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  • python conditional list creation from 2D lists

    - by dls
    Say I've got a list of lists. Say the inner list of three elements in size and looks like this: ['apple', 'fruit', 1.23] The outer list looks like this data = [['apple', 'fruit', 1.23], ['pear', 'fruit', 2.34], ['lettuce', 'vegetable', 3.45]] I want to iterate through the outer list and cull data for a temporary list only in the case that element 1 matches some keyword (aka: 'fruit'). So, if I'm matching fruit, I would end up with this: tempList = [('apple', 1.23), ('pear', 2.34)] This is one way to accomplish this: tempList = [] for i in data: if i[1] == 'fruit': tempList.append(i[0], i[2]) is there some 'Pythonic' way to do this in fewer lines?

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  • Can I turn off implicit Python unicode conversions to find my mixed-strings bugs?

    - by Tal Weiss
    When profiling our code I was surprised to find millions of calls to C:\Python26\lib\encodings\utf_8.py:15(decode) I started debugging and found that across our code base there are many small bugs, usually comparing a string to a unicode or adding a sting and a unicode. Python graciously decodes the strings and performs the following operations in unicode. How kind. But expensive! I am fluent in unicode, having read Joel Spolsky and Dive Into Python... I try to keep our code internals in unicode only. My question - can I turn off this pythonic nice-guy behavior? At least until I find all these bugs and fix them (usually by adding a u'u')? Some of them are extremely hard to find (a variable that is sometimes a string...). Python 2.6.5 (and I can't switch to 3.x).

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  • How should I declare default values for instance variables in Python?

    - by int3
    Should I give my class members default values like this: class Foo: num = 1 or like this? class Foo: def __init__(self): self.num = 1 In this question I discovered that in both cases, bar = Foo() bar.num += 1 is a well-defined operation. I understand that the first method will give me a class variable while the second one will not. However, if I do not require a class variable, but only need to set a default value for my instance variables, are both methods equally good? Or one of them more 'pythonic' than the other? One thing I've noticed is that in the Django tutorial, they use the second method to declare Models. Personally I think the second method is more elegant, but I'd like to know what the 'standard' way is.

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  • Divide numpy array

    - by BandGap
    Hi all I have some data represented in a 1300x1341 matrix. I would like to split this matrix in several pieces (e.g. 9) so that I can loop over and process them. The data needs to stay ordered in the sense that x[0,1] stays below (or above if you like) x[0,0] and besides x[1,1]. Just like if you had imaged the data, you could draw 2 vertical and 2 horizontal lines over the image to illustrate the 9 parts. If I use numpys reshape (eg. matrix.reshape(9,260,745) or any other combination of 9,260,745) it doesn't yield the required structure since the above mentioned ordering is lost... Did I misunderstand the reshape method or can it be done this way? What other pythonic/numpy way is there to do this?

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  • idiomatic way to take groups of n items from a list in Python?

    - by Wang
    Given a list A = [1 2 3 4 5 6] Is there any idiomatic (Pythonic) way to iterate over it as though it were B = [(1, 2) (3, 4) (5, 6)] other than indexing? That feels like a holdover from C: for a1,a2 in [ (A[i], A[i+1]) for i in range(0, len(A), 2) ]: I can't help but feel there should be some clever hack using itertools or slicing or something. (Of course, two at a time is just an example; I'd like a solution that works for any n.) Edit: related http://stackoverflow.com/questions/1162592/iterate-over-a-string-2-or-n-characters-at-a-time-in-python but even the cleanest solution (accepted, using zip) doesn't generalize well to higher n without a list comprehension and *-notation.

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  • Python - List and Loop in one def

    - by Dunwitch
    I'm trying to get the def wfsc_pod1 and wfsc_ip into the same def. I'm not quite sure how to approach the problem. I want wfsc_pod1 to display all the information for name, subnet and gateway. Then wfsc_ip shows the ip addresses below it. I also get a None value when I run it as it. Not sure why. Anything more pythonic is more appreciated. class OutageAddress: subnet = ["255.255.255.0", "255.255.255.1"] # Gateway order is matched with names gateway = ["192.168.1.1", "192.168.1.2", "192.168.1.3", "192.168.1.4", "192.168.1.5", "192.168.1.6", "192.168.1.7", "192.168.1.8", "192.168.1.9"] name = ["LOC1", "LOC2", "LOC3", "LOC4", "LOC5", "LOC6", "LOC7", "LOC8", "LOC9"] def wfsc_pod1(self): wfsc_1 = "%s\t %s\t %s\t" % (network.name[0],network.subnet[0],network.gateway[0]) return wfsc_1 def wfsc_ip(self): for ip in range(100,110): ip = "192.168.1."+str(ip) print ip network = OutageAddress() print network.wfsc_pod1() print network.wfsc_ip()

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  • Python - Is there a better/efficient way to find a node in tree?

    - by Sej P
    I have a node data structure defined as below and was not sure the find_matching_node method is pythonic or efficient. I am not well versed with generators but think there might be better solution using them. Any ideas? class HierarchyNode(): def __init__(self, nodeId): self.nodeId = nodeId self.children = {} # opted for dictionary to help reduce lookup time def addOrGetChild(self, childNode): return self.children.setdefault(childNode.nodeId,childNode) def find_matching_node(self, node): ''' look for the node in the immediate children of the current node. if not found recursively look for it in the children nodes until gone through all nodes ''' matching_node = self.children.get(node.nodeId) if matching_node: return matching_node else: for child in self.children.itervalues(): matching_node = child.find_matching_node(node) if matching_node: return matching_node return None

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  • Python: How can I override one module in a package with a modified version that lives outside the pa

    - by zlovelady
    I would like to update one module in a python package with my own version of the module, with the following conditions: I want my updated module to live outside of the original package (either because I don't have access to the package source, or because I want to keep my local modifications in a separate repo, etc). I want import statements that refer to original package/module to resolve to my local module Here's an example of what I'd like to do using specifics from django, because that's where this problem has arisen for me: Say this is my project structure django/ ... the original, unadulterated django package ... local_django/ conf/ settings.py myproject/ __init__.py myapp/ myfile.py And then in myfile.py # These imports should fetch modules from the original django package from django import models from django.core.urlresolvers import reverse # I would like this following import statement to grab a custom version of settings # that I define in local_django/conf/settings.py from django.conf import settings def foo(): return settings.some_setting Can I do some magic with the __import__ statement in myproject/__init__.py to accomplish this? Is there a more "pythonic" way to achieve this?

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  • Right design to validate attributes of a class instance

    - by systempuntoout
    Having a simple Python class like this: class Spam(object): __init__(self, description, value): self.description = description self.value = value Which is the correct approach to check these constraints: "description cannot be empty" "value must be greater than zero" Should i: 1.validate data before creating spam object ? 2.check data on __init__ method ? 3.create an is_valid method on Spam class and call it with spam.isValid() ? 4.create an is_valid static method on Spam class and call it with Spam.isValid(description, value) ? 5.check data on setters? 6.... Could you recommend a well designed\Pythonic\not verbose (on class with many attributes)\elegant approach?

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  • Inspiration and influence of the else clause of loop statements?

    - by Aristide
    Python offers an optional loop-else clause which is executed if and only if the loop is not terminated by a break. (In other words, the condition fails for a while-loop or the iterator is exhausted for a for-loop.) Does this loop-else construct originate from another language? (Either theoretical or actually implemented.) Has it been taken up in any newer language? Maybe I should ask the former of Guido, but surely he is too busy for such a futile inquiry. ;-) Related discussion and examples: Pythonic ways to use ‘else’ in a for loop

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  • List filtering: list comprehension vs. lambda + filter

    - by Agos
    I happened to find myself having a basic filtering need: I have a list and I have to filter it by an attribute of the items. My code looked like this: list = [i for i in list if i.attribute == value] But then i thought, wouldn't it be better to write it like this? filter(lambda x: x.attribute == value, list) It's more readable, and if needed for performance the lambda could be taken out to gain something. Question is: are there any caveats in using the second way? Any performance difference? Am I missing the Pythonic Way™ entirely and should do it in yet another way (such as using itemgetter instead of the lambda)? Thanks in advance

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  • Parsing a string representing a float *with an exponent* in Python

    - by Lucas
    Hi, I have a large file with numbers in the form of 6,52353753563E-7. So there's an exponent in that string. float() dies on this. While I could write custom code to pre-process the string into something float() can eat, I'm looking for the pythonic way of converting these into a float (something like a format string passed somewhere). I must say I'm surprised float() can't handle strings with such an exponent, this is pretty common stuff. I'm using python 2.6, but 3.1 is an option if need be.

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  • In Python, is it better to use list comprehensions or for-each loops?

    - by froadie
    Which of the following is better to use and why? Method 1: for k, v in os.environ.items() print "%s=%s" % (k, v) Method 2: print "\n".join(["%s=%s" % (k, v) for k,v in os.environ.items()]) I tend to lead towards the first as more understandable, but that might just be because I'm new to Python and list comprehensions are still somewhat foreign to me. Is the second way considered more Pythonic? I'm assuming there's no performance difference, but I may be wrong. What would be the advantages and disadvantages of these 2 techniques? (Code taken from Dive into Python)

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  • String contains all the elements of a list

    - by CSSS
    I am shifting to Python, and am still relatively new to the pythonic approach. I want to write a function that takes a string and a list and returns true if all the elements in the list occur in the string. This seemed fairly simple. However, I am facing some difficulties with it. The code goes something like this: def myfun(str,list): for a in list: if not a in str: return False return True Example : myfun('tomato',['t','o','m','a']) should return true myfun('potato',['t','o','m','a']) should return false myfun('tomato',['t','o','m']) should return true Also, I was hoping if someone could suggest a possible regex approach here. I am trying out my hands on them too.

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  • How to optimize this script

    - by marks34
    I have written the following script. It opens a file, reads each line from it splitting by new line character and deleting first character in line. If line exists it's being added to array. Next each element of array is splitted by whitespace, sorted alphabetically and joined again. Every line is printed because script is fired from console and writes everything to file using standard output. I'd like to optimize this code to be more pythonic. Any ideas ? import sys def main(): filename = sys.argv[1] file = open(filename) arr = [] for line in file: line = line[1:].replace("\n", "") if line: arr.append(line) for line in arr: lines = line.split(" ") lines.sort(key=str.lower) line = ''.join(lines) print line if __name__ == '__main__': main()

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  • Correct approach to validate attributes of an instance of class

    - by systempuntoout
    Having a simple Python class like this: class Spam(object): __init__(self, description, value): self.description = description self.value = value Which is the correct approach to check these constraints: "description cannot be empty" "value must be greater than zero" Should i: 1.validate data before creating spam object ? 2.check data on __init__ method ? 3.create an is_valid method on Spam class and call it with spam.isValid() ? 4.create an is_valid static method on Spam class and call it with Spam.isValid(description, value) ? 5.check data on setters declaration ? 6.... Could you recommend a well designed\Pythonic\not verbose (on class with many attributes)\elegant approach?

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  • Filtering across two ManyToMany fields

    - by KVISH
    I have a User model and an Event model. I have the following for both: class Event(models.Model): ... timestamp = models.DateTimeField() organization_map = models.ManyToManyField(Organization) class User(AuthUser): ... subscribed_orgs = models.ManyToManyField('Organization') I want to find all events that were created in a certain timeframe and find the users who are subscribed to those organizations. I know how to write SQL for this (it's very easy), but whats the pythonic way of doing this using Django ORM? I'm trying as per below: orgs = Organization.objects.all() events = Event.objects.filter(timestamp__gt=min_time) # Min time is the time I want to start from events = events.filter(organization_map__in=orgs) But from there, how do I map to users who have that organization as a subscription? I'm trying to map it like so: users = User.objects.filter(subscribed_orgs__in=...

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  • Verifying SMTP “MAIL FROM:” Matches “From:” Header in DATA

    - by dkovacevic
    Is there ever a legitimate reason for the SMTP “MAIL FROM:” field to not match the “From:” field in the DATA section of a message, besides mailing lists? From http://stackoverflow.com/questions/1750194/smtp-why-does-email-needs-envelope-and-what-does-the-envelope-mean: “But, to continue your snail mail metaphor, most professional letters will contain the sender's and recipient's addresses printed on the letter itself. Those addresses are not necessary for the postman, but are instead a courtesy to the recipient. So it's sensible that email would work the same way.” The problem with this line of logic lies here: “courtesy to the recipient”. Including the “From:” address in an email via SMTP is not a courtesy; it is required if the recipient is to be able to send a reply. From: How to limit the From header to match MAIL FROM in postfix?: “But if you really want to ensure From: and MAIL FROM then you have to apply header_checks so that Return-Path: matches From:” What are the implications of doing this? Mailing lists would obviously be a problem. Are there any other legitimate uses of differing “MAIL FROM:” and “From:” header information?

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  • What's the best way to create a static utility class in python? Is using metaclasses code smell?

    - by rsimp
    Ok so I need to create a bunch of utility classes in python. Normally I would just use a simple module for this but I need to be able to inherit in order to share common code between them. The common code needs to reference the state of the module using it so simple imports wouldn't work well. I don't like singletons, and classes that use the classmethod decorator do not have proper support for python properties. One pattern I see used a lot is creating an internal python class prefixed with an underscore and creating a single instance which is then explicitly imported or set as the module itself. This is also used by fabric to create a common environment object (fabric.api.env). I've realized another way to accomplish this would be with metaclasses. For example: #util.py class MetaFooBase(type): @property def file_path(cls): raise NotImplementedError def inherited_method(cls): print cls.file_path #foo.py from util import * import env class MetaFoo(MetaFooBase): @property def file_path(cls): return env.base_path + "relative/path" def another_class_method(cls): pass class Foo(object): __metaclass__ = MetaFoo #client.py from foo import Foo file_path = Foo.file_path I like this approach better than the first pattern for a few reasons: First, instantiating Foo would be meaningless as it has no attributes or methods, which insures this class acts like a true single interface utility, unlike the first pattern which relies on the underscore convention to dissuade client code from creating more instances of the internal class. Second, sub-classing MetaFoo in a different module wouldn't be as awkward because I wouldn't be importing a class with an underscore which is inherently going against its private naming convention. Third, this seems to be the closest approximation to a static class that exists in python, as all the meta code applies only to the class and not to its instances. This is shown by the common convention of using cls instead of self in the class methods. As well, the base class inherits from type instead of object which would prevent users from trying to use it as a base for other non-static classes. It's implementation as a static class is also apparent when using it by the naming convention Foo, as opposed to foo, which denotes a static class method is being used. As much as I think this is a good fit, I feel that others might feel its not pythonic because its not a sanctioned use for metaclasses which should be avoided 99% of the time. I also find most python devs tend to shy away from metaclasses which might affect code reuse/maintainability. Is this code considered code smell in the python community? I ask because I'm creating a pypi package, and would like to do everything I can to increase adoption.

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  • Is there any functional-like unix shell?

    - by Caruccio
    I'm (really) newbie to functional programming (in fact only had contact with it using python) but seems to be a good approach for some list-intensive tasks in a shell environment. I'd love to do something like this: $ [ git clone $host/$repo for repo in repo1 repo2 repo3 ] Is there any Unix shell with these kind of feature? Or maybe some feature to allow easy shell access (commands, env/vars, readline, etc...) from within python (the idea is to use python's interactive interpreter as a replacement to bash). EDIT: Maybe a comparative example would clarify. Let's say I have a list composed of dir/file: $ FILES=( build/project.rpm build/project.src.rpm ) And I want to do a really simple task: copy all files to dist/ AND install it in the system (it's part of a build process): Using bash: $ cp ${files[*]} dist/ $ cd dist && rpm -Uvh $(for f in ${files[*]}; do basename $f; done)) Using a "pythonic shell" approach (caution: this is imaginary code): $ cp [ os.path.join('dist', os.path.basename(file)) for file in FILES ] 'dist' Can you see the difference ? THAT is what i'm talking about. How can not exits a shell with these kind of stuff build-in yet? It's a real pain to handle lists in shell, even its being a so common task: list of files, list of PIDs, list of everything. And a really, really, important point: using syntax/tools/features everybody already knows: sh and python. IPython seams to be on a good direction, but it's bloated: if var name starts with '$', it does this, if '$$' it does that. It's syntax is not "natural", so many rules and "workarounds" ([ ln.upper() for ln in !ls ] -- syntax error)

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  • Social Technology and the Potential for Organic Business Networks

    - by Michael Snow
    Guest Blog Post by:  Michael Fauscette, IDCThere has been a lot of discussion around the topic of social business, or social enterprise, over the last few years. The concept of applying emerging technologies from the social Web, combined with changes in processes and culture, has the potential to provide benefits across the enterprise over a wide range of operations impacting employees, customers, partners and suppliers. Companies are using social tools to build out enterprise social networks that provide, among other things, a people-centric collaborative and knowledge sharing work environment which over time can breakdown organizational silos. On the outside of the business, social technology is adding new ways to support customers, market to prospects and customers, and even support the sales process. We’re also seeing new ways of connecting partners to the business that increases collaboration and innovation. All of the new "connectivity" is, I think, leading businesses to a business model built around the concept of the network or ecosystem instead of the old "stand-by-yourself" approach. So, if you think about businesses as networks in the context of all of the other technical and cultural change factors that we're seeing in the new information economy, you can start to see that there’s a lot of potential for co-innovation and collaboration that was very difficult to arrange before. This networked business model, or what I've started to call “organic business networks,” is the business model of the information economy.The word “organic” could be confusing, but when I use it in this context, I’m thinking it has similar traits to organic computing. Organic computing is a computing system that is self-optimizing, self-healing, self-configuring, and self-protecting. More broadly, organic models are generally patterns and methods found in living systems used as a metaphor for non-living systems.Applying an organic model, organic business networks are networks that represent the interconnectedness of the emerging information business environment. Organic business networks connect people, data/information, content, and IT systems in a flexible, self-optimizing, self-healing, self-configuring, and self-protecting system. People are the primary nodes of the network, but the other nodes — data, content, and applications/systems — are no less important.A business built around the organic business network business model would incorporate the characteristics of a social business, but go beyond the basics—i.e., use social business as the operational paradigm, but also use organic business networks as the mode of operating the business. The two concepts complement each other: social business is the “what,” and the organic business network is the “how.”An organic business network lets the business work go outside of traditional organizational boundaries and become the continuously adapting implementation of an optimized business strategy. Value creation can move to the optimal point in the network, depending on strategic influencers such as the economy, market dynamics, customer behavior, prospect behavior, partner behavior and needs, supply-chain dynamics, predictive business outcomes, etc.An organic business network driven company is the antithesis of a hierarchical, rigid, reactive, process-constrained, and siloed organization. Instead, the business can adapt to changing conditions, leverage assets effectively, and thrive in a hyper-connected, global competitive, information-driven environment.To hear more on this topic – I’ll be presenting in the next webcast of the Oracle Social Business Thought Leader Webcast Series - “Organic Business Networks: Doing Business in a Hyper-Connected World” this coming Thursday, June 21, 2012, 10:00 AM PDT – Register here

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  • Bowing to User Experience

    As a consumer of geeky news it is hard to check my Google Reader without running into two or three posts about Apples iPad and in particular the changes to the developer guidelines which seemingly restrict developers to using Apples Xcode tool and Objective-C language for iPad apps. One of the alternatives to Objective-C affected, is MonoTouch, an option with some appeal to me as it is based on the Mono implementation of C#. Seemingly restricted is the key word here, as far as I can tell, no official announcement has been made about its fate. For more details around MonoTouch for iPhone OS, check out Miguel de Icazas post: http://tirania.org/blog/archive/2010/Apr-28.html. These restrictions have provoked some outrage as the perception is that Apple is arrogantly restricting developers freedom to create applications as they choose and perhaps unwittingly shortchanging iPhone/iPad users who wont benefit from these now never-to-be-made great applications. Apples response has mostly been to say they are concentrating on providing a certain user experience to their customers, and to do this, they insist everyone uses the tools they approve. Which isnt a surprising line of reasoning given Apple restricts the hardware used and content of the apps already. The vogue term for this approach is curated, as in a benevolent museum director selecting only the finest artifacts for display or a wise gardener arranging the plants in a garden just so. If this is what a curated experience is like it is hard to argue that consumers are not responding. My iPhone is probably the most satisfying piece of technology I own. Coming from the Razr, it really was an revolution in how the form factor, interface and user experience all tied together. While the curated approach reinvented the smart phone genre, it is easy to forget that this is not a new approach for Apple. Macbooks and Macs are Apple hardware that run Apple software. And theyve been successful, but not quite in the same way as the iPhone or iPad (based on early indications). Why not? Well a curated approach can only be wildly successful if the curator a) makes the right choices and b) offers choices that no one else has. Although its advantages are eroding, the iPhone was different from other phones, a unique, focused, touch-centric experience. The iPad is an attempt to define another category of computing. Macs and Macbooks are great devices, but are not fundamentally a different user experience than a PC, you still have windows, file folders, mouse and keyboard, and similar applications. So the big question for Apple is can they hold on to their market advantage, continuing innovating in user experience and stay on top? Or are they going be like Xerox, and the rest of the world says thank you for the windows metaphor, now let me implement that better? It will be exciting to watch, with Android already a viable competitor and Microsoft readying Windows Phone 7. And to close the loop back to the restrictions on developing for iPhone OS. At this point the main target appears to be Adobe and Adobe Flash. Apples calculation is that a) they dont need those developers or b) the developers they want will learn Apples stuff anyway. My guess is that they are correct; that as much as I like the idea of developers having more options, I am not going to buy a competitors product to spite Apple unless that product is just as usable. For a non-technical consumer, I dont know that this conversation even factors into the buying decision. If it did, wed be talking about how Microsoft is trying to retake a slice of market share from the behemoth that is Linux.Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Removing a platform from Configuration Manager

    - by demoncodemonkey
    I have a solution containing C# and C++/CLI projects. There are 3 platforms in my solution: Any CPU Win32 Mixed Platforms I never want to "just build the C# ones" or "just build the C++ ones", I always want to build all projects. So the platforms metaphor is meaningless to me, I'll leave it on Mixed Platforms or whatever as long as they all build. Now VS sometimes automatically switches the current platform to Any CPU (I'm not sure when or why). This means that pressing F7 will only try to build the C# projects, which is obviously no good. So I have to switch back to Mixed Platforms and try again. So how to workaround this irritating problem? I have tried 2 ways: In Configuration Manager, remove Any CPU and Win32 platforms. This worked until I added a new project and Visual Studio very kindly added them back in... :/ In Configuration Manager, check all checkboxes for all projects in all configurations in all platforms. This becomes a nightmare to manage with many projects in the solution. Any other ideas?

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  • Why does the Chrome spacing work in one JS file and not the other?

    - by Matrym
    If you highlight and copy the text in the first paragraph on this page, then paste it into a rich text editor (dreamweaver or gmail in rich text mode), you will see that some of the text is automagically linked. Basically, it works: http://seox.org/link-building-pro.html -- http://seox.org/lbp/old-pretty.js I'm trying to build a second version, but somewhere along the way I broke it. If you go along with the same process on this new url, spacing before and after the link are removed in Chrome: http://seox.org/test.html -- http://seox.org/lbp/lb-core.js Why does the spacing work correctly in the first one, but not in the second? More importantly, how do I fix the second one so that it doesn't bug out? I asked a variation of this question before, and got a helpful and interesting answer, but hopefully I've asked the question with full detail this time around. Thanks in advance for your time! Edit: I've added a bounty to this post, and would greatly appreciate precise instructions on how to fix the bug (rather than general suggestions. To better illustrate the bug, I've copied the gray box (from the second page) below. Note how the spacing is removed before and after the a tags: Link Building 2 is an amazing tool that helps your website visitors share your content, with proper attribution. It connects to email, social sharing sites, eCommerce sites, and is the<a href="http://seox.org/test.html#seo">SEO</a>'s best friend. Think of it as the sneeze in the viral marketing metaphor. <div> <p id="credit"><br /> Read more about<a href="http://seox.org/test.html">Text Citations</a>by<a href="http://seox.org">seox.org</a></p> </div>

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  • How would the 'Model' in a Rails-type webapp be implemented in a functional programming langauge?

    - by ceptorial
    In MVC web development frameworks such as Ruby on Rails, Django, and CakePHP, HTTP requests are routed to controllers, which fetch objects which are usually persisted to a backend database store. These objects represent things like users, blog posts, etc., and often contain logic within their methods for permissions, fetching and/or mutating other objects, validation, etc. These frameworks are all very much object oriented. I've been reading up recently on functional programming and it seems to tout tremendous benefits such as testability, conciseness, modularity, etc. However most of the examples I've seen for functional programming implement trivial functionality like quicksort or the fibonnacci sequence, not complex webapps. I've looked at a few 'functional' web frameworks, and they all seem to implement the view and controller just fine, but largely skip over the whole 'model' and 'persistence' part. (I'm talking more about frameworks like Compojure which are supposed to be purely functional, versus something Lift which conveniently seems to use the OO part of Scala for the model -- but correct me if I'm wrong here.) I haven't seen a good explanation of how functional programming can be used to provide the metaphor that OO programming provides, i.e. tables map to objects, and objects can have methods which provide powerful, encapsulated logic such as permissioning and validation. Also the whole concept of using SQL queries to persist data seems to violate the whole 'side effects' concept. Could someone provide an explanation of how the 'model' layer would be implemented in a functionally programmed web framework?

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