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• What is the best way to build a database from a MS Word document?

  - by Jayron Soares

  Please advise me on how to approach this problem: I have a sequential list of metadata in a document in MS Word. The basic idea is to create a Python algorithm to iterate over the information, retrieving just the name of the PROCESS, when is made a queue, from a database. Example metadata: Process: Process Walker (1965) Exact reference: Walker Process Equipment., Inc. v. Food Machinery Corp. Link: http://caselaw.lp.findlaw.com/scripts/getcase.pl?court=US&vol=382&invol= Type of procedure: Certiorari to the United States Court of Appeals for the Seventh Circuit. Parties: Walker Process Equipment, Inc. Sector: Systems is ... Start Date: October 12-13 Arguedas, 1965 Summary: Food Machinery Company has initiated a process to stop or slow the entry of competitors through the use of a patent obtained by fraud. The case concerned a patent on "knee action swing diffusers" used in aeration equipment for sewage treatment systems, and the question was whether "the maintenance and enforcement of a patent obtained by fraud before the patent office" may be a basis for antitrust punishment. Report of the evolution process: petitioner, in answer to respond... Importance: a) First case which established an analysis for the diagnosis of dispute… There are about 200 pages containing the information above. I have in mind the idea of implementing an algorithm in Python to be able to break this information sequence and try to store it in a web database (an open source application that I’m looking for) in order to allow for free consultations.

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• Pygame Tile Based Character movement speed

  - by Ryan

  Thanks for taking the time to read this. Right now I'm making a really basic tile based game. The map is a large amount of 16x16 tiles, and the character image is 16x16 as well. My character has its own class that is an extension of the sprite class, and the x and y position is saved in terms of the tile position. To note I am fairly new to pygame. My question is, I am planning to have character movement restricted to one tile at a time, and I'm not sure how to make it so that, even if the player hits the directional key dozens of time quickly, (WASD or arrow keys) it will only move from tile to tile at a certain speed. How could I implement this generally with pygame? (Similar to game movement of like Pokemon or NexusTk). Edit: I should probably note that I want it so that the player can only end a movement in a tile. He couldn't stop moving halfway inbetween a tile for example. Thanks for your time! Ryan

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• Why use try … finally without a catch clause?

  - by Nick Rosencrantz

  The classical way to program is with try / catch but when is it appropriate to use try without catch? In Python the following appears legal and can make sense: try: #do work finally: #do something unconditional But we didn't catch anything. Similarly one could think in Java it would be try { //for example try to get a database connection } finally { //closeConnection(connection) } It looks good and suddenly I don't have to worry about exception types etc. But if this is good practice, when is it good practice? Or reasons why this is not good practice or not legal (I didn't compile the source I'm asking about and it could be a syntax error for Java but I checked that the Python surely compiles.) A related problem I've run into is that I continue writing the function / method and at the end I must return something and I'm in a place which should not be reached and it must be a return point so even if I handle the exceptions above I'm still returning null or an empty string at some point in the code which should not be reached, often the end of the method / function. I've always managed to restructure to code so that I don't have to return null since that absolutely appears to look like less than good practice.

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• Game software design

  - by L. De Leo

  I have been working on a simple implementation of a card game in object oriented Python/HTML/Javascript and building on the top of Django. At this point the game is in its final stage of development but, while spotting a big issue about how I was keeping the application state (basically using a global variable), I reached the point that I'm stuck. The thing is that ignoring the design flaw, in a single-threaded environment such as under the Django development server, the game works perfectly. While I tried to design classes cleanly and keep methods short I now have in front of me an issue that has been keeping me busy for the last 2 days and that countless print statements and visual debugging hasn't helped me spot. The reason I think has to do with some side-effects of functions and to solve it I've been wondering if maybe refactoring the code entirely with static classes that keep no state and just passing the state around might be a good option to keep side-effects under control. Or maybe trying to program it in a functional programming style (although I'm not sure Python allows for a purely functional style). I feel that now there's already too many layers that the software (which I plan to make incredibly more complex by adding non trivial features) has already become unmanageable. How would you suggest I re-take control of my code-base that (despite being still only at < 1000 LOC) seems to have taken a life of its own?

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• Pythonic Java. Yes, or no?

  - by OscarRyz

  Python use of indentation for code scope was initially very polemic and now is considered one of the best language features, because it helps ( almost by forcing us ) to have a consistent style. Well, I saw this post http://bit.ly/hmvTe9 where someone posted Java code with ; y {} aligned to the right margin to look more pythonic. It was very shocking at first ( as a matter of fact, if I ever see Java code like that in one of my projects I would be scared! ) However, there is something interesting here. Do we need all those braces and semicolons? How would the code would look like without them? class Person int age void greet( String a ) if( a == "" ) out.println("Hello stranger") else out.printf("Hello %s%n", a ) int age() return this.age class Main void main() new Person().greet("") Looks good to me, but in such small piece of code is hard to appreciate it, and since I don't Python too much, I can't tell by looking at existing libraries if it would be cleaner or not. So I took the first file of a library named: jAlarms I found and this is the result: ( WARNING : the following image may be disturbing for some people ) http://pxe.pastebin.com/eU1R4xsh Obviously it doesn't compile. This would be a compiling version using right aligned {} and ; http://pxe.pastebin.com/2uijtbYM Question What would happen if we could code like this? Would it make things clearer? Would it make it harder? I see braces, and semicolons as help to the parser and we, as humans have get used to them, but do we really need them? I guess is hard to tell specially since many mainstream languages do use braces, C, C++, Java, C# JavaScript Assuming the compiler wouldn't have problems without them, would you use them? Please comment.

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• How can I use iteration to lead targets?

  - by e100

  In my 2D game, I have stationary AI turrets firing constant speed bullets at moving targets. So far I have used a quadratic solver technique to calculate where the turret should aim in advance of the target, which works well (see Algorithm to shoot at a target in a 3d game, Predicting enemy position in order to have an object lead its target). But it occurs to me that an iterative technique might be more realistic (e.g. it should fire even when there is no exact solution), efficient and tunable - for example one could change the number of iterations to improve accuracy. I thought I could calculate the current range and thus an initial (inaccurate) bullet flight time to target, then work out where the target would actually be by that time, then recalculate a more accurate range, then recalculate flight time, etc etc. I think I am missing something obvious to do with the time term, but my aimpoint calculation does not currently converge after the significant initial correction in the first iteration: import math def aimpoint(iters, target_x, target_y, target_vel_x, target_vel_y, bullet_speed): aimpoint_x = target_x aimpoint_y = target_y range = math.sqrt(aimpoint_x**2 + aimpoint_y**2) time_to_target = range / bullet_speed time_delta = time_to_target n = 0 while n <= iters: print "iteration:", n, "target:", "(", aimpoint_x, aimpoint_y, ")", "time_delta:", time_delta aimpoint_x += target_vel_x * time_delta aimpoint_y += target_vel_y * time_delta range = math.sqrt(aimpoint_x**2 + aimpoint_y**2) new_time_to_target = range / bullet_speed time_delta = new_time_to_target - time_to_target n += 1 aimpoint(iters=5, target_x=0, target_y=100, target_vel_x=1, target_vel_y=0, bullet_speed=100)

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• puImportError: No module named pyexpat

  - by Candy Gupta

  Whenever I try to launch 'hotot' I get this errors. This error also appears if i try something stupid in terminal along with "No Module named gdm" Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat I am on Ubuntu 12.04 python 2.7.3. I found similar problem here https://github.com/Kindari/SublimeXdebug/issues/5 but did not work. as asked below I am inserting this too ls /usr/lib/python2.7/lib-dynload/ audioop.so _codecs_cn.so _codecs_jp.so crypt.so _ctypes_test.so _elementtree.so _io.so _multibytecodec.so _sqlite3.so _bsddb.so _codecs_hk.so _codecs_kr.so _csv.so _curses_panel.so _heapq.so _json.so _multiprocessing.so _testcapi.so bz2.so _codecs_iso2022.so _codecs_tw.so _ctypes.so _curses.so _hotshot.so _lsprof.so Python-2.7.egg-info

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• Tried teaching myself to program before college, accidently overwhelmed myself, tips?

  - by Gunnar Keith

  I'm sixteen, I'm overly interested in programming, and I'm currently taking IT classes during my mornings in high school. Last year, I tried teaching myself to code. It was quite exciting, but all I did was watch TheNewBoston's videos on YouTube for Python. After his tutorials, I just did research, made some CMD programs, and that's it. After that, I got cocky and got my feet wet in many other languages. Java, C++, C#, Perl, Ruby... and it overwhelmed me. Which made it less fun to code. I want to go to college for a 2 year programming course. And I want to make writing code my profession. But how do you recommend I attack re-learning it all again? Start with Python? Don't even try? Also, I'm not 100% in math, but I'm good friends with a lot of programmers, who say they suck at math, but manage to code just fine. I'm not looking for negative feedback. I just want the proper head-start on things before college.

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• Installing both lxml 3.1.2 and lxml2 on ubuntu 12.04

  - by wgw

  I asked this on SO: http://stackoverflow.com/questions/19852911/lxml-3-1-2-and-lxml2-both-on-ubuntu/19856674#19856674 But it is perhaps more appropriate for AskUbuntu. So here it is again, reformulated. On the lxml site they suggest that it is possible to have both lxml2 and the newest version of lxml on ubuntu: Using lxml with python-libxml2 If you want to use lxml together with the official libxml2 Python bindings (maybe because one of your dependencies uses it), you must build lxml statically. Otherwise, the two packages will interfere in places where the libxml2 library requires global configuration, which can have any kind of effect from disappearing functionality to crashes in either of the two. To get a static build, either pass the --static-deps option to the setup.py script, or run pip with the STATIC_DEPS or STATICBUILD environment variable set to true, i.e. STATIC_DEPS=true pip install lxml The STATICBUILD environment variable is handled equivalently to the STATIC_DEPS variable, but is used by some other extension packages, too. I am generally confused about how pip packages and ubuntu packages get along, so I hesitate to run STATIC_DEPS=true pip install lxml. Will it damage/confuse my installed lxml2 package? The suggestion on SO was to install the new lxml in a virtualenv. That looks like the best way to go, but the lxml site is suggesting that a dual installation will work also. In general: what happens if I use pip (to get a newer install) for a package that is already installed by apt-get?

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• Sendmail encrypted

  - by user1948828

  I manage a website running on Apache. It has public and private areas. When people apply for an account to access the protected portions of the site, they do a TLS/SSL protected POST containing their information which is saved to a (hopefully) nonpublic directory on the server. Then I have a python script which takes URL Encoded POSTS with this user information, sends back a plaintext confirmation to the applicant, encrypts their information with a freeware java command-line utility to protect it (specifically this one: http://spi.dod.mil/ewizard.htm), base64 encodes them, puts them in a file as a mime attachment and uses sendmail to forward the file information to my (and several coworkers' scattered around the country) email account(s) on an Exchange server with Outlook clients. This has worked well for years, but is awkward because it involves manually decrypting the information on a windows box once it is received, using the above mentioned encryption utility. This significantly limits how many can be processed. I would like to be able to encrypt my information in a format that Outlook/Exchange can inherently understand and display so that these emails can be viewed simply by clicking on them. I do have company provided PKI public certs for all the people I need to send to, and am able to send/receive encrypted emails on Outlook manually, but would like to know how I can send to Outlook from apache/linux/python from the command line using the same PKI certs. Dont need to receive them, just send. Is there a utility that can do this? I had thought pgp might but I havent been able to figure it out.

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• Most efficient way to implement delta time

  - by Starkers

  Here's one way to implement delta time: /// init /// var duration = 5000, currentTime = Date.now(); // and create cube, scene, camera ect ////// function animate() { /// determine delta /// var now = Date.now(), deltat = now - currentTime, currentTime = now, scalar = deltat / duration, angle = (Math.PI * 2) * scalar; ////// /// animate /// cube.rotation.y += angle; ////// /// update /// requestAnimationFrame(render); ////// } Could someone confirm I know how it works? Here what I think is going on: Firstly, we set duration at 5000, which how long the loop will take to complete in an ideal world. With a computer that is slow/busy, let's say the animation loop takes twice as long as it should, so 10000: When this happens, the scalar is set to 2.0: scalar = deltat / duration scalar = 10000 / 5000 scalar = 2.0 We now times all animation by twice as much: angle = (Math.PI * 2) * scalar; angle = (Math.PI * 2) * 2.0; angle = (Math.PI * 4) // which is 2 rotations When we do this, the cube rotation will appear to 'jump', but this is good because the animation remains real-time. With a computer that is going too quickly, let's say the animation loop takes half as long as it should, so 2500: When this happens, the scalar is set to 0.5: scalar = deltat / duration scalar = 2500 / 5000 scalar = 0.5 We now times all animation by a half: angle = (Math.PI * 2) * scalar; angle = (Math.PI * 2) * 0.5; angle = (Math.PI * 1) // which is half a rotation When we do this, the cube won't jump at all, and the animation remains real time, and doesn't speed up. However, would I be right in thinking this doesn't alter how hard the computer is working? I mean it still goes through the loop as fast as it can, and it still has render the whole scene, just with different smaller angles! So this a bad way to implement delta time, right? Now let's pretend the computer is taking exactly as long as it should, so 5000: When this happens, the scalar is set to 1.0: angle = (Math.PI * 2) * scalar; angle = (Math.PI * 2) * 1; angle = (Math.PI * 2) // which is 1 rotation When we do this, everything is timsed by 1, so nothing is changed. We'd get the same result if we weren't using delta time at all! My questions are as follows Mostly importantly, have I got the right end of the stick here? How do we know to set the duration to 5000 ? Or can it be any number? I'm a bit vague about the "computer going too quickly". Is there a way loop less often rather than reduce the animation steps? Seems like a better idea. Using this method, do all of our animations need to be timesed by the scalar? Do we have to hunt down every last one and times it? Is this the best way to implement delta time? I think not, due to the fact the computer can go nuts and all we do is divide each animation step and because we need to hunt down every step and times it by the scalar. Not a very nice DSL, as it were. So what is the best way to implement delta time? Below is one way that I do not really get but may be a better way to implement delta time. Could someone explain please? // Globals INV_MAX_FPS = 1 / 60; frameDelta = 0; clock = new THREE.Clock(); // In the animation loop (the requestAnimationFrame callback)… frameDelta += clock.getDelta(); // API: "Get the seconds passed since the last call to this method." while (frameDelta >= INV_MAX_FPS) { update(INV_MAX_FPS); // calculate physics frameDelta -= INV_MAX_FPS; } How I think this works: Firstly we set INV_MAX_FPS to 0.01666666666 How we will use this number number does not jump out at me. We then intialize a frameDelta which stores how long the last loop took to run. Come the first loop frameDelta is not greater than INV_MAX_FPS so the loop is not run (0 = 0.01666666666). So nothing happens. Now I really don't know what would cause this to happen, but let's pretend that the loop we just went through took 2 seconds to complete: We set frameDelta to 2: frameDelta += clock.getDelta(); frameDelta += 2.00 Now we run an animation thanks to update(0.01666666666). Again what is relevance of 0.01666666666?? And then we take away 0.01666666666 from the frameDelta: frameDelta -= INV_MAX_FPS; frameDelta = frameDelta - INV_MAX_FPS; frameDelta = 2 - 0.01666666666 frameDelta = 1.98333333334 So let's go into the second loop. Let's say it took 2(? Why not 2? Or 12? I am a bit confused): frameDelta += clock.getDelta(); frameDelta = frameDelta + clock.getDelta(); frameDelta = 1.98333333334 + 2 frameDelta = 3.98333333334 This time we enter the while loop because 3.98333333334 = 0.01666666666 We run update We take away 0.01666666666 from frameDelta again: frameDelta -= INV_MAX_FPS; frameDelta = frameDelta - INV_MAX_FPS; frameDelta = 3.98333333334 - 0.01666666666 frameDelta = 3.96666666668 Now let's pretend the loop is super quick and runs in just 0.1 seconds and continues to do this. (Because the computer isn't busy any more). Basically, the update function will be run, and every loop we take away 0.01666666666 from the frameDelta untill the frameDelta is less than 0.01666666666. And then nothing happens until the computer runs slowly again? Could someone shed some light please? Does the update() update the scalar or something like that and we still have to times everything by the scalar like in the first example?

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• Design pattern for an automated mechanical test bench

  - by JJS

  Background I have a test fixture with a number of communication/data acquisition devices on it that is used as an end of line test for a product. Because of all the various sensors used in the bench and the need to run the test procedure in near real-time, I'm having a hard time structuring the program to be more friendly to modify later on. For example, a National Instruments USB data acquisition device is used to control an analog output (load) and monitor an analog input (current), a digital scale with a serial data interface measures position, an air pressure gauge with a different serial data interface, and the product is interfaced through a proprietary DLL that handles its own serial communication. The hard part The "real-time" aspect of the program is my biggest tripping point. For example, I need to time how long the product needs to go from position 0 to position 10,000 to the tenth of a second. While it's traveling, I need to ramp up an output of the NI DAQ when it reaches position 6,000 and ramp it down when it reaches position 8,000. This sort of control looks easy from browsing NI's LabVIEW docs but I'm stuck with C# for now. All external communication is done by polling which makes for lots of annoying loops. I've slapped together a loose Producer Consumer model where the Producer thread loops through reading the sensors and sets the outputs. The Consumer thread executes functions containing timed loops that poll the Producer for current data and execute movement commands as required. The UI thread polls both threads for updating some gauges indicating current test progress. Unsure where to start Is there a more appropriate pattern for this type of application? Are there any good resources for writing control loops in software (non-LabVIEW) that interface with external sensors and whatnot?

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• Functional programming compared to OOP with classes

  - by luckysmack

  I have been interested in some of the concepts of functional programming lately. I have used OOP for some time now. I can see how I would build a fairly complex app in OOP. Each object would know how to do things that object does. Or anything it's parents class does as well. So I can simply tell Person().speak() to make the person talk. But how do I do similar things in functional programming? I see how functions are first class items. But that function only does one specific thing. Would I simply have a say() method floating around and call it with an equivalent of Person() argument so I know what kind of thing is saying something? So I can see the simple things, just how would I do the comparable of OOP and objects in functional programming, so I can modularize and organize my code base? For reference, my primary experience with OOP is Python, PHP, and some C#. The languages that I am looking at that have functional features are Scala and Haskell. Though I am leaning towards Scala. Basic Example (Python): Animal(object): def say(self, what): print(what) Dog(Animal): def say(self, what): super().say('dog barks: {0}'.format(what)) Cat(Animal): def say(self, what): super().say('cat meows: {0}'.format(what)) dog = Dog() cat = Cat() dog.say('ruff') cat.say('purr')

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• Make the Time

  - by WonderOfItAll

  Took the little one to the pool tonight for swim lessons. Okay, Okay. They're not really lessons so much as they are "Hey, here's a few bucks, let me rent out a small section of your pool to swim around with my little one" Saw a dad at the pool. Bluetooth on, iPad in hand, and two year old somewhere around there. Saw a mom at the pool. Arguing with her five year old to NOT take a shower after swimming. Bluetooth on, iPad in hand, work laptop open on stadium seats. Her reasoning for not wanting the child to shower "Look, I have to get this stuff to the office by 6:30, we don't have time for you to shower. Let's go" Wait, isn't the whole point of this little experience called Mommy and Me (or, as in my case, Daddy and Me). Wherein Mommy/Daddy is supposed to spend time with little one. Not with the Bluetooth. Not with the work laptop. Dad (yeah, the same dad from earlier), in the pool. Bluetooth off (it's not waterproof or I'm sure he would've had it on), two year old in hand and iPad somewhere put away. Getting frustrated with kid because he won't 'perform' on command. Here's a little exchange Kid: "I don't wanna get in the water" Dad: "Well, we're here for 30 minutes, get in the water" Kid: "No, don't wanna" Dad: "Fine, I'm getting in" and, true to his word, in he goes, off to swim. Kid: Crying Dad: "Well, c'mon" Kid: Walking to stands Dad: Ignoring kid Kid: At stands Dad: Out of pool, drying off. Frustrated. Grabs bag, grabs kid, leaves How sad. It really seems like I am living in a generation of parents who view their children as one big scheduled distraction to another. It's almost like the dad was saying "Look, little 2 year old boy, I have a busy scheduled. Right now my Outlook Calendar tells me that I have 30 mins to spend with you, so, let's go kid: PERFORM because I have the time" Really? Can someone please tell me when the hell this happened? When did spending time with your kid, spending time with your family, spending time with your spouse, etc... become a distraction? I've seen people at work all day Tweeting throughout the day, checked in with Four Square, IM up and running constantly so they can 'stay in touch' only to see these same folks come home and be irritated because their kids or their spouse wants to connect with the. I've seen these very same people leave the house, go to the corner bar/store/you-name-the-place to be 'alone' only to find them there, plugged in, tweeting away, etc, etc, etc I LOVE technology. I love working with technology. But I also know that I am a human being. A person who, by very definition, is a social being. I needed social interactions and contact--and, no, I'm not talking about the Social Graph kind of connections, I'm talking about those interactions which, *GASP* involve eye to eye contact and human contact. A recent study found that the number one complaint of kids is that they feel they have to compete with technology for their parents time and attention. The number one wish from high school kids? That there parents would turn off the computer/tv/cell phone at dinner. This, coming from high school kids. Shouldn't that tell you a whole helluva lot? So, do yourself a favor tomorrow. Plug into technology all day. Throw yourself into it. Be passionate about what you do. When you walk through the door to your family, turn it all off for 30 mins and be there with your loved ones. If you can manage to play Angry Birds, I'm sure you can handle being disconnected for 30 minutes. Make the time

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• Splitting Pygame functionality between classes or modules?

  - by sec_goat

  I am attempting to make my pygame application more modular so that different functionalities are split up into different classes and modules. I am having some trouble getting pygame to allow me to draw or load images in secondary classes when the display has been set and pygame.init() has been done in my main class. I have typically used C# and XNA to accomplish this sort of behavior, but this time I need to use python. How do I init pygame in class1, then create an instance of class2 which loads and converts() images. I have tried pygame.init() in class 2 but then it tells me no display mode has been set, when it has been set in class1. I am under the impression i do not wnat to create multiple pygame.displays as that gets problematic I am probably missing something pythonic and simple but I am not sure what. How do I create a Display class, init python and then have other modules do my work like loading images, fonts etc.? here is the simplest version of what I am doing: class1: def __init__(self): self.screen = pygame.display.set_mode((600,400)) self.imageLoader = class2() class2: def __init__(self): self.images = ['list of images'] def load_images(): self.images = os.listdir('./images/') #get all images in the images directory for img in self.images: #read all images in the directory and load them into pygame new_img = pygame.image.load(os.path.join('images', img)).convert() scale_img = pygame.transform.scale(new_img, (pygame.display.Info().current_w, pygame.display.Info().current_h)) self.images.append(scale_img) if __name__ == "__main__": c1 = class1() c1.imageLoader.load_images() Of course when it tries to load an convert the images it tells me pygame has not been initialized, so i throw in a pygame.init() in class2 ( i have heard it is safe to init multiple times) and then the error goes to pygame.error: No video mode has been set

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• I still can't figure out how to program!

  - by Mark K.

  Please help! I've read lots of programming books for various languages, Java, Python, C, etc. I understand and know all of the basics of the languages and I understand algorithms and data structures. (Equivilant of say 2 years of CompSci classes) BUT, I still can't figure how to write a program that does anything useful. All of the programming books show you how to write the language, but NOT how to use it! The programming examples are all very basic like build a card catalog for a library or a simple game or use algorithms etc... They dont't show you how to develop complex programs that actually do anything useful! I've looked a open-source programs on sourceforge, but they don't make much sense to me. There are hundreds of files in each program & thousands of lines of code. But how do I learn how to do this? There's nothing in any book I can buy on Amazon that will give me the tools to write any of these programs. How do you go from reading Intro to Java or Programming Python, or C Programming Language, etc.. to actually being able to say, I have an idea for X Program.. this is how I go about developing it? It seems like there is so much more involved in writing a program than you can learn in a book or from a class. I feel like there is someth Can anyone put me on the right track?

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• Guidelines for creating referentially transparent callables

  - by max

  In some cases, I want to use referentially transparent callables while coding in Python. My goals are to help with handling concurrency, memoization, unit testing, and verification of code correctness. I want to write down clear rules for myself and other developers to follow that would ensure referential transparency. I don't mind that Python won't enforce any rules - we trust ourselves to follow them. Note that we never modify functions or methods in place (i.e., by hacking into the bytecode). Would the following make sense? A callable object c of class C will be referentially transparent if: Whenever the returned value of c(...) depends on any instance attributes, global variables, or disk files, such attributes, variables, and files must not change for the duration of the program execution; the only exception is that instance attributes may be changed during instance initialization. When c(...) is executed, no modifications to the program state occur that may affect the behavior of any object accessed through its "public interface" (as defined by us). If we don't put any restrictions on what "public interface" includes, then rule #2 becomes: When c(...) is executed, no objects are modified that are visible outside the scope of c.__call__. Note: I unsuccessfully tried to ask this question on SO, but I'm hoping it's more appropriate to this site.

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• tips, guidelines, points to remember for rendering professional code?

  - by ronnieaka

  I'm talking about giving clients professional looking code. The whole nine yards, everything you hardcore professional highly experienced programmers here probably do when coding freelance or for the company you work in. I'm fresh out of college and I'm going into freelance. I just want to be sure that my first few projects leave a good after-taste of professionalism imprinted on the clients' minds. When I Googled what i'm asking here, I was given pages that showed various websites and tools that let you make flashy websites and templates etc. The $N package and such stuff. I can't recall the word experts use for it. Standard, framework [i know that's not it]. English isn't my first language so I'm sorry I don't really don't know the exact phrase for it. That abstract way of writing code so that you don't come across as a sloppy programmer. That above mentioned way for programming websites and desktop software [in python/C/C++/Java]. EDIT: i can work on the accruing vast knowledge and know-how and logic building etc. what i'm asking for is the programming standard/guidelines you guys follow so that the client on seeing code feels that its a professional solution. Like comment blocks, a particular indentation style something like that. Is there any book on it or specific list of points for enterprise type coding by them? Especially here as in my case, for building websites [php for now..], and desktop software [c/c++/java/python]

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• How to populate a private container for unit test?

  - by Sardathrion

  I have a class that defines a private (well, __container to be exact since it is python) container. I am using the information within said container as part of the logic of what the class does and have the ability to add/delete the elements of said container. For unit tests, I need to populate this container with some data. That date depends on the test done and thus putting it all in setUp() would be impractical and bloated -- plus it could add unwanted side effects. Since the data is private, I can only add things via the public interface of the object. This run codes that need not be run during a unit test and in some case is just a copy and paste from another test. Currently, I am mocking the whole container but somehow it does not feel that elegant a solution. Due to Python mocking frame work (mock), this requires the container to be public -- so I can use patch.dict(). I would rather keep that data private. What pattern can one use to still populate the containers without excising the public method so I have data to test with? Is there a way to do this with mock' patch.dict() that I missed?

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• Issuing Current Time Increments in StreamInsight (A Practical Example)

  The issuing of a Current Time Increment, Cti, in StreamInsight is very definitely one of the most important concepts to learn if you want your Streams to be responsive. A full discussion of how to issue Ctis is beyond the scope of this article but a very good explanation in addition to Books Online can be found in these three articles by a member of the StreamInsight team at Microsoft, Ciprian Gerea. Time in StreamInsight Series http://blogs.msdn.com/b/streaminsight/archive/2010/07/23/time-in-streaminsight-i.aspx http://blogs.msdn.com/b/streaminsight/archive/2010/07/30/time-in-streaminsight-ii.aspx http://blogs.msdn.com/b/streaminsight/archive/2010/08/03/time-in-streaminsight-iii.aspx A lot of the problems I see with unresponsive or stuck streams on the MSDN Forums are to do with how Ctis are enqueued or in a lot of cases not enqueued. If you enqueue events and never enqueue a Cti then StreamInsight will be perfectly happy. You, on the other hand, will never see data on the output as you have not told StreamInsight to flush the stream. This article deals with a specific implementation problem I had recently whilst working on a StreamInsight project. I look at some possible options and discuss why they would not work before showing the way I solved the problem. The stream of data I was dealing with on this project was very bursty that is to say when events were flowing they came through very quickly and in large numbers (1000 events/sec), but when the stream calmed down it could be a few seconds between each event. When enqueuing events into the StreamInsight engne it is best practice to do so with a StartTime that is given to you by the system producing the event . StreamInsight processes events and it doesn't matter whether those events are being pushed into the engine by a source system or the events are being read from something like a flat file in a directory somewhere. You can apply the same logic and temporal algebra to both situations. Reading from a file is an excellent example of where the time of the event on the source itself is very important. We could be reading that file a long time after it was written. Being able to read the StartTime from the events allows us to define windows that will hold the correct sets of events. I was able to do this with my stream but this is where my problems started. Below is a very simple script to create a SQL Server table and populate it with sample data that will show exactly the problem I had. CREATE TABLE [dbo].[t] ( [c1] [int] PRIMARY KEY, [c2] [datetime] NULL ) INSERT t VALUES (1,'20100810'),(2,'20100810'),(3,'20100810') Column c2 defines the StartTime of the event on the source and as you can see the values in all 3 rows of data is the same. If we read Ciprian’s articles we know that we can define how Ctis get injected into the stream in 3 different places The Stream Definition The Input Factory The Input Adapter I personally have always been a fan of enqueing Ctis through the factory. Below is code typical of what I would use to do this On the class itself I do some inheriting public class SimpleInputFactory : ITypedInputAdapterFactory<SimpleInputConfig>, ITypedDeclareAdvanceTimeProperties<SimpleInputConfig> And then I implement the following function public AdapterAdvanceTimeSettings DeclareAdvanceTimeProperties<TPayload>(SimpleInputConfig configInfo, EventShape eventShape) { return new AdapterAdvanceTimeSettings( new AdvanceTimeGenerationSettings(configInfo.CtiFrequency, TimeSpan.FromTicks(-1)), AdvanceTimePolicy.Adjust); } The configInfo .CtiFrequency property is a value I pass through to define after how many events I want a Cti to be injected and this in turn will flush through the stream of data. I usually pass a value of 1 for this setting. The second parameter determines the CTI timestamp in terms of a delay relative to the events. -1 ticks in the past results in 1 tick in the future, i.e., ahead of the event. The problem with this method though is that if consecutive events have the same StartTime then only one of those events will be enqueued. In this example I use the following to define how I assign the StartTime of my events currEvent.StartTime = (DateTimeOffset)dt.c2; If I go ahead and run my StreamInsight process with this configuration i can see on the output adapter that two events have been removed To see this in a little more depth I can use the StreamInsight Debugger and see what happens internally. What is happening here is that the first event arrives and a Cti is injected with a time of 1 tick after the StartTime of that event (Also the EndTime of the event). The second event arrives and it has a StartTime of before the Cti and even though we specified AdvanceTimePolicy.Adjust on the factory we know that a point event can never be adjusted like this and the event is dropped. The same happens for the third event as well (The second and third events get trumped by the Cti). For a more detailed discussion of why this happens look here http://www.sqlis.com/sqlis/post/AdvanceTimePolicy-and-Point-Event-Streams-In-StreamInsight.aspx We end up with a single event being pushed into the output adapter and our result now makes sense. The next way I tried to solve this problem by changing the value of the second parameter to TimeSpan.Zero Here is how my factory code now looks public AdapterAdvanceTimeSettings DeclareAdvanceTimeProperties<TPayload>(SimpleInputConfig configInfo, EventShape eventShape) { return new AdapterAdvanceTimeSettings( new AdvanceTimeGenerationSettings(configInfo.CtiFrequency, TimeSpan.Zero), AdvanceTimePolicy.Adjust); } What I am doing here is declaring a policy that says inject a Cti together with every event and stamp it with a StartTime that is equal to the start time of the event itself (TimeSpan.Zero). This method has plus points as well as a downside. The upside is that no events will be lost by having the same StartTime as previous events. The Downside is that because the Cti is declared with the StartTime of the event itself then it does not actually flush that particular event because in the StreamInsight algebra, a Cti commits only those events that occurred strictly before them. To flush the events we need a Cti to be enqueued with a greater StartTime than the events themselves. Here is what happened when I ran this configuration As you can see all we got through was the Cti and none of the events. The debugger output shows the stamps on the Cti and the events themselves. Because the Cti issued has the same timestamp (StartTime) as the events then none of the events get flushed. I was nearly there but not quite. Because my stream was bursty it was possible that the next event would not come along for a few seconds and this was far too long for an event to be enqueued and not be flushed to the output adapter. I needed another solution. Two possible solutions crossed my mind although only one of them made sense when I explored it some more. Where multiple events have the same StartTime I could add 1 tick to the first event, two to the second, three to third etc thereby giving them unique StartTime values. Add a timer to manually inject Ctis The problem with the first implementation is that I would be giving the events a new StartTime. This would cause me the following problems If I want to define windows over the stream then some events may not be captured in the right windows and therefore any calculations on those windows I did would be wrong What would happen if we had 10,000 events with the same StartTime? I would enqueue them with StartTime + n ticks. Along comes a genuine event with a StartTime of the very first event + 1 tick. It is now too far in the past as far as my stream is concerned and it would be dropped. Not what I would want to do at all. I decided then to look at the Timer based solution I created a timer on my input adapter that elapsed every 200ms. private Timer tmr; public SimpleInputAdapter(SimpleInputConfig configInfo) { ctx = new SimpleTimeExtractDataContext(configInfo.ConnectionString); this.configInfo = configInfo; tmr = new Timer(200); tmr.Elapsed += new ElapsedEventHandler(t_Elapsed); tmr.Enabled = true; } void t_Elapsed(object sender, ElapsedEventArgs e) { ts = DateTime.Now - dtCtiIssued; if (ts.TotalMilliseconds >= 200 && TimerIssuedCti == false) { EnqueueCtiEvent(System.DateTime.Now.AddTicks(-100)); TimerIssuedCti = true; } }   In the t_Elapsed event handler I find out the difference in time between now and when the last event was processed (dtCtiIssued). I then check to see if that is greater than or equal to 200ms and if the last issuing of a Cti was done by the timer or by a genuine event (TimerIssuedCti). If I didn’t do this check then I would enqueue a Cti every time the timer elapsed which is not something I wanted. If the difference between the two times is greater than or equal to 500ms and the last event enqueued was by a real event then I issue a Cti through the timer to flush the event Queue, otherwise I do nothing. When I enqueue the Ctis into my stream in my ProduceEvents method I also set the values of dtCtiIssued and TimerIssuedCti   currEvent = CreateInsertEvent(); currEvent.StartTime = (DateTimeOffset)dt.c2; TimerIssuedCti = false; dtCtiIssued = currEvent.StartTime; If I go ahead and run this configuration I see the following in my output. As we can see the first Cti gets enqueued as before but then another is enqueued by the timer and because this has a later timestamp it flushes the enqueued events through the engine. Conclusion Hopefully this has shown how the enqueuing of Ctis can have a dramatic effect on the responsiveness of your output in StreamInsight. Understanding the temporal nature of the product is for me one of the most important things you can learn. I have attached my solution for the demos. It is all in one project and testing each variation is a simple matter of commenting and un-commenting the parts in the code we have been dealing with here.

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• Accelerate your SOA with Data Integration - Live Webinar Tuesday!

  - by dain.hansen

  Need to put wind in your SOA sails? Organizations are turning more and more to Real-time data integration to complement their Service Oriented Architecture. The benefit? Lowering costs through consolidating legacy systems, reducing risk of bad data polluting their applications, and shortening the time to deliver new service offerings. Join us on Tuesday April 13th, 11AM PST for our live webinar on the value of combining SOA and Data Integration together. In this webcast you'll learn how to innovate across your applications swiftly and at a lower cost using Oracle Data Integration technologies: Oracle Data Integrator Enterprise Edition, Oracle GoldenGate, and Oracle Data Quality. You'll also hear: Best practices for building re-usable data services that are high performing and scalable across the enterprise How real-time data integration can maximize SOA returns while providing continuous availability for your mission critical applications Architectural approaches to speed service implementation and delivery times, with pre-integrations to CRM, ERP, BI, and other packaged applications Register now for this live webinar!

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• Best way to store a large amount of game objects and update the ones onscreen

  - by user3002473

  Good afternoon guys! I'm a young beginner game developer working on my first large scale game project and I've run into a situation where I'm not quite sure what the best solution may be (if there is a lone solution). The question may be vague (if anyone can think of a better title after having read the question, please edit it) or broad but I'm not quite sure what to do and I thought it would help just to discuss the problem with people more educated in the field. Before we get started, here are some of the questions I've looked at for help in the past: Best way to keep track of game objects Elegant way to simulate large amounts of entities within a game world What is the most efficient container to store dynamic game objects in? I've also read articles about different data structures commonly used in games to store game objects such as this one about slot maps, but none of them are really what I'm looking for. Also, if it helps at all I'm using Python 3 to design the game. It has to be Python 3, if I could I would use C++ or Unityscript or something else, but I'm restricted to having to use Python 3. My game will be a form of side scroller shooter game. In said game the player will traverse large rooms with large amounts of enemies and other game objects to update (think some of the larger areas in Cave Story or Iji). The player obviously can't see the entire room all at once, so there is a viewport that follows the player around and renders only a selection of the room and the game objects that it contains. This is not a foreign concept. The part that's getting me confused has to do with how certain game objects are updated. Some of them are to be updated constantly, regardless of whether or not they can be seen. Other objects however are only to be updated when they are onscreen (for example, an enemy would only be updated to react to the player when it is onscreen or when it is in a certain range of the screen). Another problem is that game objects have to be easily referable by other game objects; something that happens in the player's update() method may affect another object in the world. Collision detection in games is always a serious problem. I need a way of containing the game objects such that it minimizes the number of cases when testing for collisions against one another. The final problem is that of creating and destroying game objects. I think this problem is pretty self explanatory. To store the game objects then I've considered a number of different methods. The original method I had was to simply store all the objects in a hash table by an id. This method was simple, and decently fast as it allows all the objects to be looked up in O(1) complexity, and also allows them to be deleted fairly easily. Hash collisions would not be a major problem; I wasn't originally planning on using computer generated ids to store the game objects I was going to rely on them all using ids given to them by the game designer (such names would be strings like 'Player' or 'EnemyWeapon4'), and even if I did use computer generated ids, if I used a decent hashing algorithm then the chances of collisions would be around 1 in 4 billion. The problem with using a hash table however is that it is inefficient in checking to see what objects are in range of the viewport. Considering the fact that certain game objects move (as well as the viewport itself), the only solution I could think of in order to only update objects that are in the viewport would be to iterate through every object in the hash table and check if it is in the viewport or not, updating only the ones that are in the valid area. This would be incredibly slow in scenarios where the amount of game objects exceeds 500, or even 200. The second solution was to store everything in a 2-d list. The world is partitioned up into cells (a tilemap essentially), where each cell or tile is the same size and is square. Each cell would contain a list of the game objects that are currently occupying it (each game object would be inserted into a cell depending on the center of the object's collision mask). A 2-d list would allow me to take the top-left and bottom-right corners of the viewport and easily grab a rectangular area of the grid containing only the cells containing entities that are in valid range to be updated. This method also solves the problem of collision detection; when I take an entity I can find the cell that it is currently in, then check only against entities in it's cell and the 8 cells around it. One problem with this system however is that it prohibits easy lookup of game objects. One solution I had would be to simultaneously keep a hash table that would contain all the positions of the objects in the 2-d list indexed by the id of said object. The major problem with a 2-d list is that it would need to be rebuilt every single game frame (along with the hash table of object positions), which may be a serious detriment to game speed. Both systems have ups and downs and seem to solve some of each other's problems, however using them both together doesn't seem like the best solution either. If anyone has any thoughts, ideas, suggestions, comments, opinions or solutions on new data structures or better implementations of the existing data structures I have in mind, please post, any and all criticism and help is welcome. Thanks in advance! EDIT: Please don't close the question because it has a bad title, I'm just bad with names!

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• Jump-start Your Mind

  - by João Angelo

  I haven’t written in a while mostly because I’ve spent my time reading what others wrote and today I’m writing purely motivated by what I just finished reading. Mindfire: Big Ideas for Curious Mind by Scott Berkun was such a pleasure to read and ended up igniting parts of my mind which I have to admit were becoming a bit numb that I felt the urge to take some time to first say thank you to the author and then recommend it to all your curious minds out there. Now, go read it… it’s time well spent.

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• How much does it cost to develop an Android application?

  - by raychenon

  Following the same iPhone question. How much can a development team charge for an Android app like the official Twitter Inc ? In general how much amount of time is devoted to build the likes of Google Goggles , Google Skymap, Gmail with server side applications included :) Now if you're a solo developer and proud to show your app. How much time have you spent so far ? What was your background GUI desktop in Java, C#, web developer, started from zero programming experience ? Disclaimer : I've developed Android apps ( 10 000 downloads) on my free time and one commercial to be published. Just to know the amount of efforts needed to catch up :)

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• Becoming an expert vs boredom [closed]

  - by QAH

  I am a college student, and I love to program, period. I code all kinds of things in different kinds of languages. Although I enjoy programming, I have an extremely hard time sticking to one project for a long time. I attribute this shortcoming to my high level of curiosity, exploring different technologies, languages, libraries, etc. What would be best? Should I settle down more and spend time on becoming an expert in one or two programming fields, or should I be more of a jack of all trades, trying out all kinds of new technologies, languages, programming methods, etc.? I'm guessing that somewhere in the middle would be best. I'm always amazed at how many developers are able to create one or two projects, and develop on them for years. What techniques do you guys employ to help you stay focused on a project?

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