': 'max-age=0', 'HTTP_CONNECTION': 'close', 'HTTP_COOKIE': '__utmz=127460431.1266769637.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none); __utma=127460431.1218630960.1266769637.1266769637.1266864494.2; __utmc=127460431; __utmb=127460431.3.10.1266864494; sessionid=fb15ee538320170a22d3a3a324aad968', 'HTTP_HOST': 'workproject.com', 'HTTP_ORIGIN': 'http://workproject.com', 'HTTP_REFERER': 'http://workproject.com/account/signin/complete/?next=%2F&janrain_nonce=2010-02-22T18%3A49%3A53ZG2KXci&openid.ns=http%3A%2F%2Fspecs.openid.net%2Fauth%2F2.0&openid.mode=id_res&openid.op_endpoint=https%3A%2F%2Fwww.google.com%2Faccounts%2Fo8%2Fud&openid.response_nonce=2010-02-22T18%3A49%3A53Znxxxxxxxxxw&openid.return_to=http%3A%2F%2Fworkproject.com%2Faccount%2Fsignin%2Fcomplete%2F%3Fnext%3D%252F%26janrain_nonce%3D2010-02-22T18%253A49%253A53ZG2KXci&openid.assoc_handle=AOQobUepU4xs-kGg5LiyLzfN3RYv0I0Jocgjf_1odT4RR9zfMFpQVpMg&openid.signed=op_endpoint%2Cclaimed_id%2Cidentity%2Creturn_to%2Cresponse_nonce%2Cassoc_handle&openid.sig=Jf76i2RNhqpLTJMjeQ0nnQz6fgA%3D&openid.identity=https%3A%2F%2Fwww.google.com%2Faccounts%2Fo8%2Fid%3Fid%3DAItxxxxxxxxxs9CxHQ3PrHw_N5_3j1HM&openid.claimed_id=https%3A%2F%2Fwww.google.com%2Faccounts%2Fo8%2Fid%3Fid%3DAItOaxxxxxxxxxxx4s9CxHQ3PrHw_N5_3j1HM', 'HTTP_USER_AGENT': 'Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_5_8; en-US) AppleWebKit/532.9 (KHTML, like Gecko) Chrome/5.0.307.7 Safari/532.9', 'HTTP_X_FORWARDED_FOR': '96.8.31.235', 'PATH': '/usr/bin:/bin', 'PATH_INFO': u'/account/register/', 'PATH_TRANSLATED': '/home/spirituality/webapps/work/spirit_app.wsgi/account/register/', 'QUERY_STRING': '', 'REMOTE_ADDR': '127.0.0.1', 'REMOTE_PORT': '59956', 'REQUEST_METHOD': 'POST', 'REQUEST_URI': '/account/register/', 'SCRIPT_FILENAME': '/home/spirituality/webapps/spirituality/spirit_app.wsgi', 'SCRIPT_NAME': u'', 'SERVER_ADDR': '127.0.0.1', 'SERVER_ADMIN': '[no address given]', 'SERVER_NAME': 'workproject.com', 'SERVER_PORT': '80', 'SERVER_PROTOCOL': 'HTTP/1.0', 'SERVER_SIGNATURE': '', 'SERVER_SOFTWARE': 'Apache/2.2.12 (Unix) mod_wsgi/2.5 Python/2.5.4', 'mod_wsgi.application_group': 'www.workProject.com|', 'mod_wsgi.callable_object': 'application', 'mod_wsgi.listener_host': '', 'mod_wsgi.listener_port': '25931', 'mod_wsgi.process_group': '', 'mod_wsgi.reload_mechanism': '0', 'mod_wsgi.script_reloading': '1', 'mod_wsgi.version': (2, 5), 'wsgi.errors': <mod_wsgi.Log object at 0xb7ce0038>, 'wsgi.file_wrapper': <built-in method file_wrapper of mod_wsgi.Adapter object at 0xb7e94b18>, 'wsgi.input': <mod_wsgi.Input object at 0x999cc78>, 'wsgi.multiprocess': True, 'wsgi.multithread': False, 'wsgi.run_once': False, 'wsgi.url_scheme': 'http', 'wsgi.version': (1, 0)}>

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  • building median for each string in IList<IDictionary<string, double>>

    - by Oliver
    Actually i have a little brain bender and and just can't find the right direction to get it to work: Given is an IList<IDictionary<string, double>> and it is filled as followed: Name|Value ----+----- "x" | 3.8 "y" | 4.2 "z" | 1.5 ----+----- "x" | 7.2 "y" | 2.9 "z" | 1.3 ----+----- ... | ... To fill this up with some random data i used the following methods: var list = CreateRandomPoints(new string[] { "x", "y", "z" }, 20); This will work as followed: private IList<IDictionary<string, double>> CreateRandomPoints(string[] variableNames, int count) { var list = new List<IDictionary<string, double>>(count); list.AddRange(CreateRandomPoints(variableNames).Take(count)); return list; } private IEnumerable<IDictionary<string, double>> CreateRandomPoints(string[] variableNames) { while (true) yield return CreateRandomLine(variableNames); } private IDictionary<string, double> CreateRandomLine(string[] variableNames) { var dict = new Dictionary<string, double>(variableNames.Length); foreach (var variable in variableNames) { dict.Add(variable, _Rand.NextDouble() * 10); } return dict; } Also i can say that it is already ensured that every Dictionary within the list contains the same keys (but from list to list the names and count of the keys can change). So that's what i got. Now to the things i need: I'd like to get the median (or any other math aggregate operation) of each Key within all the dictionaries, so that my function to call would look something like: IDictionary<string, double> GetMedianOfRows(this IList<IDictionary<string, double>> list) The best would be to give some kind of aggregate operation as a parameter to the function to make it more generic (don't know if the func has the correct parameters, but should imagine what i'd like to do): private IDictionary<string, double> Aggregate(this IList<IDictionary<string, double>> list, Func<IEnumerable<double>, double> aggregator) Also my actual biggest problem is to do the job with a single iteration over the list, cause if within the list are 20 variables with 1000 values i don't like to iterate 20 times over the list. Instead i would go one time over the list and compute all twenty variables at once (The biggest advantage of doing it that way would be to use this also as IEnumerable<T> on any part of the list in a later step). So here is the code i already got: public static IDictionary<string, double> GetMedianOfRows(this IList<IDictionary<string, double>> list) { //Check of parameters is left out! //Get first item for initialization of result dictionary var firstItem = list[0]; //Create result dictionary and fill in variable names var dict = new Dictionary<string, double>(firstItem.Count); //Iterate over the whole list foreach (IDictionary<string, double> row in list) { //Iterate over each key/value pair within the list foreach (var kvp in row) { //How to determine median of all values? } } return dict; } Just to be sure here is a little explanation about the Median.

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  • SQLAlchemy session management in long-running process

    - by codeape
    Scenario: A .NET-based application server (Wonderware IAS/System Platform) hosts automation objects that communicate with various equipment on the factory floor. CPython is hosted inside this application server (using Python for .NET). The automation objects have scripting functionality built-in (using a custom, .NET-based language). These scripts call Python functions. The Python functions are part of a system to track Work-In-Progress on the factory floor. The purpose of the system is to track the produced widgets along the process, ensure that the widgets go through the process in the correct order, and check that certain conditions are met along the process. The widget production history and widget state is stored in a relational database, this is where SQLAlchemy plays its part. For example, when a widget passes a scanner, the automation software triggers the following script (written in the application server's custom scripting language): ' wiget_id and scanner_id provided by automation object ' ExecFunction() takes care of calling a CPython function retval = ExecFunction("WidgetScanned", widget_id, scanner_id); ' if the python function raises an Exception, ErrorOccured will be true ' in this case, any errors should cause the production line to stop. if (retval.ErrorOccured) then ProductionLine.Running = False; InformationBoard.DisplayText = "ERROR: " + retval.Exception.Message; InformationBoard.SoundAlarm = True end if; The script calls the WidgetScanned python function: # pywip/functions.py from pywip.database import session from pywip.model import Widget, WidgetHistoryItem from pywip import validation, StatusMessage from datetime import datetime def WidgetScanned(widget_id, scanner_id): widget = session.query(Widget).get(widget_id) validation.validate_widget_passed_scanner(widget, scanner) # raises exception on error widget.history.append(WidgetHistoryItem(timestamp=datetime.now(), action=u"SCANNED", scanner_id=scanner_id)) widget.last_scanner = scanner_id widget.last_update = datetime.now() return StatusMessage("OK") # ... there are a dozen similar functions My question is: How do I best manage SQLAlchemy sessions in this scenario? The application server is a long-running process, typically running months between restarts. The application server is single-threaded. Currently, I do it the following way: I apply a decorator to the functions I make avaliable to the application server: # pywip/iasfunctions.py from pywip import functions def ias_session_handling(func): def _ias_session_handling(*args, **kwargs): try: retval = func(*args, **kwargs) session.commit() return retval except: session.rollback() raise return _ias_session_handling # ... actually I populate this module with decorated versions of all the functions in pywip.functions dynamically WidgetScanned = ias_session_handling(functions.WidgetScanned) Question: Is the decorator above suitable for handling sessions in a long-running process? Should I call session.remove()? The SQLAlchemy session object is a scoped session: # pywip/database.py from sqlalchemy.orm import scoped_session, sessionmaker session = scoped_session(sessionmaker()) I want to keep the session management out of the basic functions. For two reasons: There is another family of functions, sequence functions. The sequence functions call several of the basic functions. One sequence function should equal one database transaction. I need to be able to use the library from other environments. a) From a TurboGears web application. In that case, session management is done by TurboGears. b) From an IPython shell. In that case, commit/rollback will be explicit. (I am truly sorry for the long question. But I felt I needed to explain the scenario. Perhaps not necessary?)

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  • Best style for Python programs: what do you suggest?

    - by Noctis Skytower
    A friend of mine wanted help learning to program, so he gave me all the programs that he wrote for his previous classes. The last program that he wrote was an encryption program, and after rewriting all his programs in Python, this is how his encryption program turned out (after adding my own requirements). #! /usr/bin/env python ################################################################################ """\ CLASS INFORMATION ----------------- Program Name: Program 11 Programmer: Stephen Chappell Instructor: Stephen Chappell for CS 999-0, Python Due Date: 17 May 2010 DOCUMENTATION ------------- This is a simple encryption program that can encode and decode messages.""" ################################################################################ import sys KEY_FILE = 'Key.txt' BACKUP = '''\ !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNO\ PQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~ _@/6-UC'GzaV0%5Mo9g+yNh8b">Bi=<Lx [sQn#^R.D2Xc(\ Jm!4e${lAEWud&t7]H\`}pvPw)FY,Z~?qK|3SOfk*:1;jTrI''' ################################################################################ def main(): "Run the program: loads key, runs processing loop, and saves key." encode_map, decode_map = load_key(KEY_FILE) try: run_interface_loop(encode_map, decode_map) except SystemExit: pass save_key(KEY_FILE, encode_map) def run_interface_loop(encode_map, decode_map): "Shows the menu and runs the appropriate command." print('This program handles encryption via a customizable key.') while True: print('''\ MENU ==== (1) Encode (2) Decode (3) Custom (4) Finish''') switch = get_character('Select: ', tuple('1234')) FUNC[switch](encode_map, decode_map) def get_character(prompt, choices): "Gets a valid menu option and returns it." while True: sys.stdout.write(prompt) sys.stdout.flush() line = sys.stdin.readline()[:-1] if not line: sys.exit() if line in choices: return line print(repr(line), 'is not a valid choice.') ################################################################################ def load_key(filename): "Gets the key file data and returns encoding/decoding dictionaries." plain, cypher = open_file(filename) return dict(zip(plain, cypher)), dict(zip(cypher, plain)) def open_file(filename): "Load the keys and tries to create it when not available." while True: try: with open(filename) as file: plain, cypher = file.read().split('\n') return plain, cypher except: with open(filename, 'w') as file: file.write(BACKUP) def save_key(filename, encode_map): "Dumps the map into two buffers and saves them to the key file." plain = cypher = str() for p, c in encode_map.items(): plain += p cypher += c with open(filename, 'w') as file: file.write(plain + '\n' + cypher) ################################################################################ def encode(encode_map, decode_map): "Encodes message for the user." print('Enter your message to encode (EOF when finished).') message = get_message() for char in message: sys.stdout.write(encode_map[char] if char in encode_map else char) def decode(encode_map, decode_map): "Decodes message for the user." print('Enter your message to decode (EOF when finished).') message = get_message() for char in message: sys.stdout.write(decode_map[char] if char in decode_map else char) def custom(encode_map, decode_map): "Allows user to edit the encoding/decoding dictionaries." plain, cypher = get_new_mapping() for p, c in zip(plain, cypher): encode_map[p] = c decode_map[c] = p ################################################################################ def get_message(): "Gets and returns text entered by the user (until EOF)." buffer = [] while True: line = sys.stdin.readline() if line: buffer.append(line) else: return ''.join(buffer) def get_new_mapping(): "Prompts for strings to edit encoding/decoding maps." while True: plain = get_unique_chars('What do you want to encode from?') cypher = get_unique_chars('What do you want to encode to?') if len(plain) == len(cypher): return plain, cypher print('Both lines should have the same length.') def get_unique_chars(prompt): "Gets strings that only contain unique characters." print(prompt) while True: line = input() if len(line) == len(set(line)): return line print('There were duplicate characters: please try again.') ################################################################################ # This map is used for dispatching commands in the interface loop. FUNC = {'1': encode, '2': decode, '3': custom, '4': lambda a, b: sys.exit()} ################################################################################ if __name__ == '__main__': main() For all those Python programmers out there, your help is being requested. How should the formatting (not necessarily the coding by altered to fit Python's style guide? My friend does not need to be learning things that are not correct. If you have suggestions on the code, feel free to post them to this wiki as well.

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  • Differing styles in Python program: what do you suggest?

    - by Noctis Skytower
    A friend of mine wanted help learning to program, so he gave me all the programs that he wrote for his previous classes. The last program that he wrote was an encryption program, and after rewriting all his programs in Python, this is how his encryption program turned out (after adding my own requirements). #! /usr/bin/env python ################################################################################ """\ CLASS INFORMATION ----------------- Program Name: Program 11 Programmer: Stephen Chappell Instructor: Stephen Chappell for CS 999-0, Python Due Date: 17 May 2010 DOCUMENTATION ------------- This is a simple encryption program that can encode and decode messages.""" ################################################################################ import sys KEY_FILE = 'Key.txt' BACKUP = '''\ !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNO\ PQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~ _@/6-UC'GzaV0%5Mo9g+yNh8b">Bi=<Lx [sQn#^R.D2Xc(\ Jm!4e${lAEWud&t7]H\`}pvPw)FY,Z~?qK|3SOfk*:1;jTrI''' ################################################################################ def main(): "Run the program: loads key, runs processing loop, and saves key." encode_map, decode_map = load_key(KEY_FILE) try: run_interface_loop(encode_map, decode_map) except SystemExit: pass save_key(KEY_FILE, encode_map) def run_interface_loop(encode_map, decode_map): "Shows the menu and runs the appropriate command." print('This program handles encryption via a customizable key.') while True: print('''\ MENU ==== (1) Encode (2) Decode (3) Custom (4) Finish''') switch = get_character('Select: ', tuple('1234')) FUNC[switch](encode_map, decode_map) def get_character(prompt, choices): "Gets a valid menu option and returns it." while True: sys.stdout.write(prompt) sys.stdout.flush() line = sys.stdin.readline()[:-1] if not line: sys.exit() if line in choices: return line print(repr(line), 'is not a valid choice.') ################################################################################ def load_key(filename): "Gets the key file data and returns encoding/decoding dictionaries." plain, cypher = open_file(filename) return dict(zip(plain, cypher)), dict(zip(cypher, plain)) def open_file(filename): "Load the keys and tries to create it when not available." while True: try: with open(filename) as file: plain, cypher = file.read().split('\n') return plain, cypher except: with open(filename, 'w') as file: file.write(BACKUP) def save_key(filename, encode_map): "Dumps the map into two buffers and saves them to the key file." plain = cypher = str() for p, c in encode_map.items(): plain += p cypher += c with open(filename, 'w') as file: file.write(plain + '\n' + cypher) ################################################################################ def encode(encode_map, decode_map): "Encodes message for the user." print('Enter your message to encode (EOF when finished).') message = get_message() for char in message: sys.stdout.write(encode_map[char] if char in encode_map else char) def decode(encode_map, decode_map): "Decodes message for the user." print('Enter your message to decode (EOF when finished).') message = get_message() for char in message: sys.stdout.write(decode_map[char] if char in decode_map else char) def custom(encode_map, decode_map): "Allows user to edit the encoding/decoding dictionaries." plain, cypher = get_new_mapping() for p, c in zip(plain, cypher): encode_map[p] = c decode_map[c] = p ################################################################################ def get_message(): "Gets and returns text entered by the user (until EOF)." buffer = [] while True: line = sys.stdin.readline() if line: buffer.append(line) else: return ''.join(buffer) def get_new_mapping(): "Prompts for strings to edit encoding/decoding maps." while True: plain = get_unique_chars('What do you want to encode from?') cypher = get_unique_chars('What do you want to encode to?') if len(plain) == len(cypher): return plain, cypher print('Both lines should have the same length.') def get_unique_chars(prompt): "Gets strings that only contain unique characters." print(prompt) while True: line = input() if len(line) == len(set(line)): return line print('There were duplicate characters: please try again.') ################################################################################ # This map is used for dispatching commands in the interface loop. FUNC = {'1': encode, '2': decode, '3': custom, '4': lambda a, b: sys.exit()} ################################################################################ if __name__ == '__main__': main() For all those Python programmers out there, your help is being requested. How should the formatting (not necessarily the coding by altered to fit Python's style guide? My friend does not need to be learning things that are not correct. If you have suggestions on the code, feel free to post them to this wiki as well.

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  • Entity Framework Generic Repository Error

    - by Jeff Ancel
    I am trying to create a very generic generics repository for my Entity Framework repository that has the basic CRUD statements and uses an Interface. I have hit a brick wall head first and been knocked over. Here is my code, written in a console application, using a Entity Framework Model, with a table named Hurl. Simply trying to pull back the object by its ID. Here is the full application code. using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Data.Objects; using System.Linq.Expressions; using System.Reflection; using System.Data.Objects.DataClasses; namespace GenericsPlay { class Program { static void Main(string[] args) { var hs = new HurlRepository(new hurladminEntity()); var hurl = hs.Load<Hurl>(h => h.Id == 1); Console.Write(hurl.ShortUrl); Console.ReadLine(); } } public interface IHurlRepository { T Load<T>(Expression<Func<T, bool>> expression); } public class HurlRepository : IHurlRepository, IDisposable { private ObjectContext _objectContext; public HurlRepository(ObjectContext objectContext) { _objectContext = objectContext; } public ObjectContext ObjectContext { get { return _objectContext; } } private Type GetBaseType(Type type) { Type baseType = type.BaseType; if (baseType != null && baseType != typeof(EntityObject)) { return GetBaseType(type.BaseType); } return type; } private bool HasBaseType(Type type, out Type baseType) { Type originalType = type.GetType(); baseType = GetBaseType(type); return baseType != originalType; } public IQueryable<T> GetQuery<T>() { Type baseType; if (HasBaseType(typeof(T), out baseType)) { return this.ObjectContext.CreateQuery<T>("[" + baseType.Name.ToString() + "]").OfType<T>(); } else { return this.ObjectContext.CreateQuery<T>("[" + typeof(T).Name.ToString() + "]"); } } public T Load<T>(Expression<Func<T, bool>> whereCondition) { return this.GetQuery<T>().Where(whereCondition).First(); } public void Dispose() { if (_objectContext != null) { _objectContext.Dispose(); } } } } Here is the error that I am getting: System.Data.EntitySqlException was unhandled Message="'Hurl' could not be resolved in the current scope or context. Make sure that all referenced variables are in scope, that required schemas are loaded, and that namespaces are referenced correctly., near escaped identifier, line 3, column 1." Source="System.Data.Entity" Column=1 ErrorContext="escaped identifier" ErrorDescription="'Hurl' could not be resolved in the current scope or context. Make sure that all referenced variables are in scope, that required schemas are loaded, and that namespaces are referenced correctly." This is where I am attempting to extract this information from. http://blog.keithpatton.com/2008/05/29/Polymorphic+Repository+For+ADONet+Entity+Framework.aspx

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  • Dynamic LINQ in an Assembly Near By

    - by Ricardo Peres
    You may recall my post on Dynamic LINQ. I said then that you had to download Microsoft's samples and compile the DynamicQuery project (or just grab my copy), but there's another way. It turns out Microsoft included the Dynamic LINQ classes in the System.Web.Extensions assembly, not the one from ASP.NET 2.0, but the one that was included with ASP.NET 3.5! The only problem is that all types are private: Here's how to use it: Assembly asm = typeof(UpdatePanel).Assembly; Type dynamicExpressionType = asm.GetType("System.Web.Query.Dynamic.DynamicExpression"); MethodInfo parseLambdaMethod = dynamicExpressionType.GetMethods(BindingFlags.Public | BindingFlags.Static).Where(m = (m.Name == "ParseLambda") && (m.GetParameters().Length == 2)).Single().MakeGenericMethod(typeof(DateTime), typeof(Boolean)); Func filterExpression = (parseLambdaMethod.Invoke(null, new Object [] { "Year == 2010", new Object [ 0 ] }) as Expression).Compile(); List list = new List { new DateTime(2010, 1, 1), new DateTime(1999, 1, 12), new DateTime(1900, 10, 10), new DateTime(1900, 2, 20), new DateTime(2012, 5, 5), new DateTime(2012, 1, 20) }; IEnumerable filteredDates = list.Where(filterExpression); SyntaxHighlighter.config.clipboardSwf = 'http://alexgorbatchev.com/pub/sh/2.0.320/scripts/clipboard.swf'; SyntaxHighlighter.brushes.CSharp.aliases = ['c#', 'c-sharp', 'csharp']; SyntaxHighlighter.all();

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  • Using jQuery Live instead of jQuery Hover function

    - by hajan
    Let’s say we have a case where we need to create mouseover / mouseout functionality for a list which will be dynamically filled with data on client-side. We can use jQuery hover function, which handles the mouseover and mouseout events with two functions. See the following example: <!DOCTYPE html> <html lang="en"> <head id="Head1" runat="server">     <title>jQuery Mouseover / Mouseout Demo</title>     <script type="text/javascript" src="http://ajax.aspnetcdn.com/ajax/jquery/jquery-1.4.4.js"></script>     <style type="text/css">         .hover { color:Red; cursor:pointer;}     </style>     <script type="text/javascript">         $(function () {             $("li").hover(               function () {                   $(this).addClass("hover");               },               function () {                   $(this).removeClass("hover");               });         });     </script> </head> <body>     <form id="form2" runat="server">     <ul>         <li>Data 1</li>         <li>Data 2</li>         <li>Data 3</li>         <li>Data 4</li>         <li>Data 5</li>         <li>Data 6</li>     </ul>     </form> </body> </html> Now, if you have situation where you want to add new data dynamically... Lets say you have a button to add new item in the list. Add the following code right bellow the </ul> tag <input type="text" id="txtItem" /> <input type="button" id="addNewItem" value="Add New Item" /> And add the following button click functionality: //button add new item functionality $("#addNewItem").click(function (event) {     event.preventDefault();     $("<li>" + $("#txtItem").val() + "</li>").appendTo("ul"); }); The mouse over effect won't work for the newly added items. Therefore, we need to use live or delegate function. These both do the same job. The main difference is that for some cases delegate is considered a bit faster, and can be used in chaining. In our case, we can use both. I will use live function. $("li").live("mouseover mouseout",   function (event) {       if (event.type == "mouseover") $(this).addClass("hover");       else $(this).removeClass("hover");   }); The complete code is: <!DOCTYPE html> <html lang="en"> <head id="Head1" runat="server">     <title>jQuery Mouseover / Mouseout Demo</title>     <script type="text/javascript" src="http://ajax.aspnetcdn.com/ajax/jquery/jquery-1.4.4.js"></script>     <style type="text/css">         .hover { color:Red; cursor:pointer;}     </style>     <script type="text/javascript">         $(function () {             $("li").live("mouseover mouseout",               function (event) {                   if (event.type == "mouseover") $(this).addClass("hover");                   else $(this).removeClass("hover");               });             //button add new item functionality             $("#addNewItem").click(function (event) {                 event.preventDefault();                 $("<li>" + $("#txtItem").val() + "</li>").appendTo("ul");             });         });     </script> </head> <body>     <form id="form2" runat="server">     <ul>         <li>Data 1</li>         <li>Data 2</li>         <li>Data 3</li>         <li>Data 4</li>         <li>Data 5</li>         <li>Data 6</li>     </ul>          <input type="text" id="txtItem" />     <input type="button" id="addNewItem" value="Add New Item" />     </form> </body> </html> So, basically when replacing hover with live, you see we use the mouseover and mouseout names for both events. Check the working demo which is available HERE. Hope this was useful blog for you. Hope it’s helpful. HajanReference blog: http://codeasp.net/blogs/hajan/microsoft-net/1260/using-jquery-live-instead-of-jquery-hover-function

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  • Python HTTPS requests (urllib2) fails on Ubuntu 12.04 without proxy

    - by Pablo
    I have an little app I wrote in Python and it used to work... until yesterday, when it suddenly started giving me an error in a HTTPS connection. I don't remember if there was an update, but both Python 2.7.3rc2 and Python 3.2 are failing just the same. I googled it and found out that this happens when people are behind a proxy, but I'm not (and nothing have changed in my network since the last time it worked). My syster's computer running windows and Python 2.7.2 has no problems (in the same network). response = urllib2.urlopen(url).read() File "/usr/lib/python2.7/urllib2.py", line 126, in urlopen return _opener.open(url, data, timeout) File "/usr/lib/python2.7/urllib2.py", line 400, in open response = self._open(req, data) File "/usr/lib/python2.7/urllib2.py", line 418, in _open '_open', req) File "/usr/lib/python2.7/urllib2.py", line 378, in _call_chain result = func(*args) File "/usr/lib/python2.7/urllib2.py", line 1215, in https_open return self.do_open(httplib.HTTPSConnection, req) File "/usr/lib/python2.7/urllib2.py", line 1177, in do_open raise URLError(err) urllib2.URLError: <urlopen error [Errno 8] _ssl.c:504: EOF occurred in violation of protocol> What's wrong? Any help is appreciated. PS.: Older python versions don't work either, not in my system and not in a live session from USB, but DO work in a Ubuntu 11.10 live session.

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  • How do I get vmbuilder to progress?

    - by Avery Chan
    I've used the following command to create my vm: vmbuilder kvm ubuntu --verbose --suite=precise --flavour=virtual --arch=amd64 -o --libvirt=qemu:///system --tmpfs=- --ip=192.168.2.1 --part=/home/shared/vm1/vmbuilder.partition --templates=/home/shared/vm1/templates --user=vadmin --name=VM-Administrator --pass=vpass --addpkg=vim-nox --addpkg=unattended-upgrades --addpkg=acpid --firstboot=/home/shared/vm1/boot.sh --mem=256 --hostname=chameleon --bridge=br0 I've been trying to follow the direction here. My system just outputs this and it hangs at the last line: 2012-06-26 18:08:29,225 INFO : Mounting tmpfs under /tmp/tmpJbf1dZtmpfs 2012-06-26 18:08:29,234 INFO : Calling hook: preflight_check 2012-06-26 18:08:29,243 INFO : Calling hook: set_defaults 2012-06-26 18:08:29,244 INFO : Calling hook: bootstrap How can I get vmbuilder to continue the process instead of dying right here? I'm running 12.04. EDIT: Adding some additional output details When I ^C to get out of the hang I see this: ^C2012-06-26 18:19:29,622 INFO : Unmounting tmpfs from /tmp/tmpJbf1dZtmpfs Traceback (most recent call last): File "/usr/bin/vmbuilder", line 24, in <module> cli.main() File "/usr/lib/python2.7/dist-packages/VMBuilder/contrib/cli.py", line 216, in main distro.build_chroot() File "/usr/lib/python2.7/dist-packages/VMBuilder/distro.py", line 83, in build_chroot self.call_hooks('bootstrap') File "/usr/lib/python2.7/dist-packages/VMBuilder/distro.py", line 67, in call_hooks call_hooks(self, *args, **kwargs) File "/usr/lib/python2.7/dist-packages/VMBuilder/util.py", line 165, in call_hooks getattr(context, func, log_no_such_method)(*args, **kwargs) File "/usr/lib/python2.7/dist-packages/VMBuilder/plugins/ubuntu/distro.py", line 136, in bootstrap self.suite.debootstrap() File "/usr/lib/python2.7/dist-packages/VMBuilder/plugins/ubuntu/dapper.py", line 269, in debootstrap run_cmd(*cmd, **kwargs) File "/usr/lib/python2.7/dist-packages/VMBuilder/util.py", line 113, in run_cmd fds = select.select([x.file for x in [mystdout, mystderr] if not x.closed], [], [])[0]

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  • Why Is Faulty Behaviour In The .NET Framework Not Fixed?

    - by Alois Kraus
    Here is the scenario: You have a Windows Form Application that calls a method via Invoke or BeginInvoke which throws exceptions. Now you want to find out where the error did occur and how the method has been called. Here is the output we do get when we call Begin/EndInvoke or simply Invoke The actual code that was executed was like this:         private void cInvoke_Click(object sender, EventArgs e)         {             InvokingFunction(CallMode.Invoke);         }            [MethodImpl(MethodImplOptions.NoInlining)]         void InvokingFunction(CallMode mode)         {             switch (mode)             {                 case CallMode.Invoke:                     this.Invoke(new MethodInvoker(GenerateError));   The faulting method is called GenerateError which does throw a NotImplementedException exception and wraps it in a NotSupportedException.           [MethodImpl(MethodImplOptions.NoInlining)]         void GenerateError()         {             F1();         }           private void F1()         {             try             {                 F2();             }             catch (Exception ex)             {                 throw new NotSupportedException("Outer Exception", ex);             }         }           private void F2()         {            throw new NotImplementedException("Inner Exception");         } It is clear that the method F2 and F1 did actually throw these exceptions but we do not see them in the call stack. If we directly call the InvokingFunction and catch and print the exception we can find out very easily how we did get into this situation. We see methods F1,F2,GenerateError and InvokingFunction directly in the stack trace and we see that actually two exceptions did occur. Here is for comparison what we get from Invoke/EndInvoke System.NotImplementedException: Inner Exception     StackTrace:    at System.Windows.Forms.Control.MarshaledInvoke(Control caller, Delegate method, Object[] args, Boolean synchronous)     at System.Windows.Forms.Control.Invoke(Delegate method, Object[] args)     at WindowsFormsApplication1.AppForm.InvokingFunction(CallMode mode)     at WindowsFormsApplication1.AppForm.cInvoke_Click(Object sender, EventArgs e)     at System.Windows.Forms.Control.OnClick(EventArgs e)     at System.Windows.Forms.Button.OnClick(EventArgs e) The exception message is kept but the stack starts running from our Invoke call and not from the faulting method F2. We have therefore no clue where this exception did occur! The stack starts running at the method MarshaledInvoke because the exception is rethrown with the throw catchedException which resets the stack trace. That is bad but things are even worse because if previously lets say 5 exceptions did occur .NET will return only the first (innermost) exception. That does mean that we do not only loose the original call stack but all other exceptions and all data contained therein as well. It is a pity that MS does know about this and simply closes this issue as not important. Programmers will play a lot more around with threads than before thanks to TPL, PLINQ that do come with .NET 4. Multithreading is hyped quit a lot in the press and everybody wants to use threads. But if the .NET Framework makes it nearly impossible to track down the easiest UI multithreading issue I have a problem with that. The problem has been reported but obviously not been solved. .NET 4 Beta 2 did not have changed that dreaded GetBaseException call in MarshaledInvoke to return only the innermost exception of the complete exception stack. It is really time to fix this. WPF on the other hand does the right thing and wraps the exceptions inside a TargetInvocationException which makes much more sense. But Not everybody uses WPF for its daily work and Windows forms applications will still be used for a long time. Below is the code to repro the issues shown and how the exceptions can be rendered in a meaningful way. The default Exception.ToString implementation generates a hard to interpret stack if several nested exceptions did occur. using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using System.Threading; using System.Globalization; using System.Runtime.CompilerServices;   namespace WindowsFormsApplication1 {     public partial class AppForm : Form     {         enum CallMode         {             Direct = 0,             BeginInvoke = 1,             Invoke = 2         };           public AppForm()         {             InitializeComponent();             Thread.CurrentThread.CurrentUICulture = CultureInfo.InvariantCulture;             Application.ThreadException += new System.Threading.ThreadExceptionEventHandler(Application_ThreadException);         }           void Application_ThreadException(object sender, System.Threading.ThreadExceptionEventArgs e)         {             cOutput.Text = PrintException(e.Exception, 0, null).ToString();         }           private void cDirectUnhandled_Click(object sender, EventArgs e)         {             InvokingFunction(CallMode.Direct);         }           private void cDirectCall_Click(object sender, EventArgs e)         {             try             {                 InvokingFunction(CallMode.Direct);             }             catch (Exception ex)             {                 cOutput.Text = PrintException(ex, 0, null).ToString();             }         }           private void cInvoke_Click(object sender, EventArgs e)         {             InvokingFunction(CallMode.Invoke);         }           private void cBeginInvokeCall_Click(object sender, EventArgs e)         {             InvokingFunction(CallMode.BeginInvoke);         }           [MethodImpl(MethodImplOptions.NoInlining)]         void InvokingFunction(CallMode mode)         {             switch (mode)             {                 case CallMode.Direct:                     GenerateError();                     break;                 case CallMode.Invoke:                     this.Invoke(new MethodInvoker(GenerateError));                     break;                 case CallMode.BeginInvoke:                     IAsyncResult res = this.BeginInvoke(new MethodInvoker(GenerateError));                     this.EndInvoke(res);                     break;             }         }           [MethodImpl(MethodImplOptions.NoInlining)]         void GenerateError()         {             F1();         }           private void F1()         {             try             {                 F2();             }             catch (Exception ex)             {                 throw new NotSupportedException("Outer Exception", ex);             }         }           private void F2()         {            throw new NotImplementedException("Inner Exception");         }           StringBuilder PrintException(Exception ex, int identLevel, StringBuilder sb)         {             StringBuilder builtStr = sb;             if( builtStr == null )                 builtStr = new StringBuilder();               if( ex == null )                 return builtStr;                 WriteLine(builtStr, String.Format("{0}: {1}", ex.GetType().FullName, ex.Message), identLevel);             WriteLine(builtStr, String.Format("StackTrace: {0}", ShortenStack(ex.StackTrace)), identLevel + 1);             builtStr.AppendLine();               return PrintException(ex.InnerException, ++identLevel, builtStr);         }               void WriteLine(StringBuilder sb, string msg, int identLevel)         {             foreach (string trimmedLine in SplitToLines(msg)                                            .Select( (line) => line.Trim()) )             {                 for (int i = 0; i < identLevel; i++)                     sb.Append('\t');                 sb.Append(trimmedLine);                 sb.AppendLine();             }         }           string ShortenStack(string stack)         {             int nonAppFrames = 0;             // Skip stack frames not part of our app but include two foreign frames and skip the rest             // If our stack frame is encountered reset counter to 0             return SplitToLines(stack)                               .Where((line) =>                               {                                   nonAppFrames = line.Contains("WindowsFormsApplication1") ? 0 : nonAppFrames + 1;                                   return nonAppFrames < 3;                               })                              .Select((line) => line)                              .Aggregate("", (current, line) => current + line + Environment.NewLine);         }           static char[] NewLines = Environment.NewLine.ToCharArray();         string[] SplitToLines(string str)         {             return str.Split(NewLines, StringSplitOptions.RemoveEmptyEntries);         }     } }

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  • Optimizing hash lookup & memory performance in Go

    - by Moishe
    As an exercise, I'm implementing HashLife in Go. In brief, HashLife works by memoizing nodes in a quadtree so that once a given node's value in the future has been calculated, it can just be looked up instead of being re-calculated. So eg. if you have a node at the 8x8 level, you remember it by its four children (each at the 2x2 level). So next time you see an 8x8 node, when you calculate the next generation, you first check if you've already seen a node with those same four children. This is extended up through all levels of the quadtree, which gives you some pretty amazing optimizations if eg. you're 10 levels above the leaves. Unsurprisingly, it looks like the perfmance crux of this is the lookup of nodes by child-node values. Currently I have a hashmap of {&upper_left_node,&upper_right_node,&lower_left_node,&lower_right_node} -> node So my lookup function is this: func FindNode(ul, ur, ll, lr *Node) *Node { var node *Node var ok bool nc := NodeChildren{ul, ur, ll, lr} node, ok = NodeMap[nc] if ok { return node } node = &Node{ul, ur, ll, lr, 0, ul.Level + 1, nil} NodeMap[nc] = node return node } What I'm trying to figure out is if the "nc := NodeChildren..." line causes a memory allocation each time the function is called. If it does, can I/should I move the declaration to the global scope and just modify the values each time this function is called? Or is there a more efficient way to do this? Any advice/feedback would be welcome. (even coding style nits; this is literally the first thing I've written in Go so I'd love any feedback)

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  • Refactoring FizzBuzz

    - by MarkPearl
    A few years ago I blogger about FizzBuzz, at the time the post was prompted by Scott Hanselman who had podcasted about how surprized he was that some programmers could not even solve the FizzBuzz problem within a reasonable period of time during a job interview. At the time I thought I would give the problem a go in F# and sure enough the solution was fairly simple – I then also did a basic solution in C# but never posted it. Since then I have learned that being able to solve a problem and how you solve the problem are two totally different things. Today I decided to give the problem a retry and see if I had learnt anything new in the last year or so. Here is how my solution looked after refactoring… Solution 1 – Cheap and Nasty public class FizzBuzzCalculator { public string NumberFormat(int number) { var numDivisibleBy3 = (number % 3) == 0; var numDivisibleBy5 = (number % 5) == 0; if (numDivisibleBy3 && numDivisibleBy5) return String.Format("{0} FizzBuz", number); else if (numDivisibleBy3) return String.Format("{0} Fizz", number); else if (numDivisibleBy5) return String.Format("{0} Buz", number); return number.ToString(); } } class Program { static void Main(string[] args) { var fizzBuzz = new FizzBuzzCalculator(); for (int i = 0; i < 100; i++) { Console.WriteLine(fizzBuzz.NumberFormat(i)); } } } My first attempt I just looked at solving the problem – it works, and could be an acceptable solution but tonight I thought I would see how far  I could refactor it… The section I decided to focus on was the mass of if..else code in the NumberFormat method. Solution 2 – Replacing If…Else with a Dictionary public class FizzBuzzCalculator { private readonly Dictionary<Tuple<bool, bool>, string> _mappings; public FizzBuzzCalculator(Dictionary<Tuple<bool, bool>, string> mappings) { _mappings = mappings; } public string NumberFormat(int number) { var numDivisibleBy3 = (number % 3) == 0; var numDivisibleBy5 = (number % 5) == 0; var mappedKey = new Tuple<bool, bool>(numDivisibleBy3, numDivisibleBy5); return String.Format("{0} {1}", number, _mappings[mappedKey]); } } class Program { static void Main(string[] args) { var mappings = new Dictionary<Tuple<bool, bool>, string> { { new Tuple<bool, bool>(true, true), "- FizzBuzz"}, { new Tuple<bool, bool>(true, false), "- Fizz"}, { new Tuple<bool, bool>(false, true), "- Buzz"}, { new Tuple<bool, bool>(false, false), ""} }; var fizzBuzz = new FizzBuzzCalculator(mappings); for (int i = 0; i < 100; i++) { Console.WriteLine(fizzBuzz.NumberFormat(i)); } Console.ReadLine(); } } In my second attempt I looked at removing the if else in the NumberFormat method. A dictionary proved to be useful for this – I added a constructor to the class and injected the dictionary mapping. One could argue that this is totally overkill, but if I was going to use this code in a large system an approach like this makes it easy to put this data in a configuration file, which would up its OC (Open for extensibility, closed for modification principle). I could of course take the OC principle even further – the check for divisibility by 3 and 5 is tightly coupled to this class. If I wanted to make it 4 instead of 3, I would need to adjust this class. This introduces my third refactoring. Solution 3 – Introducing Delegates and Injecting them into the class public delegate bool FizzBuzzComparison(int number); public class FizzBuzzCalculator { private readonly Dictionary<Tuple<bool, bool>, string> _mappings; private readonly FizzBuzzComparison _comparison1; private readonly FizzBuzzComparison _comparison2; public FizzBuzzCalculator(Dictionary<Tuple<bool, bool>, string> mappings, FizzBuzzComparison comparison1, FizzBuzzComparison comparison2) { _mappings = mappings; _comparison1 = comparison1; _comparison2 = comparison2; } public string NumberFormat(int number) { var mappedKey = new Tuple<bool, bool>(_comparison1(number), _comparison2(number)); return String.Format("{0} {1}", number, _mappings[mappedKey]); } } class Program { private static bool DivisibleByNum(int number, int divisor) { return number % divisor == 0; } public static bool Divisibleby3(int number) { return number % 3 == 0; } public static bool Divisibleby5(int number) { return number % 5 == 0; } static void Main(string[] args) { var mappings = new Dictionary<Tuple<bool, bool>, string> { { new Tuple<bool, bool>(true, true), "- FizzBuzz"}, { new Tuple<bool, bool>(true, false), "- Fizz"}, { new Tuple<bool, bool>(false, true), "- Buzz"}, { new Tuple<bool, bool>(false, false), ""} }; var fizzBuzz = new FizzBuzzCalculator(mappings, Divisibleby3, Divisibleby5); for (int i = 0; i < 100; i++) { Console.WriteLine(fizzBuzz.NumberFormat(i)); } Console.ReadLine(); } } I have taken this one step further and introduced delegates that are injected into the FizzBuzz Calculator class, from an OC principle perspective it has probably made it more compliant than the previous Solution 2, but there seems to be a lot of noise. Anonymous Delegates increase the readability level, which is what I have done in Solution 4. Solution 4 – Anon Delegates public delegate bool FizzBuzzComparison(int number); public class FizzBuzzCalculator { private readonly Dictionary<Tuple<bool, bool>, string> _mappings; private readonly FizzBuzzComparison _comparison1; private readonly FizzBuzzComparison _comparison2; public FizzBuzzCalculator(Dictionary<Tuple<bool, bool>, string> mappings, FizzBuzzComparison comparison1, FizzBuzzComparison comparison2) { _mappings = mappings; _comparison1 = comparison1; _comparison2 = comparison2; } public string NumberFormat(int number) { var mappedKey = new Tuple<bool, bool>(_comparison1(number), _comparison2(number)); return String.Format("{0} {1}", number, _mappings[mappedKey]); } } class Program { static void Main(string[] args) { var mappings = new Dictionary<Tuple<bool, bool>, string> { { new Tuple<bool, bool>(true, true), "- FizzBuzz"}, { new Tuple<bool, bool>(true, false), "- Fizz"}, { new Tuple<bool, bool>(false, true), "- Buzz"}, { new Tuple<bool, bool>(false, false), ""} }; var fizzBuzz = new FizzBuzzCalculator(mappings, (n) => n % 3 == 0, (n) => n % 5 == 0); for (int i = 0; i < 100; i++) { Console.WriteLine(fizzBuzz.NumberFormat(i)); } Console.ReadLine(); } }   Using the anonymous delegates I think the noise level has now been reduced. This is where I am going to end this post, I have gone through 4 iterations of the code from the initial solution using If..Else to delegates and dictionaries. I think each approach would have it’s pro’s and con’s and depending on the intention of where the code would be used would be a large determining factor. If you can think of an alternative way to do FizzBuzz, add a comment!

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  • How to properly diagram lambda expressions or traversals through them in Architecture Explorer?

    - by MainMa
    I'm exploring a piece of code in Architecture Explorer in Visual Studio 2010 to study the relations between methods. I noticed a strange behavior. Take the following source code. It generates a hello message based on a template and a template engine, the template engine being a method (a sort of strategy pattern simplified at a maximum for demo purposes). public string GenerateHelloMessage(string personName) { return this.ApplyTemplate( this.DefaultTemplateEngine, this.GenerateLocalizedHelloTemplate(), personName); } private string GenerateLocalizedHelloTemplate() { return "Hello {0}!"; } public string ApplyTemplate( Func<string, string, string> templateEngine, string template, string personName) { return templateEngine(template, personName); } public string DefaultTemplateEngine(string template, string personName) { return string.Format(template, personName); } The graph generated from this code is this one: Change the first method from this: public string GenerateHelloMessage(string personName) { return this.ApplyTemplate( this.DefaultTemplateEngine, this.GenerateLocalizedHelloTemplate(), personName); } to this: public string GenerateHelloMessage(string personName) { return this.ApplyTemplate( (a, b) => this.DefaultTemplateEngine(a, b), this.GenerateLocalizedHelloTemplate(), personName); } and the graph becomes: While semantically identical, those two versions of code produce different dependency graphs, and Architecture Explorer shows no trace of the lambda expression (while Visual Studio's code coverage, for example, shows them, as well as Code analysis seems to be able to understand that the link exists). How would it be possible, without changing the source code, to: Either force Architecture Explorer to display everything, including lambda expressions, Or make it traverse lambda expressions while drawing a dependency through them (so in this case, drawing the dependency from GenerateHelloMessage to DefaultTemplateEngine in the second example)?

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