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  • Can I create class properties during __new__ or __init__?

    - by 007brendan
    I want to do something like this. The _print_attr function is designed to be called lazily, so I don't want to evaluate it in the init and set the value to attr. I would like to make attr a property that computes _print_attr only when accessed: class Base(object): def __init__(self): for attr in self._edl_uniform_attrs: setattr(self, attr, property(lambda self: self._print_attr(attr))) def _print_attr(self, attr): print attr class Child(Base): _edl_uniform_attrs = ['foo', 'bar'] me = Child() me.foo me.bar #output: #"foo" #"bar"

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  • extract/slice/reorder lists in (emacs) lisp?

    - by Stephen
    In python, you might do something like i = (0, 3, 2) x = [x+1 for x in range(0,5)] operator.itemgetter(*i)(x) to get (1, 4, 3). In (emacs) lisp, I wrote this function called extract which does something similar, (defun extract (elems seq) (mapcar (lambda (x) (nth x seq)) elems)) (extract '(0 3 2) (number-sequence 1 5)) but I feel like there should be something built in? All I know is first, last, rest, nth, car, cdr... What's the way to go? ~ Thanks in advance ~

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  • Big, Thick Reference Books (PHP / MySQL / Unix) [closed]

    - by Josh K
    I'm looking for in-depth reference books / guides in PHP, MySQL, and Unix. I'm aware there other other questions pertaining to good books for short references of function names, or detailed beginner guides to these systems. I'm looking for something different. I want a book that I can either use as a quick but in-depth (decent write up, not a pocket reference guide) reference to common functions (JOINS, string manipulation, Regular Expressions, etc) while also providing a detailed inner workings explanation on the system itself.

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  • Ternary operator in if-statement?

    - by Pindatjuh
    I've written the following if-statement in Java: if(methodName.equals("set" + this.name) || isBoolean() ? methodName.equals("is" + this.name) : methodName.equals("get" + this.name)) { ... } Is this a good practice to write such expressions in if, to separate state from condition? And can this expression be simplified?

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  • Is OOP based on any branch of mathematics?

    - by ektrules
    I know relational databases are based on set-theory, functional programming is based on lambda calculus, logic programming is based on logic (of course :)), and now that I think of it; I'm not sure if imperative and generic programming is based on any particular branch of mathematics either.

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  • Passing URL as parameter using mod_rewrite

    - by Dusan
    I would like to rewrite dynamic URL /index.php?pid=login&redirect=/previous-page.html to something like this /login.html-r-previous-page.html I tried this RewriteRule ^login.html-r-(.*)$ /index.php?pid=login&redirect=$1 [L] But no succes. I was also trying to change the regex to .+ or some other forms, but it seems useless. Maybe I am making mistake somewhere else. I am new to regular expressions and also mod_rewrite. Thank you for help

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  • Trouble using South with Django and Heroku

    - by Dan
    I had an existing Django project that I've just added South to. I ran syncdb locally. I ran manage.py schemamigration app_name locally I ran manage.py migrate app_name --fake locally I commit and pushed to heroku master I ran syncdb on heroku I ran manage.py schemamigration app_name on heroku I ran manage.py migrate app_name on heroku I then receive this: $ heroku run python notecard/manage.py migrate notecards Running python notecard/manage.py migrate notecards attached to terminal... up, run.1 Running migrations for notecards: - Migrating forwards to 0005_initial. > notecards:0003_initial Traceback (most recent call last): File "notecard/manage.py", line 14, in <module> execute_manager(settings) File "/app/lib/python2.7/site-packages/django/core/management/__init__.py", line 438, in execute_manager utility.execute() File "/app/lib/python2.7/site-packages/django/core/management/__init__.py", line 379, in execute self.fetch_command(subcommand).run_from_argv(self.argv) File "/app/lib/python2.7/site-packages/django/core/management/base.py", line 191, in run_from_argv self.execute(*args, **options.__dict__) File "/app/lib/python2.7/site-packages/django/core/management/base.py", line 220, in execute output = self.handle(*args, **options) File "/app/lib/python2.7/site-packages/south/management/commands/migrate.py", line 105, in handle ignore_ghosts = ignore_ghosts, File "/app/lib/python2.7/site-packages/south/migration/__init__.py", line 191, in migrate_app success = migrator.migrate_many(target, workplan, database) File "/app/lib/python2.7/site-packages/south/migration/migrators.py", line 221, in migrate_many result = migrator.__class__.migrate_many(migrator, target, migrations, database) File "/app/lib/python2.7/site-packages/south/migration/migrators.py", line 292, in migrate_many result = self.migrate(migration, database) File "/app/lib/python2.7/site-packages/south/migration/migrators.py", line 125, in migrate result = self.run(migration) File "/app/lib/python2.7/site-packages/south/migration/migrators.py", line 99, in run return self.run_migration(migration) File "/app/lib/python2.7/site-packages/south/migration/migrators.py", line 81, in run_migration migration_function() File "/app/lib/python2.7/site-packages/south/migration/migrators.py", line 57, in <lambda> return (lambda: direction(orm)) File "/app/notecard/notecards/migrations/0003_initial.py", line 15, in forwards ('user', self.gf('django.db.models.fields.related.ForeignKey')(to=orm['auth.User'])), File "/app/lib/python2.7/site-packages/south/db/generic.py", line 226, in create_table ', '.join([col for col in columns if col]), File "/app/lib/python2.7/site-packages/south/db/generic.py", line 150, in execute cursor.execute(sql, params) File "/app/lib/python2.7/site-packages/django/db/backends/util.py", line 34, in execute return self.cursor.execute(sql, params) File "/app/lib/python2.7/site-packages/django/db/backends/postgresql_psycopg2/base.py", line 44, in execute return self.cursor.execute(query, args) django.db.utils.DatabaseError: relation "notecards_semester" already exists I have 3 models. Section, Semester, and Notecards. I've added one field to the Notecards model and I cannot get it added on Heroku. Thank you.

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  • django sort by manytomany relationship

    - by Marconi
    I have the following model: class Service(models.Model): ratings = models.ManyToManyField(User) Now if I wanna get all the service with ratings sorted in descending order I did something: services_list = Service.objects.filter(ratings__gt=0).distinct() services_list = list(services_list) services_list.sort(key=lambda service: service.ratings.all().count(), reverse=True) As you can see its a three step process and I don't feel right about this. Anybody who knows a better way to do this?

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  • Sorting Python list based on the length of the string

    - by prosseek
    I want to sort a list of strings based on the string length. I tried to use sort as follows, but it doesn't seem to give me correct result. xs = ['dddd','a','bb','ccc'] print xs xs.sort(lambda x,y: len(x) < len(y)) print xs ['dddd', 'a', 'bb', 'ccc'] ['dddd', 'a', 'bb', 'ccc'] What might be wrong?

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  • LINQ problem on remote machine

    - by HaMMeR
    I am using LINQ expressions in my code like this var obj = Collection.Single(collection = (collection.ShortName.Equals("AAA"))); The problem is that this line works fine for me, no problems. But when I upload the same executable to some remote machine with same 32 bit Windows XP. The code execution is just stopping at this line of source. Can anyone help me.

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  • Get string value from http response with Mechanize

    - by Gearóid
    Hi, I'm currently integrating facebook into my current app and I've succeeded in retrieving the access_token using the following code: url="#{url}?#{client_id}&#{client_secret}&#{code}&#{redirect_uri}&type=client_cred" agent = Mechanize.new page = agent.get(url) The page object above has a body which contains text something along the lines of access_token=XXXXX I just want to pull out the access_token value. I can get the entire string simply by writing: page.body But I was wondering is there a way to get the access_token value without resorting to regular expressions etc? Thanks.

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  • php Dollar amount Regular Expression

    - by Thildemar
    I am have completed javascript validation of a form using Regular Expressions and am now working on redundant verification server-side using PHP. I have copied this regular expression from my jscript code that finds dollar values, and reformed it to a PHP friendly format: /\$?((\d{1,3}(,\d{3})*)|(\d+))(\.\d{2})?$/ Specifically: if (preg_match("/\$?((\d{1,3}(,\d{3})*)|(\d+))(\.\d{2})?$/", $_POST["cost"])){} While the expression works great in javascript I get : Warning: preg_match() [function.preg-match]: Compilation failed: nothing to repeat at offset 1 when I run it in PHP. Anyone have a clue why this error is coming up?

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  • Connecting slots and events in PyQt4 in a loop

    - by LukaD
    Im trying to build a calculator with PyQt4 and connecting the 'clicked()' signals from the buttons doesn't as expected. Im creating my buttons for the numbers inside a for loop where i try to connect them afterwards. def __init__(self): for i in range(0,10): self._numberButtons += [QPushButton(str(i), self)] self.connect(self._numberButtons[i], SIGNAL('clicked()'), lambda : self._number(i)) def _number(self, x): print(x) When I click on the buttons all of them print out '9'. Why is that so and how can i fix this?

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  • How do you get the host address and port from a System.Net.EndPoint?

    - by cyclotis04
    I'm using a TcpClient passed to me from a TcpListener, and for the life of me I can't figure out a simple way to get the address and port it's connected to. The best I have so far is _client.Client.RemoteEndPoint.ToString(); which returns a string in the form FFFF::FFFF:FFFF:FFF:FFFF%00:0000. I've managed to extract the address and port using Regular Expressions, but this seems like overkill. What am I missing?

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  • Why does ghci say that 1.1 + 1.1 + 1.1 > 3.3 is True?

    - by Frerich Raabe
    I've been going through a Haskell tutorial recently and noticed this behaviour when trying some simple Haskell expressions in the interactive ghci shell: Prelude> 1.1 + 1.1 == 2.2 True Prelude> 1.1 + 1.1 + 1.1 == 3.3 False Prelude> 1.1 + 1.1 + 1.1 > 3.3 True Prelude> 1.1 + 1.1 + 1.1 3.3000000000000003 Does anybody know why that is?

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  • How can I improve the recursion capabilities of my ECMAScript implementation?

    - by ChaosPandion
    After some resent tests I have found my implementation cannot handle very much recursion. Although after I ran a few tests in Firefox I found that this may be more common than I originally thought. I believe the basic problem is that my implementation requires 3 calls to make a function call. The first call is made to a method named Call that makes sure the call is being made to a callable object and gets the value of any arguments that are references. The second call is made to a method named Call which is defined in the ICallable interface. This method creates the new execution context and builds the lambda expression if it has not been created. The final call is made to the lambda that the function object encapsulates. Clearly making a function call is quite heavy but I am sure that with a little bit of tweaking I can make recursion a viable tool when using this implementation. public static object Call(ExecutionContext context, object value, object[] args) { var func = Reference.GetValue(value) as ICallable; if (func == null) { throw new TypeException(); } if (args != null && args.Length > 0) { for (int i = 0; i < args.Length; i++) { args[i] = Reference.GetValue(args[i]); } } var reference = value as Reference; if (reference != null) { if (reference.IsProperty) { return func.Call(reference.Value, args); } else { return func.Call(((EnviromentRecord)reference.Value).ImplicitThisValue(), args); } } return func.Call(Undefined.Value, args); } public object Call(object thisObject, object[] arguments) { var lexicalEnviroment = Scope.NewDeclarativeEnviroment(); var variableEnviroment = Scope.NewDeclarativeEnviroment(); var thisBinding = thisObject ?? Engine.GlobalEnviroment.GlobalObject; var newContext = new ExecutionContext(Engine, lexicalEnviroment, variableEnviroment, thisBinding); Engine.EnterContext(newContext); var result = Function.Value(newContext, arguments); Engine.LeaveContext(); return result; }

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  • Should I invest time in learning Java language these days? (question from a greenhorn)

    - by dave-keiture
    Hi experts, Assuming you've already had a chance to look through the lambda syntax proposed for Java7 (and the other things that have happened with Java, after Oracle has bought Sun + obvious problems in Java Community Process), what do you think is the future of Java language? Should I, as a Java greenhorn, invest time in learning Java language (not talking about the core JVM, which definitely will survive anything, and worth investments), or concentrate on Scala, Groovy, or other hybrid languages on the JVM platform (I've came into Java world from PHP/Ruby). Thanks in advance.

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  • PHP curly string syntax question

    - by zildjohn01
    I'm running PHP 5.3.0. I've found that the curly string syntax only works when the first character of the expression is $. Is there a way to include other types of expressions (function calls, etc)? Trivial example: <?php $x = '05'; echo "{$x}"; // works as expected echo "{intval($x)}"; // hoped for "5", got "{intval(05)}"

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  • C# How do I replace an actual asterisk character (*) in a Regex expression?

    - by fraXis
    Hello, I have a statement: I have a string such as content = "* test *" I want to search and replace it with so when I am done the string contains this: content = "(*) test (*)" My code is: content = Regex.Replace(content, "*", "(*)"); But this causes an error in C# because it thinks that the * is part of the Regular Expressions Syntax. How can I modify this code so it changes all asterisks in my string to (*) instead without causing a runtime error? Thanks.

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  • why the class of subclass is superclass

    - by Raj
    def singleton_class class << self self end end end class Human proc = lambda { puts 'proc says my class is ' + self.name.to_s } singleton_class.instance_eval do define_method(:lab) do proc.call end end end class Developer < Human end Human.lab # class is Human Developer.lab # class is Human ; oops Why Developer.lab is reporting that it is Human ?

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