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• Save PyML.classifiers.multi.OneAgainstRest(SVM()) object?

  - by Michael Aaron Safyan

  I'm using PYML to construct a multiclass linear support vector machine (SVM). After training the SVM, I would like to be able to save the classifier, so that on subsequent runs I can use the classifier right away without retraining. Unfortunately, the .save() function is not implemented for that classifier, and attempting to pickle it (both with standard pickle and cPickle) yield the following error message: pickle.PicklingError: Can't pickle : it's not found as __builtin__.PySwigObject Does anyone know of a way around this or of an alternative library without this problem? Thanks. Edit/Update I am now training and attempting to save the classifier with the following code: mc = multi.OneAgainstRest(SVM()); mc.train(dataset_pyml,saveSpace=False); for i, classifier in enumerate(mc.classifiers): filename=os.path.join(prefix,labels[i]+".svm"); classifier.save(filename); Notice that I am now saving with the PyML save mechanism rather than with pickling, and that I have passed "saveSpace=False" to the training function. However, I am still gettting an error: ValueError: in order to save a dataset you need to train as: s.train(data, saveSpace = False) However, I am passing saveSpace=False... so, how do I save the classifier(s)? P.S. The project I am using this in is pyimgattr, in case you would like a complete testable example... the program is run with "./pyimgattr.py train"... that will get you this error. Also, a note on version information: [michaelsafyan@codemage /Volumes/Storage/classes/cse559/pyimgattr]$ python Python 2.6.1 (r261:67515, Feb 11 2010, 00:51:29) [GCC 4.2.1 (Apple Inc. build 5646)] on darwin Type "help", "copyright", "credits" or "license" for more information. import PyML print PyML.__version__ 0.7.0

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• what is the point of heterogenous arrays?

  - by aharon

  I know that more-dynamic-than-Java languages, like Python and Ruby, often allow you to place objects of mixed types in arrays, like so: ["hello", 120, ["world"]] What I don't understand is why you would ever use a feature like this. If I want to store heterogenous data in Java, I'll usually create an object for it. For example, say a User has int ID and String name. While I see that in Python/Ruby/PHP you could do something like this: [["John Smith", 000], ["Smith John", 001], ...] this seems a bit less safe/OO than creating a class User with attributes ID and name and then having your array: [<User: name="John Smith", id=000>, <User: name="Smith John", id=001>, ...] where those <User ...> things represent User objects. Is there reason to use the former over the latter in languages that support it? Or is there some bigger reason to use heterogenous arrays? N.B. I am not talking about arrays that include different objects that all implement the same interface or inherit from the same parent, e.g.: class Square extends Shape class Triangle extends Shape [new Square(), new Triangle()] because that is, to the programmer at least, still a homogenous array as you'll be doing the same thing with each shape (e.g., calling the draw() method), only the methods commonly defined between the two.

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• Can I compare a template variable to an integer in Django/App Engine templates?

  - by matt b

  Using Django templates in Google App Engine (on Python), is it possible to compare a template variable to an integer in an {% if %} block? views.py: class MyHandler(webapp.RequestHandler): def get(self): foo_list = db.GqlQuery(...) ... template_values['foos'] = foo_list template_values['foo_count'] = len(foo_list) handler.response.out.write(template.render(...)) My template: {% if foo_count == 1 %} There is one foo. {% endif %} This blows up with 'if' statement improperly formatted. What I was attempting to do in my template was build a simple if/elif/else tree to be grammatically correct to be able to state #foo_count == 0: There are no foos. #foo_count == 1: There is one foo. #else: There are {{ foos|length }} foos. Browsing the Django template documents (this link provided in the GAE documentation appears to be for versions of Django far newer than what is supported on GAE), it appears as if I can only actually use boolean operators (if in fact boolean operators are supported in this older version of Django) with strings or other template variables. Is it not possible to compare variables to integers or non-strings with Django templates? I'm sure there is an easy way to workaround this - built up the message string on the Python side rather than within the template - but this seems like such a simple operation you ought to be able to handle in a template. It sounds like I should be switching to a more advanced templating engine, but as I am new to Django (templates or any part of it), I'd just like some confirmation first.

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• error in a pygame code

  - by mekasperasky

  # INTIALISATION import pygame, math, sys from pygame.locals import * screen = pygame.display.set_mode((1024, 768)) car = pygame.image.load('car.png') clock = pygame.time.Clock() k_up = k_down = k_left = k_right = 0 speed = direction = 0 position = (100, 100) TURN_SPEED = 5 ACCELERATION = 2 MAX_FORWARD_SPEED = 10 MAX_REVERSE_SPEED = ­5 BLACK = (0,0,0) while 1: # USER INPUT clock.tick(30) for event in pygame.event.get(): if not hasattr(event, 'key'): continue down = event.type == KEYDOWN # key down or up? if event.key == K_RIGHT: k_right = down * ­5 elif event.key == K_LEFT: k_left = down * 5 elif event.key == K_UP: k_up = down * 2 elif event.key == K_DOWN: k_down = down * ­2 elif event.key == K_ESCAPE: sys.exit(0) # quit the game screen.fill(BLACK) # SIMULATION # .. new speed and direction based on acceleration and turn speed += (k_up + k_down) if speed > MAX_FORWARD_SPEED: speed = MAX_FORWARD_SPEED if speed < MAX_REVERSE_SPEED: speed = MAX_REVERSE_SPEED direction += (k_right + k_left) # .. new position based on current position, speed and direction x, y = position rad = direction * math.pi / 180 x += ­speed*math.sin(rad) y += ­speed*math.cos(rad) position = (x, y) # RENDERING # .. rotate the car image for direction rotated = pygame.transform.rotate(car, direction) # .. position the car on screen rect = rotated.get_rect() rect.center = position # .. render the car to screen screen.blit(rotated, rect) pygame.display.flip() enter code here the error i get is this Non-ASCII character '\xc2' in file race1.py on line 13, but no encoding declared; see http://www.python.org/peps/pep-0263.html for details Not able to understand what the error is and how to get rid of it?

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• Dynamically add items to Tkinter Canvas

  - by nick369

  I'm attempting to learn Tkinter with the goal of being able to create a 'real-time' scope to plot data. As a test, I'm trying to draw a polygon on the canvas every time the 'draw' button is pressed. The triangle position is randomized. I have two problems: There is a triangle on the canvas as soon as the program starts, why and how do I fix this? It doesn't draw any triangles when I press the button, at least none that I can see. CODE from Tkinter import * from random import randint class App: def __init__(self,master): #frame = Frame(master) #frame.pack(side = LEFT) self.plotspc = Canvas(master,height = 100, width = 200, bg = "white") self.plotspc.grid(row=0,column = 2, rowspan = 5) self.button = Button(master, text = "Quit", fg = "red", \ command = master.quit) self.button.grid(row=0,column=0) self.drawbutton = Button(master, text = "Draw", command = \ self.pt([50,50])) self.drawbutton.grid(row = 0, column = 1) def pt(self, coords): coords[0] = coords[0] + randint(-20,20) coords[1] = coords[1] + randint(-20,20) x = (0,5,10) y = (0,10,0) xp = [coords[0] + xv for xv in x] yp = [coords[1] + yv for yv in y] ptf = zip(xp,yp) self.plotspc.create_polygon(*ptf) if _name_ == "_main_": root = Tk() app = App(root) root.mainloop() The code is formatting strangely within the code tags, I have no idea how to fix this.

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• Django install on a shared host, .htaccess help

  - by redconservatory

  I am trying to install Django on a shared host using the following instructions: docs.google.com/View?docid=dhhpr5xs_463522g My problem is with the following line on my root .htaccess: RewriteRule ^(.*)$ /cgi-bin/wcgi.py/$1 [QSA,L] When I include this line I get a 500 error with almost all of my domains on this account. My cgi-bin directory is home/my-username/public_html/cgi-bin/ The wcgi.py file contains: #!/usr/local/bin/python import os, sys sys.path.insert(0, "/home/username/django/") sys.path.insert(0, "/home/username/django/projects") sys.path.insert(0, "/home/username/django/projects/newprojects") import django.core.handlers.wsgi os.chdir("/home/username/django/projects/newproject") # optional os.environ['DJANGO_SETTINGS_MODULE'] = "newproject.settings" def runcgi(): environ = dict(os.environ.items()) environ['wsgi.input'] = sys.stdin environ['wsgi.errors'] = sys.stderr environ['wsgi.version'] = (1,0) environ['wsgi.multithread'] = False environ['wsgi.multiprocess'] = True environ['wsgi.run_once'] = True application = django.core.handlers.wsgi.WSGIHandler() if environ.get('HTTPS','off') in ('on','1'): environ['wsgi.url_scheme'] = 'https' else: environ['wsgi.url_scheme'] = 'http' headers_set = [] headers_sent = [] def write(data): if not headers_set: raise AssertionError("write() before start_response()") elif not headers_sent: # Before the first output, send the stored headers status, response_headers = headers_sent[:] = headers_set sys.stdout.write('Status: %s\r\n' % status) for header in response_headers: sys.stdout.write('%s: %s\r\n' % header) sys.stdout.write('\r\n') sys.stdout.write(data) sys.stdout.flush() def start_response(status,response_headers,exc_info=None): if exc_info: try: if headers_sent: # Re-raise original exception if headers sent raise exc_info[0], exc_info[1], exc_info[2] finally: exc_info = None # avoid dangling circular ref elif headers_set: raise AssertionError("Headers already set!") headers_set[:] = [status,response_headers] return write result = application(environ, start_response) try: for data in result: if data: # don't send headers until body appears write(data) if not headers_sent: write('') # send headers now if body was empty finally: if hasattr(result,'close'): result.close() runcgi() Only I changed the "username" to my username...

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• Webfaction apache + mod_wsgi + django configuration issue

  - by Dmitry Guyvoronsky

  A problem that I stumbled upon recently, and, even though I solved it, I would like to hear your opinion of what correct/simple/adopted solution would be. I'm developing website using Django + python. When I run it on local machine with "python manage.py runserver", local address is http://127.0.0.1:8000/ by default. However, on production server my app has other url, with path - like "http://server.name/myproj/" I need to generate and use permanent urls. If I'm using {% url view params %}, I'm getting paths that are relative to / , since my urls.py contains this urlpatterns = patterns('', (r'^(\d+)?$', 'myproj.myapp.views.index'), (r'^img/(.*)$', 'django.views.static.serve', {'document_root': settings.MEDIA_ROOT + '/img' }), (r'^css/(.*)$', 'django.views.static.serve', {'document_root': settings.MEDIA_ROOT + '/css' }), ) So far, I see 2 solutions: modify urls.py, include '/myproj/' in case of production run use request.build_absolute_uri() for creating link in views.py or pass some variable with 'hostname:port/path' in templates Are there prettier ways to deal with this problem? Thank you. Update: Well, the problem seems to be not in django, but in webfaction way to configure wsgi. Apache configuration for application with URL "hostname.com/myapp" contains the following line WSGIScriptAlias / /home/dreamiurg/webapps/pinfont/myproject.wsgi So, SCRIPT_NAME is empty, and the only solution I see is to get to mod_python or serve my application from root. Any ideas?

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• Use Django ORM as standalone [closed]

  - by KeyboardInterrupt

  Possible Duplicates: Use only some parts of Django? Using only the DB part of Django I want to use the Django ORM as standalone. Despite an hour of searching Google, I'm still left with several questions: Does it require me to set up my Python project with a setting.py, /myApp/ directory, and modules.py file? Can I create a new models.py and run syncdb to have it automatically setup the tables and relationships or can I only use models from existing Django projects? There seems to be a lot of questions regarding PYTHONPATH. If you're not calling existing models is this needed? I guess the easiest thing would be for someone to just post a basic template or walkthrough of the process, clarifying the organization of the files e.g.: db/ __init__.py settings.py myScript.py orm/ __init__.py models.py And the basic essentials: # settings.py from django.conf import settings settings.configure( DATABASE_ENGINE = "postgresql_psycopg2", DATABASE_HOST = "localhost", DATABASE_NAME = "dbName", DATABASE_USER = "user", DATABASE_PASSWORD = "pass", DATABASE_PORT = "5432" ) # orm/models.py # ... # myScript.py # import models.. And whether you need to run something like: django-admin.py inspectdb ... (Oh, I'm running Windows if that changes anything regarding command-line arguments.).

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• small code redundancy within while-loops (doesn't feel clean)

  - by wallacoloo

  So, in Python (though I think it can be applied to many languages), I find myself with something like this quite often: the_input = raw_input("what to print?\n") while the_input != "quit": print the_input the_input = raw_input("what to print?\n") Maybe I'm being too picky, but I don't like how the line the_input = raw_input("what to print?\n") has to get repeated. It decreases maintainability and organization. But I don't see any workarounds for avoiding the duplicate code without further decreasing the problem. In some languages, I could write something like this: while ((the_input=raw_input("what to print?\n")) != "quit") { print the_input } This is definitely not Pythonic, and Python doesn't even allow for assignment within loop conditions AFAIK. This valid code fixes the redundancy, while 1: the_input = raw_input("what to print?\n") if the_input == "quit": break print the_input But doesn't feel quite right either. The while 1 implies that this loop will run forever; I'm using a loop, but giving it a fake condition and putting the real one inside it. Am I being too picky? Is there a better way to do this? Perhaps there's some language construct designed for this that I don't know of?

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• I need to speed up a function. Should I use cython, ctypes, or something else?

  - by Peter Stewart

  I'm having a lot of fun learning Python by writing a genetic programming type of application. I've had some great advice from Torsten Marek, Paul Hankin and Alex Martelli on this site. The program has 4 main functions: generate (randomly) an expression tree. evaluate the fitness of the tree crossbreed mutate As all of generate, crossbreed and mutate call 'evaluate the fitness'. it is the busiest function and is the primary bottleneck speedwise. As is the nature of genetic algorithms, it has to search an immense solution space so the faster the better. I want to speed up each of these functions. I'll start with the fitness evaluator. My question is what is the best way to do this. I've been looking into cython, ctypes and 'linking and embedding'. They are all new to me and quite beyond me at the moment but I look forward to learning one and eventually all of them. The 'fitness function' needs to compare the value of the expression tree to the value of the target expression. So it will consist of a postfix evaluator which will read the tree in a postfix order. I have all the code in python. I need advice on which I should learn and use now: cython, ctypes or linking and embedding. Thank you.

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• How to learn how to program?

  - by twinbornJoint

  I would like to know the best methods for learning to program. I've been directed towards the Python language because I was told it is good for beginners. I ultimately want to make games for OS X/iPhone. My problem is that I understand what I read but I can't apply my knowledge to anything. I am a programming noob. Should I stick with Python? (is there a better language I should be learning?) Where can I learn programming theory? I get very hyper when reading my book sometimes, any tips on staying calm and focusing? What are effective ways to learn how to program? Are there standard exercises for programming? (I feel solving problems helps my understanding immensely) Ultimately I feel like I am in a never ending tunnel that leads me no where. It feels like I am just completely unable to pursue anything in the world of programming, yet it is something I want to do very much. Thanks.

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

  - by Julian

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

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• Pairs from single list

  - by Apalala

  Often enough, I've found the need to process a list by pairs. I was wondering which would be the pythonic and efficient way to do it, and found this on Google: pairs = zip(t[::2], t[1::2]) I thought that was pythonic enough, but after a recent discussion involving idioms versus efficiency, I decided to do some tests: import time from itertools import islice, izip def pairs_1(t): return zip(t[::2], t[1::2]) def pairs_2(t): return izip(t[::2], t[1::2]) def pairs_3(t): return izip(islice(t,None,None,2), islice(t,1,None,2)) A = range(10000) B = xrange(len(A)) def pairs_4(t): # ignore value of t! t = B return izip(islice(t,None,None,2), islice(t,1,None,2)) for f in pairs_1, pairs_2, pairs_3, pairs_4: # time the pairing s = time.time() for i in range(1000): p = f(A) t1 = time.time() - s # time using the pairs s = time.time() for i in range(1000): p = f(A) for a, b in p: pass t2 = time.time() - s print t1, t2, t2-t1 These were the results on my computer: 1.48668909073 2.63187503815 1.14518594742 0.105381965637 1.35109519958 1.24571323395 0.00257992744446 1.46182489395 1.45924496651 0.00251388549805 1.70076990128 1.69825601578 If I'm interpreting them correctly, that should mean that the implementation of lists, list indexing, and list slicing in Python is very efficient. It's a result both comforting and unexpected. Is there another, "better" way of traversing a list in pairs? Note that if the list has an odd number of elements then the last one will not be in any of the pairs. Which would be the right way to ensure that all elements are included? I added these two suggestions from the answers to the tests: def pairwise(t): it = iter(t) return izip(it, it) def chunkwise(t, size=2): it = iter(t) return izip(*[it]*size) These are the results: 0.00159502029419 1.25745987892 1.25586485863 0.00222492218018 1.23795199394 1.23572707176 Results so far Most pythonic and very efficient: pairs = izip(t[::2], t[1::2]) Most efficient and very pythonic: pairs = izip(*[iter(t)]*2) It took me a moment to grok that the first answer uses two iterators while the second uses a single one. To deal with sequences with an odd number of elements, the suggestion has been to augment the original sequence adding one element (None) that gets paired with the previous last element, something that can be achieved with itertools.izip_longest().

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• Looking to reimplement build toolchain from bash/grep/sed/awk/(auto)make/configure to something more

  - by wash

  I currently maintain a few boxes that house a loosely related cornucopia of coding projects, databases and repositories (ranging from a homebrew *nix distro to my class notes), maintained by myself and a few equally pasty-skinned nerdy friends (all of said cornucopia is stored in SVN). The vast majority of our code is in C/C++/assembly (a few utilities are in python/perl/php, we're not big java fans), compiled in gcc. Our build toolchain typically consists of a hodgepodge of make, bash, grep, sed and awk. Recent discovery of a Makefile nearly as long as the program it builds (as well as everyone's general anxiety with my cryptic sed and awking) has motivated me to seek a less painful build system. Currently, the strongest candidate I've come across is Boost Build/Bjam as a replacement for GNU make and python as a replacement for our build-related bash scripts. Are there any other C/C++/asm build systems out there worth looking into? I've browsed through a number of make alternatives, but I haven't found any that are developed by names I know aside from Boost's. (I should note that an ability to easily extract information from svn commandline tools such as svnversion is important, as well as enough flexibility to configure for builds of asm projects as easily as c/c++ projects)

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• Rewriting a for loop in pure NumPy to decrease execution time

  - by Statto

  I recently asked about trying to optimise a Python loop for a scientific application, and received an excellent, smart way of recoding it within NumPy which reduced execution time by a factor of around 100 for me! However, calculation of the B value is actually nested within a few other loops, because it is evaluated at a regular grid of positions. Is there a similarly smart NumPy rewrite to shave time off this procedure? I suspect the performance gain for this part would be less marked, and the disadvantages would presumably be that it would not be possible to report back to the user on the progress of the calculation, that the results could not be written to the output file until the end of the calculation, and possibly that doing this in one enormous step would have memory implications? Is it possible to circumvent any of these? import numpy as np import time def reshape_vector(v): b = np.empty((3,1)) for i in range(3): b[i][0] = v[i] return b def unit_vectors(r): return r / np.sqrt((r*r).sum(0)) def calculate_dipole(mu, r_i, mom_i): relative = mu - r_i r_unit = unit_vectors(relative) A = 1e-7 num = A*(3*np.sum(mom_i*r_unit, 0)*r_unit - mom_i) den = np.sqrt(np.sum(relative*relative, 0))**3 B = np.sum(num/den, 1) return B N = 20000 # number of dipoles r_i = np.random.random((3,N)) # positions of dipoles mom_i = np.random.random((3,N)) # moments of dipoles a = np.random.random((3,3)) # three basis vectors for this crystal n = [10,10,10] # points at which to evaluate sum gamma_mu = 135.5 # a constant t_start = time.clock() for i in range(n[0]): r_frac_x = np.float(i)/np.float(n[0]) r_test_x = r_frac_x * a[0] for j in range(n[1]): r_frac_y = np.float(j)/np.float(n[1]) r_test_y = r_frac_y * a[1] for k in range(n[2]): r_frac_z = np.float(k)/np.float(n[2]) r_test = r_test_x +r_test_y + r_frac_z * a[2] r_test_fast = reshape_vector(r_test) B = calculate_dipole(r_test_fast, r_i, mom_i) omega = gamma_mu*np.sqrt(np.dot(B,B)) # write r_test, B and omega to a file frac_done = np.float(i+1)/(n[0]+1) t_elapsed = (time.clock()-t_start) t_remain = (1-frac_done)*t_elapsed/frac_done print frac_done*100,'% done in',t_elapsed/60.,'minutes...approximately',t_remain/60.,'minutes remaining'

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• Custom Server to communicate with my software?

  - by Zachary Brown

  I am working on a major project that I need for work. I am working on a project that requires software validation. I would like this to be handled by a custom server I will write in Python, this server will be the "gateway" between the user and product activation. The software program will be purchased from other companies in volume licensing. So this is what I need the server to do: 1). The user clicks to activate their software. (easy, all is good so far) 2). The software gets the distributor's id from another online server. ( this is also easy, and already coded.) 3). Then, the software asks my custom server if the distributor is allowed to activate anymore copies of the software. 4). The server will then check ( an online encoded text file ) to see if the distributor can or can't. If they can, it will tell the software that registration can proceede, at which point the software will pass the software serial number to the server. I have done my best to explain what I am trying to accomplish, but if something is not quite sensible, please let me know. Thanks to all members of Stackoverflow.com for the help in the past, and those who will help me now. I am using Python 2.6 Win. XP Home Edition

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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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• Pymedia video encoding failed

  - by user1474837

  I am using Python 2.5 with Windows XP. I am trying to make a list of pygame images into a video file using this function. I found the function on the internet and edited it. It worked at first, than it stopped working. This is what it printed out: Making video... Formating 114 Frames... starting loop making encoder Frame 1 process 1 Frame 1 process 2 Frame 1 process 2.5 This is the error: Traceback (most recent call last): File "ScreenCapture.py", line 202, in <module> makeVideoUpdated(record_files, video_file) File "ScreenCapture.py", line 151, in makeVideoUpdated d = enc.encode(da) pymedia.video.vcodec.VCodecError: Failed to encode frame( error code is 0 ) This is my code: def makeVideoUpdated(files, outFile, outCodec='mpeg1video', info1=0.1): fw = open(outFile, 'wb') if (fw == None) : print "Cannot open file " + outFile return if outCodec == 'mpeg1video' : bitrate= 2700000 else: bitrate= 9800000 start = time.time() enc = None frame = 1 print "Formating "+str(len(files))+" Frames..." print "starting loop" for img in files: if enc == None: print "making encoder" params= {'type': 0, 'gop_size': 12, 'frame_rate_base': 125, 'max_b_frames': 90, 'height': img.get_height(), 'width': img.get_width(), 'frame_rate': 90, 'deinterlace': 0, 'bitrate': bitrate, 'id': vcodec.getCodecID(outCodec) } enc = vcodec.Encoder(params) # Create VFrame print "Frame "+str(frame)+" process 1" bmpFrame= vcodec.VFrame(vcodec.formats.PIX_FMT_RGB24, img.get_size(), # Covert image to 24bit RGB (pygame.image.tostring(img, "RGB"), None, None) ) print "Frame "+str(frame)+" process 2" # Convert to YUV, then codec da = bmpFrame.convert(vcodec.formats.PIX_FMT_YUV420P) print "Frame "+str(frame)+" process 2.5" d = enc.encode(da) #THIS IS WHERE IT STOPS print "Frame "+str(frame)+" process 3" fw.write(d.data) print "Frame "+str(frame)+" process 4" frame += 1 print "savng file" fw.close() Could somebody tell me why I have this error and possibly how to fix it? The files argument is a list of pygame images, outFile is a path, outCodec is default, and info1 is not used anymore. UPDATE 1 This is the code I used to make that list of pygame images. from PIL import ImageGrab import time, pygame pygame.init() f = [] #This is the list that contains the images fps = 1 for n in range(1, 100): info = ImageGrab.grab() size = info.size mode = info.mode data = info.tostring() info = pygame.image.fromstring(data, size, mode) f.append(info) time.sleep(fps)

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• Fake serial communication under Linux

  - by kigurai

  I have an application where I want to simulate the connection between a device and a "modem". The device will be connected to a serial port and will talk to the software modem through that. For testing purposes I want to be able to use a mock software device to test send and receive data. Example Python code device = Device() modem = Modem() device.connect(modem) device.write("Hello") modem_reply = device.read() Now, in my final app I will just pass /dev/ttyS1 or COM1 or whatever for the application to use. But how can I do this in software? I am running Linux and application is written in Python. I have tried making a FIFO (mkfifo ~/my_fifo) and that does work, but then I'll need one FIFO for writing and one for reading. What I want is to open ~/my_fake_serial_port and read and write to that. I have also lpayed with the ptymodule, but can't get that to work either. I can get a master and slave file descriptor from pty.openpty() but trying to read or write to them only causes IOError Bad File Descriptor error message.

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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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• JavaScript cookie value can't be retrieved in Django

  - by Boris Rusev

  I am trying to build a web site in both English and Bulgarian using the Django framework. My idea is the user should click on a button, the page will reload and the language will be changed. This is how I am trying to do it: In my html I hava a the button tag <button id='btn' onclick="changeLanguage();" type="button"> ... </button> An excerpt from cookies.js: function changeLanguage() { if (getCookie('language') == 'EN') { document.getElementById('btn').innerHTML = getCookie('language'); setCookie("language", 'BG'); } else { document.getElementById('btn').innerHTML = getCookie('language'); setCookie("language", 'EN'); } } function setCookie(sName, sValue, oExpires, sPath, sDomain, bSecure) { var sCookie = sName + "=" + encodeURIComponent(sValue); if (oExpires) { sCookie += "; expires=" + oExpires.toGMTString(); } if (sPath) { sCookie += "; path=" + sPath; } if (sDomain) { sCookie += "; domain=" + sDomain; } if (bSecure) { sCookie += "; secure"; } document.cookie = sCookie; } And in my views.py file this is the situation @base def index(request): if request.session['language'] == 'EN': return """<b>%s</b>""" % "Home" else request.session['language'] == 'BG': return """<b>%s</b>""" % "??????" So I know that my JS changes the value of the language cookie but I think Django doesn't get that. On the other hand when I set and get the cookie in my Python code again the cookie is set. My question is whether there is a way to make JS and Django work together - JavaScript sets the cookie value and Python only reads it when asked and takes adequate actions? Thank you.

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• Splitting 25mb .txt file into smaller files using text delimiter

  - by user574141

  Regards, SO I am new to python and Perl. I have been trying to solve a simple problem and getting tied in knots with syntax. I hope someone has the time and patience to help. I have a 25mb file in ".txt" format which contains news-wire articles going back to 1970. Each news story is concatenated to the next, with only the "Copyright" statement to delimit. Each news story starts with "Item XX of XXX DOCUMENTS". There are certain metadata that are repeated throughout, I will use these for tagging later on. I wish to split this 25mb file into separate .txt files, each containing one news story (i.e. the text between "DOCUMENTS" and "Copyright", saving each with a different name (obviously). I am trying to 1 ) open the file... 2) iterate over lines in the file checking for the eof delimiter, and if it is not present writing the line to a list 3)write that list to a seperate small file. I'm having big problems with changing filenames using the counter, and how do I make Python start from where I left off, is the "seek" function appropriate? so far I have been trying this approach, completely unsuccessfully: myfile = open ("myfile.txt", 'r') filenumber = 0 for line in myfile.readline(): filenumber += 1 w=0 while myfile.readline() != '\s+DOCUMENTS\s*\n' ### read my line into a list mysmallfile()['w'] = [myfile.readline()] w += 1 output = open('C:\\Users\\dunner7\\Documents\###how do I change the filename each iteration???', 'w') output.writelines(mysmallfile) ###go back to start. Thank you for your time and patience. RD

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• Emptying the datastore in GAE

  - by colwilson

  I know what you're thinking, 'O not that again!', but here we are since Google have not yet provided a simpler method. I have been using a queue based solution which worked fine: import datetime from models import * DELETABLE_MODELS = [Alpha, Beta, AlphaBeta] def initiate_purge(): for e in config.DELETABLE_MODELS: deferred.defer(delete_entities, e, 'purging', _queue = 'purging') class NotEmptyException(Exception): pass def delete_entities(e, queue): try: q = e.all(keys_only=True) db.delete(q.fetch(200)) ct = q.count(1) if ct > 0: raise NotEmptyException('there are still entities to be deleted') else: logging.info('processing %s completed' % queue) except Exception, err: deferred.defer(delete_entities, e, then, queue, _queue = queue) logging.info('processing %s deferred: %s' % (queue, err)) All this does is queue a request to delete some data (once for each class) and then if the queued process either fails or knows there is still some stuff to delete, it re-queues itself. This beats the heck out of hitting the refresh on a browser for 10 minutes. However, I'm having trouble deleting AlphaBeta entities, there are always a few left at the end. I think because it contains Reference Properties: class AlphaBeta(db.Model): alpha = db.ReferenceProperty(Alpha, required=True, collection_name='betas') beta = db.ReferenceProperty(Beta, required=True, collection_name='alphas') I have tried deleting the indexes relating to these entity types, but that did not make any difference. Any advice would be appreciated please.

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• Help me write my LISP :) LISP environments, Ruby Hashes...

  - by MikeC8

  I'm implementing a rudimentary version of LISP in Ruby just in order to familiarize myself with some concepts. I'm basing my implementation off of Peter Norvig's Lispy (http://norvig.com/lispy.html). There's something I'm missing here though, and I'd appreciate some help... He subclasses Python's dict as follows: class Env(dict): "An environment: a dict of {'var':val} pairs, with an outer Env." def __init__(self, parms=(), args=(), outer=None): self.update(zip(parms,args)) self.outer = outer def find(self, var): "Find the innermost Env where var appears." return self if var in self else self.outer.find(var) He then goes on to explain why he does this rather than just using a dict. However, for some reason, his explanation keeps passing in through my eyes and out through the back of my head. Why not use a dict, and then inside the eval function, when a new "sub-environment" needs to be created, just take the existing dict and update the key/value pairs that need to be updated, and pass that new dict into the next eval? Won't the Python interpreter keep track of the previous "outer" envs? And won't the nature of the recursion ensure that the values are pulled out from "inner" to "outer"? I'm using Ruby, and I tried to implement things this way. Something's not working though, and it might be because of this, or perhaps not. Here's my eval function, env being a regular Hash: def eval(x, env = $global_env) ........ elsif x[0] == "lambda" then ->(*args) { eval(x[2], env.merge(Hash[*x[1].zip(args).flatten(1)])) } ........ end The line that matters of course is the "lambda" one. If there is a difference, what's importantly different between what I'm doing here and what Norvig did with his Env class? If there's no difference, then perhaps someone can enlighten me as to why Norvig uses the Env class. Thanks :)

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• Capturing stdout from an imported module in wxpython and sending it to a textctrl, without blocking the GUI

  - by splafe

  There are alot of very similar questions to this but I can't find one that applies specifically to what I'm trying to do. I have a simulation (written in SimPy) that I'm writing a GUI for, the main output of the simulation is text - to the console from 'print' statements. Now, I thought the simplest way would be to create a seperate module GUI.py, and import my simulation program into it: import osi_model I want all the print statements to be captured by the GUI and appear inside a Textctrl, which there's countless examples of on here, along these lines: class MyFrame(wx.Frame): def __init__(self, *args, **kwds): <general frame initialisation stuff..> redir=RedirectText(self.txtCtrl_1) sys.stdout=redir class RedirectText: def __init__(self,aWxTextCtrl): self.out=aWxTextCtrl def write(self,string): self.out.WriteText(string) I am also starting my simulation from a 'Go' button: def go_btn_click(self, event): print 'GO' self.RT = threading.Thread(target=osi_model.RunThis()) self.RT.start() This all works fine, and the output from the simulation module is captured by the TextCtrl, except the GUI locks up and becomes unresponsive - I still need it to be accessible (at the very minimum to have a 'Stop' button). I'm not sure if this is a botched attempt at creating a new thread that I've done here, but I assume a new thread will be needed at some stage in this process. People suggest using wx.CallAfter, but I'm not sure how to go about this considering the imported module doesn't know about wx, and also I can't realistically go through the entire simulation architecture and change all the print statements to wx.CallAfter, and any attempt to capture the shell from inside the imported simulation program leads to the program crashing. Does anybody have any ideas about how I can best achieve this? So all I really need is for all console text to be captured by a TextCtrl while the GUI remains responsive, and all text is solely coming from an imported module. (Also, secondary question regarding a Stop button - is it bad form to just kill the simulation thread?). Thanks, Duncan

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