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  • Concise way to getattr() and use it if not None in Python

    - by MTsoul
    I am finding myself doing the following a bit too often: attr = getattr(obj, 'attr', None) if attr is not None: attr() # Do something, either attr(), or func(attr), or whatever else: # Do something else Is there a more pythonic way of writing that? Is this better? (At least not in performance, IMO.) try: obj.attr() # or whatever except AttributeError: # Do something else

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  • Memory leak appears only when multiprocessing

    - by Sandro
    I am trying to use python's multiprocessing library to hopefully gain some performance. Specifically I am using its map function. Now, for some reason when I swap it out with its single threaded counterpart I don't get any memory leaks over time. But using the multiprocessing version of map causes my memory to go through the roof. For the record I am doing something which can easily hog up loads of memory, but what would the difference be between the two to cause such a stark difference?

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  • java.util.zip - ZipInputStream v.s. ZipFile

    - by lucho
    Hello, community! I have some general questions regarding the java.util.zip library. What we basically do is an import and an export of many small components. Previously these components were imported and exported using a single big file, e.g.: <component-type-a id="1"/> <component-type-a id="2"/> <component-type-a id="N"/> <component-type-b id="1"/> <component-type-b id="2"/> <component-type-b id="N"/> Please note that the order of the components during import is relevant. Now every component should occupy its own file which should be externally versioned, QA-ed, bla, bla. We decided that the output of our export should be a zip file (with all these files in) and the input of our import should be a similar zip file. We do not want to explode the zip in our system. We do not want opening separate streams for each of the small files. My current questions: Q1. May the ZipInputStream guarantee that the zip entries (the little files) will be read in the same order in which they were inserted by our export that uses ZipOutputStream? I assume reading is something like: ZipInputStream zis = new ZipInputStream(new BufferedInputStream(fis)); ZipEntry entry; while((entry = zis.getNextEntry()) != null) { //read from zis until available } I know that the central zip directory is put at the end of the zip file but nevertheless the file entries inside have sequential order. I also know that relying on the order is an ugly idea but I just want to have all the facts in mind. Q2. If I use ZipFile (which I prefer) what is the performance impact of calling getInputStream() hundreds of times? Will it be much slower than the ZipInputStream solution? The zip is opened only once and ZipFile is backed by RandomAccessFile - is this correct? I assume reading is something like: ZipFile zipfile = new ZipFile(argv[0]); Enumeration e = zipfile.entries();//TODO: assure the order of the entries while(e.hasMoreElements()) { entry = (ZipEntry) e.nextElement(); is = zipfile.getInputStream(entry)); } Q3. Are the input streams retrieved from the same ZipFile thread safe (e.g. may I read different entries in different threads simultaneously)? Any performance penalties? Thanks for your answers!

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  • Exploding by Array of Delimiters

    - by JoeC
    Is there any way to explode() using an array of delimiters? PHP Manual: array explode ( string $delimiter , string $string [, int $limit ] ) Instead of using string $delimiter is there any way to use array $delimiter without affecting performance too much?

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  • Recommended textbook for machine-level programming?

    - by Norman Ramsey
    I'm looking at textbooks for an undergraduate course in machine-level programming. If the perfect book existed, this is what it would look like: Uses examples written in C or assembly language, or both. Covers machine-level operations such as two's-complement integer arithmetic, bitwise operations, and floating-point arithmetic. Explains how caches work and how they affect performance. Explains machine instructions or assembly instructions. Bonus if the example assembly language includes x86; triple bonus if it includes x86-64 (aka AMD64). Explains how C values and data structures are represented using hardware registers and memory. Explains how C control structures are translated into assembly language using conditional and unconditional branch instructions. Explains something about procedure calling conventions and how procedure calls are implemented at the machine level. Books I might be interested in would probably have the words "machine organization" or "computer architecture" in the title. Here are some books I'm considering but am not quite happy with: Computer Systems: A Programmer's Perspective by Randy Bryant and Dave O'Hallaron. This is quite a nice book, but it's a book for a broad, shallow course in systems programming, and it contains a great deal of material my students don't need. Also, it is just out in a second edition, which will make it expensive. Computer Organization and Design: The Hardware/Software Interface by Dave Patterson and John Hennessy. This is also a very nice book, but it contains way more information about how the hardware works than my students need. Also, the exercises look boring. Finally, it has a show-stopping bug: it is based very heavily on MIPS hardware and the use of a MIPS simulator. My students need to learn how to use DDD, and I can't see getting this to work on a simulator. Not to mention that I can't see them cross-compiling their code for the simulator, and so on and so forth. Another flaw is that the book mentions the x86 architecture only to sneer at it. I am entirely sympathetic to this point of view, but news flash! You guys lost! Write Great Code Vol I: Understanding the Machine by Randall Hyde. I haven't evaluated this book as thoroughly as the other two. It has a lot of what I need, but the translation from high-level language to assembler is deferred to Volume Two, which has mixed reviews. My students will be annoyed if I make them buy a two-volume series, even if the price of those two volumes is smaller than the price of other books. I would really welcome other suggestions of books that would help students in a class where they are to learn how C-language data structures and code are translated to machine-level data structures and code and where they learn how to think about performance, with an emphasis on the cache.

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  • nokogiri vs hpricot?

    - by roshan
    Which one would you choose? My important attributes are (not in order) Support & Future enhancements Community & general knowledge base (on the Internet) Comprehensive (i.e proven to parse a wide range of *.*ml pages) Performance Memory Footprint (runtime, not the code-base)

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  • PostgreSQL or MS SQL Server?

    - by mmiika
    I'm considering using PostgreSQL with a .Net web app. Basically 3 reasons: Mature Geo Queries Small footprint + Linux Price I'm wondering a bit about tools though, SQL Server Profiler and query plans and performance monitors have been helpful. How is this world with Postgres? Some other things I should consider? Edit: Will most likely use NHibernate as ORM

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  • Is DateTime.ParseExact() faster than DateTime.Parse()

    - by Nassign
    I would like to know if ParseExact is faster than Parse. I think that it should be ParseExact since you already gave the format but I also think all the checking for the Culture info would slow it down. Does microsoft say in any document on performance difference between the two. The format to be used is a generic 'yyyy/MM/dd' format .

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  • What is the need of collection framework in java?

    - by JavaUser
    Hi, What is the need of Collection framework in Java since all the data operations(sorting/adding/deleting) are possible with Arrays and moreover array is suitable for memory consumption and performance is also better compared with Collections. Can anyone point me a real time data oriented example which shows the difference in both(array/Collections) of these implementations. Thx

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  • Edit very large xml files

    - by Matt
    I would like to create a text box which loads xml files and let users edit them. However, I cannot use XmlDocument to load since the files can be very large. I am looking for options to stream/load the xml document in chunks so that I do not get out of memory errors -- at the same time, performance is important too. Could you let me know what would be good options?

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  • WPF: ComboBox Max Items?

    - by Jonathan Allen
    What is the maximum number of items you can put in a WPF ComboBox before it starts suffering serious performance degration? (Assume bare-bones XP business-class computer.) What is the maximum number of items you can put in a WPF ComboBox before a typical user will start complaining?

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  • How to create sleek customized buttons, tables and other views for iPhone/iPad apps?

    - by wgpubs
    I'm looking to know both what can be customized as well as the recommended way to customize some of the major UIView subclasses in the iPhone SDK (in particular UIButton, UITableView/Cell ... but really open to any of the views in the SDK). Any recommended tutorials? Examples? Are there bad practices that can actually hinder performance and/or destablize your app in any way that should be avoided? Thanks

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  • Reasons for Parallel Extensions working slowly

    - by darja
    I am trying to make my calculating application faster by using Parallel Extensions. I am new in it, so I have just replaced the main foreach loop with Parallel.ForEach. But calculating became more slow. What can be common reasons for decreasing performance of parallel extensions? Thanks

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  • Is django orm & templates thread safe?

    - by Piotr Czapla
    I'm using django orm and templates to create a background service that is ran as management command. Do you know if django is thread safe? I'd like to use threads to speed up processing. The processing is blocked by I/O not CPU so I don't care about performance hit caused by GIL.

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  • what is the proper way to do logging in csv file?

    - by user2003548
    i want to log some information of every single request send to a busy http server in a formatted form,use log module would create some thing i don't want to: [I 131104 15:31:29 Sys:34] i think of csv format but i don't know how to customize it,and python got csv module,but read the manual import csv with open('some.csv', 'w', newline='') as f: writer = csv.writer(f) writer.writerows(someiterable) since it would open and close a file each time, i am afraid in this way would slow down the whole server performance, what could i do?

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