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  • A list vs. tuple situation in Python

    - by Alphonse
    Is there a situation where the use of a list leads to an error, and you must use a tuple instead? I know something about the properties of both tuples and lists, but not enough to find out the answer to this question. If the question would be the other way around, it would be that lists can be adjusted but tuples don't.

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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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  • Any difference in compiler behavior for each of these snippets?

    - by HotHead
    Please consider following code: 1. uint16 a = 0x0001; if(a < 0x0002) { // do something } 2. uint16 a = 0x0001; if(a < uint16(0x0002)) { // do something } 3. uint16 a = 0x0001; if(a < static_cast<uint16>(0x0002)) { // do something } 4. uint16 a = 0x0001; uint16 b = 0x0002; if(a < b) { // do something } What compiler does in backgorund and what is the best (and correct) way to do above testing? p.s. sorry, but I couldn't find the better title :) EDIT: values 0x0001 and 0x0002 are only example. There coudl be any 2 byte value instead. Thank you in advance!

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  • Is using the break statement bad practice?

    - by Lchi
    I've been told by professors and peers at my university that using the break statement is bad practice, but through my coursework haven't come up with a great reason why. Those who claim that it is bad say that it's a "get out of jail free card" and that you can always avoid using it. My guesses for why its considered bad would be that you could possibly skip some cleanup code after the break, or similarly exit some control structure in an inconsistent state. Is there any reason why using break is(n't) bad practice?

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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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  • Blogger Template: how to change the color of the border css

    - by Lirik
    Hi, I'm trying to change the borders in the style sheet of the template on my blog, but I've never done anything with css so I'm a little bit at a loss... I want to keep the dark background, but I want to create a small border with a slightly different color around my postings. If my guess is correct, then I should modify some of these definitions: body { background:$bgcolor; margin:0; color:$textcolor; font: x-small "Trebuchet MS", Trebuchet, Verdana, Sans-serif; font-size/* */:/**/small; font-size: /**/small; text-align: center; } a:link { color:$linkcolor; text-decoration:none; } a:visited { color:$visitedlinkcolor; text-decoration:none; } a:hover { color:$titlecolor; text-decoration:underline; } a img { border-width:0; } Here is a pastie with the entire template I'm using: http://pastie.org/932535 Is there a quick way to achieve the desired effect? Your help is appreciated!

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  • Recursive query question - break rows into columns?

    - by Stew
    I have a table "Families", like so FamilyID PersonID Relationship ----------------------------------------------- F001 P001 Son F001 P002 Daughter F001 P003 Father F001 P004 Mother F002 P005 Daughter F002 P006 Mother F003 P007 Son F003 P008 Mother and I need output like FamilyID PersonID Father Mother ------------------------------------------------- F001 P001 P003 P004 F001 P002 P003 P004 F001 P003 F001 P004 F002 P005 P006 F002 P006 F003 P007 P008 F003 P008 In which the PersonID of the Father and Mother for a given PersonID are listed (if applicable) in separate columns. I know this must be a relatively trivial query to write (and therefore to find instructions for), but I can't seem to come up with the right search terms. Searching "SQL recursive queries" has gotten me closest, but I can't quite translate those methods to what I'm trying to do here. I'm trying to learn, so multiple methods are welcome, as is vocabulary I should read up on. Thanks!

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  • More ruby-like solution to this problem?

    - by RaouL
    I am learning ruby and practicing it by solving problems from Project Euler. This is my solution for problem 12. # Project Euler problem: 12 # What is the value of the first triangle number to have over five hundred divisors? require 'prime' triangle_number = ->(num){ (num *(num + 1)) / 2 } factor_count = ->(num) do prime_fac = Prime.prime_division(num) exponents = prime_fac.collect { |item| item.last + 1 } fac_count = exponents.inject(:*) end n = 2 loop do tn = triangle_number.(n) if factor_count.(tn) >= 500 puts tn break end n += 1 end Any improvements that can be made to this piece of code?

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  • How do I use Mercurial?

    - by Derek
    I'm assuming Mercurial is for having an updated website and it archiving the old stuff? Easy to test things and such? My question is, how exactly should I get started and can somebody give me a crash course in using Mercurial and using the following techs below: Notepad++ for coding FTP PHP/MySQL Jquery & other js libraries I use windows and would like to keep things fairly simple. I'm developing 1 website currently and want some kind of CVS system in place. Or should I just stick to my current edit file in notepad++ and upload via ftp method and make a backup copy of everything every once and a while? Any thoughts? EDIT: I'm doing http://bugtracker.gttools.com/public/wiki/bluehost/Mercurial right now in order to try and 'install' it.

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  • What is the typical method to separate connected letters in a word using OCR

    - by Maysam
    I am very new to OCR and almost know nothing about the algorithms used to recognize words. I am just getting familiar to that. Could anybody please advise on the typical method used to recognize and separate individual characters in connected form (I mean in a word where all letters are linked together)? Forget about handwriting, supposing the letters are connected together using a known font, what is the best method to determine each individual character in a word? When characters are written separately there is no problem, but when they are joined together, we should know where every single character starts and ends in order to go to the next step and match them individually with a letter. Is there any known algorithm for that?

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  • Problem with for-loop in python

    - by Protean
    This code is supposed to be able to sort the items in self.array based upon the order of the characters in self.order. The method sort runs properly until the third iteration, unil for some reason the for loop seems to repeat indefinitely. What is going on here? class sorting_class: def __init__(self): self.array = ['ca', 'bd', 'ac', 'ab'] #An array of strings self.arrayt = [] self.globali = 0 self.globalii = 0 self.order = ['a', 'b', 'c', 'd'] #Order of characters self.orderi = 0 self.carry = [] self.leave = [] self.sortedlist = [] def sort(self): for arrayi in self.arrayt: #This should only loop for the number items in self.arrayt. However, the third time this is run it seems to loop indefinitely. print ('run', arrayi) #Shows the problem if self.order[self.orderi] == arrayi[self.globali]: self.carry.append(arrayi) else: if self.globali != 0: self.leave.append(arrayi) def srt(self): self.arrayt = self.array my.sort() #First this runs the first time. while len(self.sortedlist) != len(self.array): if len(self.carry) == 1: self.sortedlist.append(self.carry) self.arrayt = self.leave self.leave = [] self.carry = [] self.globali = 1 self.orderi = 0 my.sort() elif len(self.carry) == 0: if len(self.leave) != 0: #Because nothing matches 'aa' during the second iteration, this code runs the third time" self.arrayt = self.leave self.globali = 1 self.orderi += 1 my.sort() else: self.arrayt = self.array self.globalii += 1 self.orderi = self.globalii self.globali = 0 my.sort() self.orderi = 0 else: #This is what runs the second time. self.arrayt = self.carry self.carry = [] self.globali += 1 my.sort() my = sorting_class() my.srt()

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  • Asp.net webservices

    - by Patel
    Hi everyone, I am new to asp.net .. i want to learn about web services.. can anyone pls provide me a good link or pdf on web services for reading it from basic.. thanks in advance..

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  • how to send an array of bytes over a TCP connection (java programming)

    - by Mark Roberts
    Can somebody demonstrate how to send an array of bytes over a TCP connection from a sender program to a receiver program in Java. (I'm new to Java programming, and can't seem to find an example of how to do this that shows both ends of the connection (sender and receiver.) If you know of an existing example, maybe you could post the link. (No need to reinvent the wheel.) P.S. This is NOT homework! :-)

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  • Efficient way in Python to add an element to a comma-separated string

    - by ensnare
    I'm looking for the most efficient way to add an element to a comma-separated string while maintaining alphabetical order for the words: For example: string = 'Apples, Bananas, Grapes, Oranges' addition = 'Cherries' result = 'Apples, Bananas, Cherries, Grapes, Oranges' Also, a way to do this but while maintaining IDs: string = '1:Apples, 4:Bananas, 6:Grapes, 23:Oranges' addition = '62:Cherries' result = '1:Apples, 4:Bananas, 62:Cherries, 6:Grapes, 23:Oranges' Sample code is greatly appreciated. Thank you so much.

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  • Calling button in Action Script 3.0

    - by Meko
    I am trying to make button panel. each button have two type btn_home and btn_home_white I am trying to reach those buttons.It is work if I write for each button their own methods like btn_home.addEventListener(MouseEvent.MOUSE_OVER,overEffect); btn_home_white.addEventListener(MouseEvent.MOUSE_OUT,outEffect); function overEffect(e:MouseEvent) { var myTweenHight:Tween = new Tween( btn_home,"height",Bounce.easeOut,25,0,3,true); var myTweenHight2:Tween = new Tween(btn_home_white,"height",Bounce.easeOut,0,25,3,true); var myTweenAlpha:Tween = new Tween(btn_home_white,"alpha",Strong.easeOut,0,1,2,true); } function outEffect(e:MouseEvent) { var myTweenHight:Tween = new Tween btn_home,"height",Bounce.easeOut,0,25,3,true); var myTweenHight2:Tween = new Tween(btn_home_white,"height",Bounce.easeOut,25,0,3,true); var myTweenAlpha:Tween = new Tween(btn_home_white,"alpha",Strong.easeOut,1,0,2,true); } But I have 10 buttons as btn_buttonname and btn_buttonname_white . I tryed to create Event listener on stage for all.It works for firts type buttons btn_buttonname but How can I get second type buttons? I tryed e.target["_white"] but it does not work . stage.addEventListener(MouseEvent.MOUSE_OVER , overEffect); stage.addEventListener(MouseEvent.MOUSE_OUT , outEffect); function overEffect(e:MouseEvent) { var myTweenHight:Tween = new Tween(e.target,"height",Bounce.easeOut,25,0,3,true); trace("height"); var myTweenHight2:Tween = new Tween(e.target["_white"],"height",Bounce.easeOut,0,25,3,true); var myTweenAlpha:Tween = new Tween(e.target["_white"],"alpha",Strong.easeOut,0,1,2,true); } function outEffect(e:MouseEvent) { var myTweenHight:Tween = new Tween(e.target,"height",Bounce.easeOut,0,25,3,true); var myTweenHight2:Tween = new Tween(e.target["_white"],"height",Bounce.easeOut,25,0,3,true); var myTweenAlpha:Tween = new Tween(e.target["_white"],"alpha",Strong.easeOut,1,0,2,true); }

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  • Condensing multiple else if statements, referencing them from a table?

    - by Haskella
    Hi I'm about to type some 500 else if statements into my code (PHP) which have the exact same coding each: if (color=White); rgb = 255-255-255; print rgb; else if (color=Black); rgb = 0-0-0; print rgb; else if (color=Red); rgb = 255-0-0; print rgb; else if (color=Blue); rgb = 0-0-255; print rgb; [the list keeps going] I also (luckily) have a table that displays the color in the first column and rgb value in the next column for 500 of them... how do I use this to save time typing all those else if statements? Some how I have to reference the table file (made in excel, I'm guessing I'll have to save it as .csv?)

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  • Getting unpredictable data into a tabular format

    - by Acorn
    The situation: Each page I scrape has <input> elements with a title= and a value= I don't know what is going to be on the page. I want to have all my collected data in a single table at the end, with a column for each title. So basically, I need each row of data to line up with all the others, and if a row doesn't have a certain element, then it should be blank (but there must be something there to keep the alignment). eg. First page has: {animal: cat, colour: blue, fruit: lemon, day: monday} Second page has: {animal: fish, colour: green, day: saturday} Third page has: {animal: dog, number: 10, colour: yellow, fruit: mango, day: tuesday} Then my resulting table should be: animal | number | colour | fruit | day cat | none | blue | lemon | monday fish | none | green | none | saturday dog | 10 | yellow | mango | tuesday Although it would be good to keep the order of the title value pairs, which I know dictionaries wont do. So basically, I need to generate columns from all the titles (kept in order but somehow merged together) What would be the best way of going about this without knowing all the possible titles and explicitly specifying an order for the values to be put in?

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  • Form to sort an index in rails

    - by shmichael
    I'm a newcomer to Rails. I want to build a simple form that determines the sort order of a list. I've implemented a form in the likes of - <%= radio_button_tag :sort, "rating" %> <%= label_tag :sort_rating, "order by rating" %> <%= radio_button_tag :sort, "name" %> <%= label_tag :sort_name, "order by name" %> And now I am unsure how to implement the sort at the controller/model level. The aspects I am puzzled about are: Where should the sort be performed How could the sort parameter be persisted How could the code be reused Right now, I can't even get the selected sort method to remain selected after a submit. I would most appreciate any guidance or reference to an example.

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