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  • Can I do a reduce on a list comprehension into two lists, based on two values?

    - by pdknsk
    I've got the following code. sum_review = reduce(add,[book['rw'] for book in books]) sum_rating = reduce(add,[book['rg'] for book in books]) items = len(books) avg_review = sum_review/items avg_rating = sum_rating/items What I'd like is this. sum_review,sum_rating = reduce(add,([book['rw'],[book['rg']) for book in books]) items = len(books) avg_review = sum_review/items avg_rating = sum_rating/items Obviously this doesn't work. How can I solve this redundancy, without a regular loop?

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  • How to break a list into chunks based on some property?

    - by CurlyFro
    public class InvestorMailing { public string To { get; set; } public IEnumerable<string> Attachments { get; set; } public int AttachmentCount { get; set; } public long AttachmentSize { get; set; } } i have an IList<InvestorMailing> mailingList. if the attachment size is greater than x, then i need to split my list and break it into chunks. is there an easy linq-y way to do this?

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  • Are programming languages and methods ineffective? (assembler and C knowledge needed)

    - by b-gen-jack-o-neill
    Hi, for a long time, I am thinking and studying output of C language compiler in asemlber form, as well as CPU architecture. I know this may be silly to you, but it seems to me that something is very ineffective. Please, don´t be angry if I am wrong, and there is some reason I do not see for all these principles. I will be very glad if you tell me why is it designed this way. I actually trully believe I am wrong, I know the genius minds of people which get PCs together knew a reason to do so. What exactly, do you ask? I´ll tell you right away, I use C as a example: 1, Stack local scope memory allocation: So, typical local memory allocation uses stack. Just copy esp to ebp and than allocate all the memory via ebp. OK, I would understand this if you explicitly need allocate RAM by default stack values, but if I do understand it correctly, modern OS use paging as a translation layer between application and physical RAM, when adress you desire is further translated before reaching actuall RAM byte. So why don´t just say 0x00000000 is int a,0x00000004 is int b and so? And access them just by mov 0x00000000,#10? Becouse you wont actually access memory blocks 0x00000000 and 0x00000004 but those your OS set the paging tables to. Actually, since memory allocation by ebp and esp use indirect adressing, "my" way would be even faster. 2, Variable allocation duplicitly: When you run aaplication, Loader load its code into RAM. When you create variable, or string, compiler generates code that pushes these values on the top o stack when created in main. So there is actuall instruction for do so, and that actuall number in memory. So, there are 2 entries of the same value in RAM. One in fomr of instruction, second in form of actuall bytes in the RAM. But why? Why not to just when declaring variable count at which memory block it would be, than when used, just insert this memory location?

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  • Function to register functions to be called if event invoked.

    - by zaidwaqi
    Hi, I have a Panel which contains 20 PictureBox controls. If a user clicks on any of the controls, I want a method within the Panel to be called. How do I do this? public class MyPanel : Panel { public MyPanel() { for(int i = 0; i < 20; i++) { Controls.Add(new PictureBox()); } } // DOESN'T WORK. // function to register functions to be called if the pictureboxes are clicked. public void RegisterFunction( <function pointer> func ) { foreach ( Control c in Controls ) { c.Click += new EventHandler( func ); } } } How do I implement RegisterFunction()? Also, if there are cool C# features that can make the code more elegant, please share. Thanks.

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  • Are python list comprehensions always a good programming practice?

    - by dln385
    To make the question clear, I'll use a specific example. I have a list of college courses, and each course has a few fields (all of which are strings). The user gives me a string of search terms, and I return a list of courses that match all of the search terms. This can be done in a single list comprehension or a few nested for loops. Here's the implementation. First, the Course class: class Course: def __init__(self, date, title, instructor, ID, description, instructorDescription, *args): self.date = date self.title = title self.instructor = instructor self.ID = ID self.description = description self.instructorDescription = instructorDescription self.misc = args Every field is a string, except misc, which is a list of strings. Here's the search as a single list comprehension. courses is the list of courses, and query is the string of search terms, for example "history project". def searchCourses(courses, query): terms = query.lower().strip().split() return tuple(course for course in courses if all( term in course.date.lower() or term in course.title.lower() or term in course.instructor.lower() or term in course.ID.lower() or term in course.description.lower() or term in course.instructorDescription.lower() or any(term in item.lower() for item in course.misc) for term in terms)) You'll notice that a complex list comprehension is difficult to read. I implemented the same logic as nested for loops, and created this alternative: def searchCourses2(courses, query): terms = query.lower().strip().split() results = [] for course in courses: for term in terms: if (term in course.date.lower() or term in course.title.lower() or term in course.instructor.lower() or term in course.ID.lower() or term in course.description.lower() or term in course.instructorDescription.lower()): break for item in course.misc: if term in item.lower(): break else: continue break else: continue results.append(course) return tuple(results) That logic can be hard to follow too. I have verified that both methods return the correct results. Both methods are nearly equivalent in speed, except in some cases. I ran some tests with timeit, and found that the former is three times faster when the user searches for multiple uncommon terms, while the latter is three times faster when the user searches for multiple common terms. Still, this is not a big enough difference to make me worry. So my question is this: which is better? Are list comprehensions always the way to go, or should complicated statements be handled with nested for loops? Or is there a better solution altogether?

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  • What is this type of programming called (creating an online network)?

    - by Byron S
    For practice purposes, I am looking to build an application that is capable of connecting multiple devices through the internet. It will be similar to craigslist, but I want to make this as an iOS application. I have very little experience with web services, as the most I've done is pulled an RSS feed onto the screen. How are these things normally done? If it's similar to a message board, is it as simple as having a database in a server/cloud, and giving all users access to it? Or is it more complicated than that? How should I begin to learn more about the backend? What kind of services are usually used in this kind of thing? The only database I've used is Core Data.

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  • Getting records from a table based on a filter field and Between but also having the OR login for mu

    - by Pentium10
    I have a this table, where I store multiple ids and an age range (def1,def2) CREATE TABLE "template_requirements" ("_id" INTEGER NOT NULL, "templateid" INTEGER, "def1" VARCHAR(255), "def2" VARCHAR(255), PRIMARY KEY("_id")) Having values such as: templateid | def1 | def2 100 | 7 | 25 200 | 40 | 90 300 | 7 | 25 300 | 40 | 60 as you see for templateid 300 we have an or logic: age between 7 and 25 or age between 40 and 60. I want to get all the template ids that are not for a certain age like 25... What's the problem? If I run a query like this one: SELECT group_concat(templateid) FROM template_requirements where and '25' not between cast(def1 as integer) and cast(def2 as integer) it returns 200, 300, which is wrong, as the 300 matched on row 40 to 60, but shouldn't be included in the result as we have a condition with same templateid 7 to 25 that fails the not beetween stuff. How would be the correct query in SQLite, I would like to keep the group_concat stuff.

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  • How exactly can Python compliment your C# skills for windows based development?

    - by JL
    I'm looking for a fun challenge, and am thinking about learning Python. I've heard really good things about the language. My question is, how (if at all) can Python compliment the skills of a typical C# developer working mainly with MS technologies on a Windows Platform. Some examples of typical C# dev on windows would be (SOA applications, web applications, windows services, automation, xml handling) Surely there must be some scenarios where knowing Python would help you get certain tasks done quicker or more efficiently than using traditional C# / MS technologies. If you know of any specific scenarios, then please share. And lastly should this question be a community wiki?

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  • How to check that this event would occur after DOM is ready in jquery ?

    - by Rachel
    I want to get page_tag information from the page and want to make sure that DOM for this page is already ready before getting the page tag information. I am doing $(document).ready( { alert("test"); var page_tag : $("head meta[name='page_tag']").attr('content'); page_tag : (page_tag) ? page_tag : ''; } But it gives me errors, missing : after property id alert("Check if document is ready");\n Any suggestions on what could be the possible reasons for it or any other way of checking if the dom is ready or not before getting page_tag information.

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  • php, js - echoing a number based on how many children there are?

    - by benbyford
    Creating a site in with FrogCMS and using alot of jquery to create an all in one screen site. having trouble in php echoing a number for the number of children for a subject in the database which i can then use as a var in js. some things ive tried, but im not really a developer so having issues here is some code frog supplies to show to utilise articles for example, and articles then has childen in the database. find('/articles/'); ? children(array('limit' = 1, 'order' = 'page.created_on DESC')); ? but im not sure how to create a discrete number to use with the jquery concerning the number of children?? thanks

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  • Android: how to start a service at boot based on user-settings?

    - by Cicerone Cojocaru
    Hey everyone, I'm trying to write an app that consists of an activity that manages a background service. However, I want to implement a user setting for automatically starting the service up at boot time. I have user settings implemented with SharedPreferences and I have the services starting up at boot by using a BroadcastReceiver and listening for BOOT_COMPLETED. However, I can't figure out a good way to implement a setting so that the service is only started at boot if said setting is enabled. I can think of a few cheap ways to do this (such as messing with onCreate() in the service, or creating/checking for a file on SD card) but I want to follow good practice. There must be a good way to do this because there's tons of apps out there that do it, I just can't find anything online about how to do it. Thanks

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  • Excel macro, to copy and paste a cell value based on another cell value?

    - by Keziah Dorman
    Hi I shall try to explain clearly what I need to be able to do, here goes: I have an Excel spread sheet 1 with postcodes in column a and a number in column b. I need to create a macro/formula so that it will see the number (i.e 4) and copy and paste the postcode that number of times into sheet 2 column a underneath each other. I need to do this for the next row down etc until it comes to a blank. Sheet 1 A,B DE43PP,3 DE43PQ,8 Sheet 2 A,B DE43PP, DE43PP, DE43PP, Thanks

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  • What good programming practices will change with C++0x?

    - by Jon
    For example, "Don't return objects by value if they are expensive to copy" (RVO can't always be used). This advice might change because of rvalue references. The same might be said about storing collections of pointers to objects, because copying them by value into the collection was too expensive; this reason might no longer be valid. Or the use of enums might be discouraged in favour of "enum class". What other practices or tips will change?

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  • How to match words as if in a dictionary, based on len-1 or len+1? Python

    - by pearbear
    If I have a word 'raqd', how would I use python to have a spellcheck, so to speak, to find the word 'rad' as an option in 'spellcheck'? What I've been trying to do is this: def isbettermatch(keysplit, searchword): i = 0 trues = 0 falses = 0 lensearchwords = len(searchword) keysplits = copy.deepcopy(keysplit) searchwords = copy.deepcopy(searchword) #print keysplit, searchwords if len(keysplits) == len(searchwords)-1: i = 0 while i < len(keysplits): j = 0 while j < lensearchwords: if keysplits[i] == searchwords[j]: trues +=1 searchwords.pop(j) lensearchwords = len(searchwords) elif keysplits[i] != searchwords[j]: falses +=1 j +=1 i +=1 if trues >= len(searchwords)-1: #print "-------------------------------------------------------", keysplits return True keysplit is a list like ['s', 'p', 'o', 'i', 'l'] for example, and the searchword would be a list ['r', 'a', 'q', 'd']. If the function returns True, then it would print the keyword that matches. Ex. 'rad', for the searchword 'raqd'. I need to find all possible matches for the searchword with a single letter addition or deletion. so ex. 'raqd' would have an option to be 'rad', and 'poted' could be 'posted' or 'potted'. Above is what I have tried, but it is not working well at all. Help much appreciated!

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  • How to restore data on Power Failure using C++ programming on windows.

    - by Tarun
    Hi, In my program I am writing a file of my programs states. I am writing the file many times to the file during the program run, because the program changes some variables that that i need to store very frequently. Now, if , for some reasons my power fails. Then most of the time I loose data in that file. Please, tell me any mechanism which can protect data even if the power fails. (I have written C++ program on windows). Thank you

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  • How long people take to learn a new programming language?

    - by Cawas
    In general aspects, this might be a good reference for everyone. Having an idea of how long people take in average for properly learning how to code can give a very good idea on how dense or long is the path. Someone who never programmed should take weeks or months, even years maybe while someone who's already experienced in the area and know at least 2 different languages might take days, hours or even minutes to start coding. But other than being able to write code that runs, there are ways to write the same program, and it's much harder to get deep knowledge on that than actually being able to program. And sometimes languages differ a lot from one to another on that aspect as well. For instance, we should never have to worry with code-injection in JavaScript like we do in C. So, is there any place we can see some good numbers for how long it takes to learn a language, maybe divided into level of knowledge categories, languages and paradigms, etc?

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