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  • Efficiently generate a 16-character, alphanumeric string

    - by ensnare
    I'm looking for a very quick way to generate an alphanumeric unique id for a primary key in a table. Would something like this work? def genKey(): hash = hashlib.md5(RANDOM_NUMBER).digest().encode("base64") alnum_hash = re.sub(r'[^a-zA-Z0-9]', "", hash) return alnum_hash[:16] What would be a good way to generate random numbers? If I base it on microtime, I have to account for the possibility of several calls of genKey() at the same time from different instances. Or is there a better way to do all this? Thanks.

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  • How to set a __str__ method for all ctype Structure classes?

    - by Reuben Thomas
    [Since asking this question, I've found: http://www.cs.unc.edu/~gb/blog/2007/02/11/ctypes-tricks/ which gives a good answer.] I just wrote a __str__ method for a ctype-generated Structure class 'foo' thus: def foo_to_str(self): s = [] for i in foo._fields_: s.append('{}: {}'.format(i[0], foo.\_\_getattribute__(self, i[0]))) return '\n'.join(s) foo.\_\_str__ = foo_to_str But this is a fairly natural way to produce a __str__ method for any Structure class. How can I add this method directly to the Structure class, so that all Structure classes generated by ctypes get it? (I am using the h2xml and xml2py scripts to auto-generate ctypes code, and this offers no obvious way to change the names of the classes output, so simply subclassing Structure, Union &c. and adding my __str__ method there would involve post-processing the output of xml2py.)

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  • How to save and load an array of complex numbers using numpy.savetxt?

    - by ptomato
    I want to use numpy.savetxt() to save an array of complex numbers to a text file. Problems: If you save the complex array with the default format string, the imaginary part is discarded. If you use fmt='%s', then numpy.loadtxt() can't load it unless you specify dtype=complex, converters={0: lambda s: complex(s)}. Even then, if there are NaN's in the array, loading still fails. It looks like someone has inquired about this multiple times on the Numpy mailing list and even filed a bug, but has not gotten a response. Before I put something together myself, is there a canonical way to do this?

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  • Iterate with binary structure over numpy array to get cell sums

    - by Curlew
    In the package scipy there is the function to define a binary structure (such as a taxicab (2,1) or a chessboard (2,2)). import numpy from scipy import ndimage a = numpy.zeros((6,6), dtype=numpy.int) a[1:5, 1:5] = 1;a[3,3] = 0 ; a[2,2] = 2 s = ndimage.generate_binary_structure(2,2) # Binary structure #.... Calculate Sum of result_array = numpy.zeros_like(a) What i want is to iterate over all cells of this array with the given structure s. Then i want to append a function to the current cell value indexed in a empty array (example function sum), which uses the values of all cells in the binary structure. For example: array([[0, 0, 0, 0, 0, 0], [0, 1, 1, 1, 1, 0], [0, 1, 2, 1, 1, 0], [0, 1, 1, 0, 1, 0], [0, 1, 1, 1, 1, 0], [0, 0, 0, 0, 0, 0]]) # The array a. The value in cell 1,2 is currently one. Given the structure s and an example function such as sum the value in the resulting array (result_array) becomes 7 (or 6 if the current cell value is excluded). Someone got an idea?

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  • Distance between numpy arrays, columnwise

    - by Jaapsneep
    I have 2 arrays in 2D, where the column vectors are feature vectors. One array is of size F x A, the other of F x B, where A << B. As an example, for A = 2 and F = 3 (B can be anything): arr1 = np.array( [[1, 4], [2, 5], [3, 6]] ) arr2 = np.array( [[1, 4, 7, 10, ..], [2, 5, 8, 11, ..], [3, 6, 9, 12, ..]] ) I want to calculate the distance between arr1 and a fragment of arr2 that is of equal size (in this case, 3x2), for each possible fragment of arr2. The column vectors are independent of each other, so I believe I should calculate the distance between each column vector in arr1 and a collection of column vectors ranging from i to i + A from arr2 and take the sum of these distances (not sure though). Does numpy offer an efficient way of doing this, or will I have to take slices from the second array and, using another loop, calculate the distance between each column vector in arr1 and the corresponding column vector in the slice?

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  • any faster alternative??

    - by kaushik
    cost=0 for i in range(12): cost=cost+math.pow(float(float(q[i])-float(w[i])),2) cost=(math.sqrt(cost)) Any faster alternative to this? i am need to improve my entire code so trying to improve each statements performance. thanking u

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  • SQLAlchemy Expression Language problem

    - by Torkel
    I'm trying to convert this to something sqlalchemy expression language compatible, I don't know if it's possible out of box and are hoping someone more experienced can help me along. The backend is PostgreSQL and if I can't make it as an expression I'll create a string instead. SELECT DISTINCT date_trunc('month', x.x) as date, COALESCE(b.res1, 0) AS res1, COALESCE(b.res2, 0) AS res2 FROM generate_series( date_trunc('year', now() - interval '1 years'), date_trunc('year', now() + interval '1 years'), interval '1 months' ) AS x LEFT OUTER JOIN( SELECT date_trunc('month', access_datetime) AS when, count(NULLIF(resource_id != 1, TRUE)) AS res1, count(NULLIF(resource_id != 2, TRUE)) AS res2 FROM tracking_entries GROUP BY date_trunc('month', access_datetime) ) AS b ON (date_trunc('month', x.x) = b.when) First of all I got a class TrackingEntry mapped to tracking_entries, the select statement within the outer joined can be converted to something like (pseudocode):: from sqlalchemy.sql import func, select from datetime import datetime, timedelta stmt = select([ func.date_trunc('month', TrackingEntry.resource_id).label('when'), func.count(func.nullif(TrackingEntry.resource_id != 1, True)).label('res1'), func.count(func.nullif(TrackingEntry.resource_id != 2, True)).label('res2') ], group_by=[func.date_trunc('month', TrackingEntry.access_datetime), ]) Considering the outer select statement I have no idea how to build it, my guess is something like: outer = select([ func.distinct(func.date_trunc('month', ?)).label('date'), func.coalesce(?.res1, 0).label('res1'), func.coalesce(?.res2, 0).label('res2') ], from_obj=[ func.generate_series( datetime.now(), datetime.now() + timedelta(days=365), timedelta(days=1) ).label(x) ]) Then I suppose I have to link those statements together without using foreign keys: outer.outerjoin(stmt???).??(func.date_trunc('month', ?.?), ?.when) Anyone got any suggestions or even better a solution?

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  • Accessing CSR extension stack in M2Crypto

    - by Charles Duffy
    Howdy! I have a certificate signing request with an extension stack added. When building a certificate based on this request, I would like to be able to access that stack to use in creating the final certificate. However, while M2Crypto.X509.X509 has a number of helpers for accessing extensions (get_ext, get_ext_at and the like), M2Crypto.X509.Request appears to provide only a member for adding extensions, but no way to inspect the extensions already associated with a given object. Am I missing something here?

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  • SQLAlchemy: a better way for update with declarative?

    - by hadrien
    I am a SQLAlchemy noob. Let's say I have an user table in declarative mode: class User(Base): __tablename__ = 'user' id = Column(u'id', Integer(), primary_key=True) name = Column(u'name', String(50)) When I know user's id without object loaded into session, I update such user like this: ex = update(User.__table__).where(User.id==123).values(name=u"Bob Marley") Session.execute(ex) I dislike using User.__table__, should I stop worrying with that? Is there a better way to do this? Thanx!

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  • SQLAlchemy: who is in charge of the "session"? ( and how to unit-test with sessions )

    - by Nick Perkins
    I need some guidance on how to use session objects with SQLAlchemy, and how to organize Unit Tests of my mapped objects. What I would like to able to do is something like this: thing = BigThing() # mapped object child = thing.new_child() # create and return a related object thing.save() # will also save the child object In order to achieve this, I was thinking of having the BigThing actually add itself ( and it's children ) to the database -- but maybe this not a good idea? One reason to add objects as soon as possible is Automatic id values that are assigned by the database -- the sooner they are available, the fewer problems there are ( right? ) What is the best way to manage session objects? Who is in charge of the session? Should it be created only when required? or saved for a long time? What about Unit Tests for my mapped objects?...how should the session be handled? Is it ever OK to have mapped objects just automatically add themselves to a database? or is that going to lead to trouble?

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  • any faster alternative??

    - by kaushik
    I have to read a file from a particular line number and i know the line number say "n": i have been thinking of two choice: 1)for i in range(n) fname.readline() k=readline() print k 2)i=0 for line in fname: dictionary[i]=line i=i+1 but i want to know faster alternative as i might have to perform this on different files 20000 times. is there is any other better alternatives?? thanking u

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  • Facebook Scrumptious sample app won't build

    - by Chase Roberts
    I did exactly what they do in the video. However, when I get to the scrumptious app and try to build/run it, mine fails. It says: "Parse Issue. Expected a type." Here are the two lines that it thinks are broken (located in the ACAccountStore.h): // Returns the account type object matching the account type identifier. See // ACAccountType.h for well known account type identifiers - (ACAccountType *)accountTypeWithAccountTypeIdentifier:(NSString *)typeIdentifier; // Returns the accounts matching a given account type. - (NSArray *)accountsWithAccountType:(ACAccountType *)accountType; Here is a link to the tutorial. I only didn't even make it two min in before I hit this wall. http://developers.facebook.com/docs/getting-started/facebook-sdk-for-ios/3.1/ I am running Xcode v4.4.1.

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  • Smart Client App: How to give Different Settings for Different Users

    - by Daniel
    Hi! I have a smart client application being deployed with a CickOnce webpage. here's the current scenario. User runs the application, and the application shows a login form. User enters ID/Password in the login form, and the application sends that information to the server. The server authenticates the user and sends configuration and data to the application. Different users have different configuration and data for their application. I was concerned that anyone can download the application from the webpage if they know the URL. So I'm trying to change the authentication scheme, so that users can login at the webpage to download the application. I want to send the authentication info from the webpage(Program running at the server) to the smart client app, so that application can download the configuration information from the server, without prompting users to make a login again. How can the webpage send the ID/Passoword to the application securely?

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  • pyramid traversal resource url no attribute __name__

    - by Santana
    So I have: resources.py: def _add(obj, name, parent): obj.__name__ = name obj.__parent__ = parent return obj class Root(object): __parent__ = __name__ = None def __init__(self, request): super(Root, self).__init__() self.request = request self.collection = request.db.post def __getitem__(self, key): if u'profile' in key: return Profile(self.request) class Profile(dict): def __init__(self, request): super(Profile, self).__init__() self.__name__ = u'profile' self.__parent__ = Root self.collection = request.db.posts def __getitem__(self, name): post = Dummy(self.collection.find_one(dict(username=name))) return _add(post, name, self) and I'm using MongoDB and pyramid_mongodb views.py: @view_config(context = Profile, renderer = 'templates/mytemplate.pt') def test_view(request): return {} and in mytemplate.pt: <p tal:repeat='item request.context'> ${item} </p> I can echo what's in the database (I'm using mongodb), but when I provided a URL for each item using resource_url() <p tal:repeat='item request.context'> <a href='${request.resource_url(item)}'>${item}</a> </p> I got an error: 'dict' object has no attribute '__name__', can someone help me?

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  • How to convert string "0671" or "0x45" into integer form with 0 and 0x in the beginning.

    - by Harshit Sharma
    I wanted to make my own encryption algorithm and decryption algorithm , encryption algorithm works fine and converts ascii value of the characters into alternate hexadecimal and octal representations. But when I tried decryption, problem occured as it return int('0671') = 671, as 0671 is string type in the following code. Is there a method to convert "ox56" into integer form?????? NOTE: Following string is alternate octal and hexa of ascii value of char. ///////////////DECRYPTION/////// l="01630x7401620x6901560x67" f=len(l) k=0 d=0 x=[] for i in range(0,f,4): g=l[i:i+4] print g k=k+1 if(k%2==0): p=g print p else: p=int(g) print p

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  • Adding a red5 app in a multiuser website

    - by Zakaria
    hi everybody, I have an mvc php website where users can publish their public information: http://www.example.com/foobar/profile. Beside this project, based on some red5 samples, I have an application (done with Flex) that sends audio: rtmp://server/sendAudio (very basic but works). I want to create for each subscribed on my website an admin part where can send an audio stream: http://admin.example.com/foobar. And, when someone goes on their public profile, they can listen to the streamed audio: http://www.example.com/foobar/profile). How can I use my red5/flash app dynamically with my php website so that my users can broadcast their proper canal? Do you have some experience to share ? Thank you, Regards.

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  • Right way to return proxy model instance from a base model instance in Django ?

    - by sotangochips
    Say I have models: class Animal(models.Model): type = models.CharField(max_length=255) class Dog(Animal): def make_sound(self): print "Woof!" class Meta: proxy = True class Cat(Animal): def make_sound(self): print "Meow!" class Meta: proxy = True Let's say I want to do: animals = Animal.objects.all() for animal in animals: animal.make_sound() I want to get back a series of Woofs and Meows. Clearly, I could just define a make_sound in the original model that forks based on animal_type, but then every time I add a new animal type (imagine they're in different apps), I'd have to go in and edit that make_sound function. I'd rather just define proxy models and have them define the behavior themselves. From what I can tell, there's no way of returning mixed Cat or Dog instances, but I figured maybe I could define a "get_proxy_model" method on the main class that returns a cat or a dog model. Surely you could do this, and pass something like the primary key and then just do Cat.objects.get(pk = passed_in_primary_key). But that'd mean doing an extra query for data you already have which seems redundant. Is there any way to turn an animal into a cat or a dog instance in an efficient way? What's the right way to do what I want to achieve?

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  • Assigning a material in Blender with a script

    - by Narcolapser
    Question: How do you assign a material with a script to an object in blender? Info: I have this script to import a proprietary model type of mine that is basically a star map with object consisting of a single vertex. in order to make them look like stars and be visible they are all going to have a halo material assigned to them. I'm figuring out how to make this material and give it the values just fine, but I can't seem to get it to assign. I tried the most obvious thing which was: objectName.setMaterial(materialName) but that did nothing. and when i would take an object that had a material and call the getMaterial function on it, it would return nothing. there is something I'm missing here, can some one shed some light on it? Thanks. ~TA

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  • Validating key/certificate pairs with M2Crypto when a certificate chain is needed

    - by Charles Duffy
    M2Crypto.X509.X509 objects have a verify(pkey) method, which provide a means of testing that a given certificate does in fact sign a specified key. This is a good and useful thing -- except that sometimes the certificate I want to verify in this way is invalid without the use of an intermediate certificate, which this API does not appear to allow a way to specify. Is there an alternate means of validating a certificate / private key pair which will work even when the certificate is unable to stand alone?

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  • Images to video - converting to IplImage makes video blue

    - by user891908
    I want to create a video from images using opencv. The strange problem is that if i will write image (bmp) to disk and then load (cv.LoadImage) it it renders fine, but when i try to load image from StringIO and convert it to IplImage, it turns video to blue. Heres the code: import StringIO output = StringIO.StringIO() FOREGROUND = (0, 0, 0) TEXT = 'MY TEXT' font_path = 'arial.ttf' font = ImageFont.truetype(font_path, 18, encoding='unic') text = TEXT.decode('utf-8') (width, height) = font.getsize(text) # Create with background with place for text w,h=(600,600) contentimage=Image.open('0.jpg') background=Image.open('background.bmp') x, y = contentimage.size # put content onto background background.paste(contentimage,(((w-x)/2),0)) draw = ImageDraw.Draw(background) draw.text((0,0), text, font=font, fill=FOREGROUND) pi = background pi.save(output, "bmp") #pi.show() #shows image in full color output.seek(0) pi= Image.open(output) print pi, pi.format, "%dx%d" % pi.size, pi.mode cv_im = cv.CreateImageHeader(pi.size, cv.IPL_DEPTH_8U, 3) cv.SetData(cv_im, pi.tostring()) print pi.size, cv.GetSize(cv_im) w = cv.CreateVideoWriter("2.avi", cv.CV_FOURCC('M','J','P','G'), 1,(cv.GetSize(cv_im)[0],cv.GetSize(cv_im)[1]), is_color=1) for i in range(1,5): cv.WriteFrame(w, cv_im) del w

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  • In plain English, what are Django generic views?

    - by allyourcode
    The first two paragraphs of this page explain that generic views are supposed to make my life easier, less monotonous, and make me more attractive to women (I made up that last one): http://docs.djangoproject.com/en/dev/topics/generic-views/#topics-generic-views I'm all for improving my life, but what do generic views actually do? It seems like lots of buzzwords are being thrown around, which confuse more than they explain. Are generic views similar to scaffolding in Ruby on Rails? The last bullet point in the intro seems to indicate this. Is that an accurate statement?

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  • class inheretence of a attribute which is itself a class

    - by alex
    i have a class which inherets a attribute from a super-class. this attribute is a class itself. class classA(superClass): def func(self,x): if self.attributeB is None: do somthing and in the other class i have class superClass: self.attributB = classB() i get the error AttributeError: class classA has no attribute 'attributeB' when i access the attribute like i showed but if on command line i can see it works, x = classA() x.attributeB is None True so the test works. whats going on in the above code?

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