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  • Finding a Eulerian Tour

    - by user590903
    I am trying to solve a problem on Udacity described as follows: # Find Eulerian Tour # # Write a function that takes in a graph # represented as a list of tuples # and return a list of nodes that # you would follow on an Eulerian Tour # # For example, if the input graph was # [(1, 2), (2, 3), (3, 1)] # A possible Eulerian tour would be [1, 2, 3, 1] I came up with the following solution, which, while not as elegant as some of the recursive algorithms, does seem to work within my test case. def find_eulerian_tour(graph): tour = [] start_vertex = graph[0][0] tour.append(start_vertex) while len(graph) > 0: current_vertex = tour[len(tour) - 1] for edge in graph: if current_vertex in edge: if edge[0] == current_vertex: current_vertex = edge[1] else: current_vertex = edge[0] graph.remove(edge) tour.append(current_vertex) break return tour graph = [(1, 2), (2, 3), (3, 1)] print find_eulerian_tour(graph) >> [1, 2, 3, 1] However, when submitting this, I get rejected by the grader. I am doing something wrong? I can't see any errors.

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  • Putting a thread to sleep until event X occurs

    - by tipu
    I'm writing to many files in a threaded app and I'm creating one handler per file. I have HandlerFactory class that manages the distribution of these handlers. What I'd like to do is that thread A requests and gets foo.txt's file handle from the HandlerFactory class thread B requests foo.txt's file handler handler class recognizes that this file handle has been checked out handler class puts thread A to sleep thread B closes file handle using a wrapper method from HandlerFactory HandlerFactory notifies sleeping threads thread B wakes and successfully gets foo.txt's file handle This is what I have so far, def get_handler(self, file_path, type): self.lock.acquire() if file_path not in self.handlers: self.handlers[file_path] = open(file_path, type) elif not self.handlers[file_path].closed: time.sleep(1) self.lock.release() return self.handlers[file_path][type] I believe this covers the sleeping and handler retrieval successfully, but I am unsure how to wake up all threads, or even better wake up a specific thread.

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  • Problems with 'while' loop and 'for' loop when reading through file

    - by David Beckham
    I wasted plenty of hours trying to figure out the problem but no luck. Tried asking the TA at my school, but he was useless. I am a beginner and I know there are a lot of mistakes in it, so it would be great if I can get some detail explanation as well. Anyways, basically what I am trying to do with the following function is: Use while loop to check and see if random_string is in TEXT, if not return NoneType if yes, then use a for loop to read lines from that TEXT and put it in list, l1. then, write an if statement to see if random_string is in l1. if it is, then do some calculations. else read the next line Finally, return the calculations as a whole. TEXT = open('randomfile.txt') def random (TEXT, random_string): while random_string in TEXT: for lines in TEXT: l1=TEXT.readline().rsplit() if random_string in l1: ''' do some calculations ''' else: TEXT.readline() #read next line??? return #calculations return None

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  • One-line expression to map dictionary to another

    - by No Such IP
    I have dictionary like d = {'user_id':1, 'user':'user1', 'group_id':3, 'group_name':'ordinary users'} and "mapping" dictionary like: m = {'user_id':'uid', 'group_id':'gid', 'group_name':'group'} All i want to "replace" keys in first dictionary with keys from second (e.g. replace 'user_id' with 'uid', etc.) I know that keys are immutable and i know how to do it with 'if/else' statement. But maybe there is way to do it in one line expression?

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  • Web and stand-alone apps development tendency

    - by Narek
    There is a strong tendency of making web apps and even seems that very soon a lot of features will be available online so that for every day use people will have all necessary software free online and they will not need to install any software locally. Only specific (professional) tools that usually people don’t use at home will not be available as a web app. So my question, how do you imagine selling software that was necessary for everyday use and was not free (seems they can't make money any more by selling their product – no need of those products). And what disadvantages have web apps, that is to say, what is bad to use software online compared with having the same software locally (please list)? Please do not consider this question not connected with programming, as I really would like to have a little statistics from professional programmers who are aware from nowday’s tendency of software and programming. Thanks.

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  • Django model class and custom property

    - by dArignac
    Howdy - today a weird problem occured to me: I have a modle class in Django and added a custom property to it that shall not be saved into the database and therefore is not represent in the models structure: class Category(models.Model): groups = models.ManyToManyField(Group) title = defaultdict() Now, when I'm within the shell or writing a test and I do the following: c1 = Category.objects.create() c1.title['de'] = 'german title' print c1.title['de'] # prints "german title" c2 = Category.objects.create() print c2.title['de'] # prints "german title" <-- WTF? It seems that 'title' is kind of global. If I change title to a simple string it works as expected, so it has to do something with the dict? I also tried setting title as a property: title = property(_title) But that did not work, too. So, how can I solve this? Thank you in advance! enter code here

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  • How i can do image CROP in OpenCV

    - by Nolik
    How i can do image crop such in PIL in OpenCV. Working example on PIL im = Image.open('0.png').convert('L') im = im.crop((1, 1, 98, 33)) im.save('_0.png') But how i can do it on OpenCV? I wanted to do so im = cv.imread('0.png', cv.CV_LOAD_IMAGE_GRAYSCALE) (thresh, im_bw) = cv.threshold(im, 128, 255, cv.THRESH_OTSU) im = cv.getRectSubPix(im_bw, (98, 33), (1, 1)) cv.imshow('Img', im) cv.waitKey(0) But it doesnt work. I think, i wrong use getRectSubPix. If it true, please explain how i can correctly use this function. Thanks.

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  • finding a solution to a giving maze txt.file

    - by alberto
    how can i fix this program, the problem is when it print out the coordinate it give me a 7 for the start and finish, i would appreciated you help, thanks start = (len(data)) finish = (len(data)) pos= [] for i in range(len(pos)): for j in range(len(pos[i])): if pos[i][j] == "S": start=(i,j) elif pos[i][j] == "F": finish=(i,j) print "S found in",start, print "\nF found in",finish,"\n"

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  • Best practice: How to persist simple data without a database in django?

    - by Infinity
    I'm building a website that doesn't require a database because a REST API "is the database". (Except you don't want to be putting site-specific things in there, since the API is used by mostly mobile clients) However there's a few things that normally would be put in a database, for example the "jobs" page. You have master list view, and the detail views for each job, and it should be easy to add new job entries. (not necessarily via a CMS, but that would be awesome) e.g. example.com/careers/ and example.com/careers/77/ I could just hardcode this stuff in templates, but that's no DRY- you have to update the master template and the detail template every time. What do you guys think? Maybe a YAML file? Or any better ideas? Thx

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  • problem with list return type??

    - by kaushik
    my list has value such as m=[['na','1','2']['ka','31','45']['ra','3','5'] d=0 r=2 t=m[d][r] print t # this is givin number i.e 2 Now when I use this value u=[] u=m[t] I am getting an err msg saying type error list does take str values... i want to use like this how can i convert that t into a integer?? please suggest.. thanks..

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  • What is considered bleeding edge in programming these days?

    - by iestyn
    What is "bleeding edge" these days? has it all been done before us, and we are just discovering new ways of implementing mathematical constructs within programming? Functional Programming seems to be making inroads in all areas, but is this just marketing to create interest in a programming arena where it appears that the state of the art has climaxed too soon. have the sales men got hold of the script, and selling ideas that can be sold, dumbing down the future? I see very old ideas making their way into the market place....what are the truly new things that should be considered fresh and new in 2010 onwards, and not some 1960-1980 idea being refocused.

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  • How to access the calling source line from interactive shell

    - by TJD
    I want to make a function that can determine the source code of how it was called. I'm aware of how to do this generally with the inspect module. For example, this question, works well and provides my desired output in the lines variable as shown below: def hello(x): frame,filename,line_number,function_name,lines,index=\ inspect.getouterframes(inspect.currentframe())[1] print(frame,filename,line_number,function_name,lines,index) The problem is that this solution doesn't work in an interactive command line session. For example, from a command line, the result looks like: >>> y = hello(7) (<frame object at 0x01ECA9E8>, '<stdin>', 1, '<module>', None, None) The problem is that the source file is '<stdin>', so the lines variable is None. How can I access the calling line to find the result containing the string y = hello(7) during an interactive session?

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  • Yet another list comprehension question

    - by relima
    I had this: if Setting["Language"] == "en": f.m_radioBox3.SetSelection(0) elif Setting["Language"] == "pt": f.m_radioBox3.SetSelection(1) elif Setting["Language"] == "fr": f.m_radioBox3.SetSelection(2) elif Setting["Language"] == "es": f.m_radioBox3.SetSelection(3) Then I did this: Linguas = ["en","pt","fr","es"] a = 0 for i in Linguas: if i == Setting["Language"]: f.m_radioBox3.SetSelection(a) a += 1 Is it possible to further simplify this and make it into a one-liner?

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  • Appengine backreferences - need composite index?

    - by davezor
    I have a query that is very recently starting to throw: "The built-in indices are not efficient enough for this query and your data. Please add a composite index for this query." I checked the line on which this exception is being thrown, and the problem query is this one: count = self.vote_set.filter("direction =", 1).count() This is literally a one-filter operation using appengine's built-in backreferences. I have no idea how to optimize this query...anyone have any suggestions? I tried to add this index: - kind: Vote properties: - name: direction direction: desc - kind: Vote properties: - name: direction And I got a message (obviously) saying this was an unnecessary index. Thanks for your help in advance.

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  • Building a user subscription application

    - by Tristan O'Neil
    Hello, I'm trying to come up with the best way to handle user subscription and management for our magazine website. What I want to happen is a user purchases a subscription and they are granted online access of a certain membership role for a certain amount of time depending on how many years they subscribed for. I would also like the system to be able to send out emails when a subscription is almost up. I've seen some third party projects to help accomplish this but I'd prefer to write this from scratch as I want total control over how it works. Any suggestions would be helpful. The main thing I can't figure out is how to have an expiring membership. You must keep track of when the user signed up and how long until they should expire.

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  • How to pickle and unpickle objects with self-references and from a class with slots?

    - by EOL
    Is it possible to pickle an object from a class with slots, when this object references itself through one of its attributes? Here is a simple example: import weakref import pickle class my_class(object): __slots__ = ('an_int', 'ref_to_self', '__weakref__') def __init__(self): self.an_int = 42 self.ref_to_self = weakref.WeakKeyDictionary({self: 1}) # __getstate__ and __setstate__ not defined: how should this be done? if __name__ == '__main__': obj = my_class() # How to make the following work? obj_pickled = pickle.dumps(obj) obj_unpickled = pickle.loads(obj_pickled) # Self-references should be kept: print "OK?", obj_unpickled == obj_unpickled.ref_to_self.keys()[0]

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  • Django naturaltime Localization error

    - by Edwin Lunando
    My language ID is 'id'. I used localized humanize library for my Django template tags and use the naturaltime, but the translation is partially wrong. The now translated to sekarang is right. second to detik. minute to menit, but when it comes to date, week, or months, the word is not translated to my language. It keeps printing date, week, and months. Here are my Django configuration TIME_ZONE = 'Asia/Jakarta' LANGUAGE_CODE = 'id' SITE_ID = 1 USE_I18N = True USE_L10N = True USE_TZ = True Here how I used the naturaltime template tags. <time class="discussion__info__item">{{ object.created|naturaltime }}</time> Do I forgot something? Thank you.

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  • Changing direction of rotation Pygame

    - by czl
    How would you change the direction of a rotating image/rect in Pygame? Applying positive and negative degree values works but it seems to only be able to rotate one direction throughout my window. Is there a way to ensure a change in direction of rotation? Perhaps change up rotation of a spinning image every 5 seconds, or if able to change the direction of the spin when hitting a X or Y axis. I've added some code below. It seems like switching movement directions is easy with rect.move_ip as long as I specify a speed and have location clause, it does what I want. Unfortunately rotation is't like that. Here I'l adding angles to make sure it spins, but no matter what I try, I'm unable to negate the rotation. def rotate_image(self): #rotate image orig_rect = self.image.get_rect() rot_image = pygame.transform.rotate(self.image, self.angle) rot_rect = orig_rect.copy() rot_rect.center = rot_image.get_rect().center rot_image = rot_image.subsurface(rot_rect).copy() return rot_image def render(self): self.screen.fill(self.bg_color) self.rect.move_ip(0,5) #Y axis movement at 5 px per frame self.angle += 5 #add 5 anglewhen the rect has not hit one of the window self.angle %= 360 if self.rect.left < 0 or self.rect.right > self.width: self.speed[0] = -self.speed[0] self.angle = -self.angle #tried to invert the angle self.angle -= 5 #trying to negate the angle rotation self.angle %= 360 self.screen.blit(self.rotate_image(),self.rect) pygame.display.flip() I would really like to know how to invert rotation of a image. You may provide your own examples.

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  • Decorator that can take both init args and call args?

    - by digitala
    Is it possible to create a decorator which can be __init__'d with a set of arguments, then later have methods called with other arguments? For instance: from foo import MyDecorator bar = MyDecorator(debug=True) @bar.myfunc(a=100) def spam(): pass @bar.myotherfunc(x=False) def eggs(): pass If this is possible, can you provide a working example?

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