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  • Eventlet or gevent or Stackless + Twisted, Pylons, Django and SQL Alchemy

    - by Khorkrak
    We're using Twisted extensively for apps requiring a great deal of asynchronous io. There are some cases where stuff is cpu bound instead and for that we spawn a pool of processes to do the work and have a system for managing these across multiple servers as well - all done in Twisted. Works great. The problem is that it's hard to bring new team members up to speed. Writing asynchronous code in Twisted requires a near vertical learning curve. It's as if humans just don't think that way naturally. We're considering a mixed approach perhaps. Maybe do the xmlrpc server part and process management in Twisted still but the other stuff in code that at least looks synchronous while not being as such. Then again I like explicit over implicit so hmmm. Anyway onto greenlets - how well does that stuff work? So there's Stackless and as you can see from my Gallentean avatar I'm well aware of the tremendous success in it's use for CCP's flagship EVE Online game first hand. What about Eventlet or gevent? Well for now only Eventlet works with Twisted. However gevent claims to be faster since it's not a pure python implementation it instead uses libevent. It also has fewer idiosyncrasies and defects supposedly. The documentation there is minimal in comparison to Eventlet and it's maintained by 1 guy as far as I can tell. This makes me leery but all great projects start this way so... Then there's PyPy - I haven't even finished reading about that one yet - just saw it in this thread: Drawbacks of Stackless. So confusing - I'm wondering what the heck to do - sounds like Eventlet is probably the best bet but is it really stable enough? Anyone out there have any experience with it? Should we go with Stackless instead as it's been around and is proven technology - just like Twisted is as well - and they do work together nicely. But still I hate having to have a separate version of Python to do this. what to do.... This somewhat obnoxious blog entry hit the nail on the head for me though: Asynchronous IO for Grownups We're stuck using MySQL as well - I never knew how great PostgreSQL was until having had to work on a production OLTP system in MySQL instead - but that's another story. But if that monkey patch thing really works then wow. Just wow.

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  • Unresolved import: models

    - by Timmy O' Tool
    Hi! I'm doing my VERY first project using python/django/eclipse/pydev following this guide http://docs.djangoproject.com/en/dev/intro/tutorial01/ My only addition is the use of Eclipse/pydev. I'm getting many errors related to "Unresolved imports". I can remove the errors using "remove error markers" and my site runs perfect (I can browse it) but I want to get rid definitively of this problem since errors appear again after I removed them. Any ideas?

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  • 'NoneType' object has no attribute 'get' error using SQLAlchemy

    - by Az
    I've been trying to map an object to a database using SQLAlchemy but have run into a snag. Version info if handy: [OS: Mac OSX 10.5.8 | Python: 2.6.4 | SQLAlchemy: 0.5.8] The class I'm going to map: class Student(object): def __init__(self, name, id): self.id = id self.name = name self.preferences = collections.defaultdict(set) self.allocated_project = None self.allocated_rank = 0 def __repr__(self): return str(self) def __str__(self): return "%s %s" %(self.id, self.name) Background: Now, I've got a function that reads in the necessary information from a text database into these objects. The function more or less works and I can easily access the information from the objects. Before the SQLAlchemy code runs, the function will read in the necessary info and store it into the Class. There is a dictionary called students which stores this as such: students = {} students[id] = Student(<all the info from the various "reader" functions>) Afterwards, there is an "allocation" algorithm that will allocate projects to student. It does that well enough. The allocated_project remains as None if a student is unsuccessful in getting a project. SQLAlchemy bit: So after all this happens, I'd like to map my object to a database table. Using the documentation, I've used the following code to only map certain bits. I also begin to create a Session. from sqlalchemy import * from sqlalchemy.orm import * engine = create_engine('sqlite:///:memory:', echo=False) metadata = MetaData() students_table = Table('studs', metadata, Column('id', Integer, primary_key=True), Column('name', String) ) metadata.create_all(engine) mapper(Student, students_table) Session = sessionmaker(bind=engine) sesh = Session() Now after that, I was curious to see if I could print out all the students from my students dictionary. for student in students.itervalues(): print student What do I get but an error: Traceback (most recent call last): File "~/FYP_Tests/FYP_Tests.py", line 140, in <module> print student File "/~FYP_Tests/Parties.py", line 30, in __str__ return "%s %s" %(self.id, self.name) File "/opt/local/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/SQLAlchemy-0.5.8-py2.6.egg/sqlalchemy/orm/attributes.py", line 158, in __get__ return self.impl.get(instance_state(instance), instance_dict(instance)) AttributeError: 'NoneType' object has no attribute 'get' I'm at a loss as to how to resolve this issue, if it is an issue. If more information is required, please ask and I will provide it.

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  • Installing Pycurl on CentOS?

    - by RadiantHex
    Hi folks, I'm finding it to install pycurl on CentOS 5 quite the mission impossible. This is the error I'm getting: >>> import pycurl Traceback (most recent call last): File "<stdin>", line 1, in <module> ImportError: libcurl.so.4: cannot open shared object file: No such file or directory Some help would be beyond amazing. :|

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  • Using fink to install PyODE

    - by None
    I installed fink and ran this command from terminal: sudo apt-get install python-pyode. I found this command on the internet and expected it to work, as I just installed fink. Am I using the wrong name? Is there a different command to use for Mac OS X (10.5)?

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  • Getting the index of the returned max or min item using max()/min() on a list

    - by KevinGriffin
    I'm using Python's max and min functions on lists for a minimax algorithm, and I need the index of the value returned by max() or min(). In other words, I need to know which move produced the max (at a first player's turn) or min (second player) value. for i in range(9): newBoard = currentBoard.newBoardWithMove([i / 3, i % 3], player) if newBoard: temp = minMax(newBoard, depth + 1, not isMinLevel) values.append(temp) if isMinLevel: return min(values) else: return max(values) I need to be able to return the actual index of the min or max value, not just the value.

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  • OperationalError "unable to open database file" processing query results with SQLAlchemy and SQLite3

    - by Peter
    I'm running into this little problem that I hope is just a dumb user error. It looks like some sort of a size limit with a query to a SQLite database. I managed to reproduce the issue with an in-memory DB and a simple script shown below. I can make it work by either reducing the number of records in the DB; or by reducing the size of each record; or by dropping the order_by() call. I am using Python 2.5.5 and SQLAlchemy 0.6.0 in a Cygwin environment. Thanks! #!/usr/bin/python from sqlalchemy.orm import sessionmaker import sqlalchemy import sqlalchemy.orm class Person(object): def __init__(self, name): self.name = name engine = sqlalchemy.create_engine('sqlite:///:memory:') Session = sessionmaker(bind=engine) metadata = sqlalchemy.schema.MetaData(bind=engine) person_table = sqlalchemy.Table('person', metadata, sqlalchemy.Column('id', sqlalchemy.types.Integer, primary_key=True), sqlalchemy.Column('name', sqlalchemy.types.String)) metadata.create_all(engine) sqlalchemy.orm.mapper(Person, person_table) session = Session() session.add_all([Person("012345678901234567890123456789012") for i in range(5000)]) session.commit() persons = session.query(Person).order_by(Person.name).all() print "count =", len(persons) session.close() The all() call to the query result fails with the OperationalError exception: Traceback (most recent call last): File "./stress.py", line 27, in <module> persons = session.query(Person).order_by(Person.name).all() File "/usr/lib/python2.5/site-packages/sqlalchemy/orm/query.py", line 1343, in all return list(self) File "/usr/lib/python2.5/site-packages/sqlalchemy/orm/query.py", line 1451, in __iter__ return self._execute_and_instances(context) File "/usr/lib/python2.5/site-packages/sqlalchemy/orm/query.py", line 1456, in _execute_and_instances mapper=self._mapper_zero_or_none()) File "/usr/lib/python2.5/site-packages/sqlalchemy/orm/session.py", line 737, in execute clause, params or {}) File "/usr/lib/python2.5/site-packages/sqlalchemy/engine/base.py", line 1109, in execute return Connection.executors[c](self, object, multiparams, params) File "/usr/lib/python2.5/site-packages/sqlalchemy/engine/base.py", line 1186, in _execute_clauseelement return self.__execute_context(context) File "/usr/lib/python2.5/site-packages/sqlalchemy/engine/base.py", line 1215, in __execute_context context.parameters[0], context=context) File "/usr/lib/python2.5/site-packages/sqlalchemy/engine/base.py", line 1284, in _cursor_execute self._handle_dbapi_exception(e, statement, parameters, cursor, context) File "/usr/lib/python2.5/site-packages/sqlalchemy/engine/base.py", line 1282, in _cursor_execute self.dialect.do_execute(cursor, statement, parameters, context=context) File "/usr/lib/python2.5/site-packages/sqlalchemy/engine/default.py", line 277, in do_execute cursor.execute(statement, parameters) sqlalchemy.exc.OperationalError: (OperationalError) unable to open database file u'SELECT person.id AS person_id, person.name AS person_name \nFROM person ORDER BY person.name' ()

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  • Node.js as a custom (streaming) upload handler for Django

    - by Gijs
    I want to build an upload-centric app using Django. One way to do this is with nginx's upload module (nonblocking) but it has its problems. Node.js is supposed to be a good candidate for this type of application. But how can I make node.js act as an upload_handler() for Django (http://docs.djangoproject.com/en/1.1/topics/http/file-uploads/#modifying-upload-handlers-on-the-fly) I'm not sure where to look for examples?

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  • Comments in string and strings in comments

    - by Jay Gridley
    Hi there, I am trying to count characters in comments included in C code using Python and Regex, but no success. I can erase strings first to get rid of comments in strings, but this will erase string in comments too and result will be bad ofc. Is there any chance to ask by using regex to not match strings in comments or vice versa?

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  • Django syncdb error

    - by Hulk
    /mysite/project4 class notes(models.Model): created_by = models.ForeignKey(User) detail = models.ForeignKey(Details) Details and User are in the same module i.e,/mysite/project1 In project1 models i have defined class User(): ...... class Details(): ...... When DB i synced there is an error saying Error: One or more models did not validate: project4: Accessor for field 'detail' clashes with related field . Add a related_name argument to the definition for 'detail'. How can this be solved.. thanks..

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  • pyQt4: QWidget subclass not responding to new setStyleSheet() background colour

    - by Ronny
    I am having an issue with PyQt4. I want to create a new widget within a window, and I want this widget to have a custom color. When i create a subclass of the QWidget class, and instantiate it, I am not able to change its background color through the setStyleSheet() function. When I instantiate a new QWidget object, I have no problems in changing its background color. But i dont want an ordinary QWidget object.I want to create my own subclass of QWidget. When i create a subclass of a QPushButton, I am also able to change its background color using the setStyleSheet() function. There are no error messages or warnings in the console window, it just refuses to work properly without any indication as to why. So what i would like to know is why is it that i can change the background color of a widget if i simply create a QWidget object, or a subclass of QPushButton, but not when i create a subclass of QWidget. And how can i therefore change the background color of an object that is a subclass of QWidget? Is it maybe something specific to the version of python or PyQt that i am using? Is it a bug in the library? or some flaw in the way that i am writing my code? I am using python 2.6.4 and PyQt4 Below is an example of the code that leads me to trouble. There are three widgets within the window one below the other. The parent widget is set with background color of green. The top widget is set to red, the middle one, is the subclass of QWidget, which should be blue, but it appears invisible because it takes on the color of the parent window for some reason. and the bottom widget is a subclass of QPushButton and is white. import sys from PyQt4 import QtGui, QtCore ################################################################################ #--------------------------------------------------------- CUSTOM WIDGET CLASS 1 class CustomWidget(QtGui.QWidget): def __init__(self, parent): QtGui.QWidget.__init__(self, parent) # some custom properties and functions will follow ################################################################################ #--------------------------------------------------------- CUSTOM WIDGET CLASS 2 class CustomWidget2(QtGui.QPushButton): def __init__(self, parent): QtGui.QPushButton.__init__(self, parent) # some custom properties and functions will follow ################################################################################ #----------------------------------------------------------- PARENT WIDGET CLASS class Parent(QtGui.QWidget): def __init__(self, parent=None): #---------------------------------------------------------- SETUP WINDOW QtGui.QWidget.__init__(self, parent) self.resize(500, 340) self.setStyleSheet("QWidget {background-color: #00FF00}") #-------------------------------------------------- SETUP DEFAULT WIDGET wid1 = QtGui.QWidget(self) wid1.setGeometry(10, 10, 480, 100) wid1.setStyleSheet("QWidget {background-color: #FF0000 }") #------------------------------------------------- SETUP CUSTOM WIDGET 1 wid2 = CustomWidget(self) wid2.setGeometry(10, 120, 480, 100) wid2.setStyleSheet("QWidget {background-color: #0000FF }") for i in dir(wid2): print i #------------------------------------------------- SETUP CUSTOM WIDGET 2 wid3 = CustomWidget2(self) wid3.setGeometry(10, 230, 480, 100) wid3.setStyleSheet("QWidget {background-color: #FFFFFF }") ################################################################################ #-------------------------------------------------------------------------- MAIN app = QtGui.QApplication(sys.argv) win = Parent() win.show() app.exec_()

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  • How do I use m2crypto to validate a X509 certificate chain in a non-SSL setting

    - by Brock Pytlik
    I'm trying to figure out how to, using m2crypto, validate the chain of trust from a public key version of a X509 certificate back to one of a set of known root CA's when the chain may be arbitrarily long. The SSL.Context module looks promising except that I'm not doing this in the context of a SSL connection and I can't see how the information passed to load_verify_locations is used. Essentially, I'm looking for the interface that's equivalent to: openssl verify pub_key_x509_cert Is there something like that in m2crypto? Thanks.

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  • What's the difference between arguments with default values and keyword-arguments?

    - by o_O Tync
    In Python, what's the difference between arguments having default values: def f(a,b,c=1,d=2): pass and keyword arguments: def f(a=1,b=2,c=3): pass ? I guess there's no difference, but the tutorial has two sections: 4.7.1. Default Argument Values 4.7.2. Keyword Arguments which sounds like there are some difference in them. If so, why can't I use this syntax in 2.6: def pyobj_path(*objs, as_list=False): pass ?

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  • Scripting in Java

    - by eflles
    Me and some friends are writing a MORPG in Java, and we would like to use a scripting language to, eg. to create quests. We have non experience with scripting in Java. We have used Python, but we are very inexperienced with it. One of us also have used Javascript. What scripting language should we use? What scripting language should we not use?

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  • How to run nosetests from netbeans?

    - by Chris089
    I recently started using netbeans for python development and really like it. However, the test runner in netbeans does not run my doctests, nor does it run my test functions written using nose. I always have to switch to the shell and run 'setup.py test' or 'nosetests' manually. Is there a way to integrate this into netbenas 6.8?

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  • How to optimize my PageRank calculation?

    - by asmaier
    In the book Programming Collective Intelligence I found the following function to compute the PageRank: def calculatepagerank(self,iterations=20): # clear out the current PageRank tables self.con.execute("drop table if exists pagerank") self.con.execute("create table pagerank(urlid primary key,score)") self.con.execute("create index prankidx on pagerank(urlid)") # initialize every url with a PageRank of 1.0 self.con.execute("insert into pagerank select rowid,1.0 from urllist") self.dbcommit() for i in range(iterations): print "Iteration %d" % i for (urlid,) in self.con.execute("select rowid from urllist"): pr=0.15 # Loop through all the pages that link to this one for (linker,) in self.con.execute("select distinct fromid from link where toid=%d" % urlid): # Get the PageRank of the linker linkingpr=self.con.execute("select score from pagerank where urlid=%d" % linker).fetchone()[0] # Get the total number of links from the linker linkingcount=self.con.execute("select count(*) from link where fromid=%d" % linker).fetchone()[0] pr+=0.85*(linkingpr/linkingcount) self.con.execute("update pagerank set score=%f where urlid=%d" % (pr,urlid)) self.dbcommit() However, this function is very slow, because of all the SQL queries in every iteration >>> import cProfile >>> cProfile.run("crawler.calculatepagerank()") 2262510 function calls in 136.006 CPU seconds Ordered by: standard name ncalls tottime percall cumtime percall filename:lineno(function) 1 0.000 0.000 136.006 136.006 <string>:1(<module>) 1 20.826 20.826 136.006 136.006 searchengine.py:179(calculatepagerank) 21 0.000 0.000 0.528 0.025 searchengine.py:27(dbcommit) 21 0.528 0.025 0.528 0.025 {method 'commit' of 'sqlite3.Connecti 1 0.000 0.000 0.000 0.000 {method 'disable' of '_lsprof.Profiler 1339864 112.602 0.000 112.602 0.000 {method 'execute' of 'sqlite3.Connec 922600 2.050 0.000 2.050 0.000 {method 'fetchone' of 'sqlite3.Cursor' 1 0.000 0.000 0.000 0.000 {range} So I optimized the function and came up with this: def calculatepagerank2(self,iterations=20): # clear out the current PageRank tables self.con.execute("drop table if exists pagerank") self.con.execute("create table pagerank(urlid primary key,score)") self.con.execute("create index prankidx on pagerank(urlid)") # initialize every url with a PageRank of 1.0 self.con.execute("insert into pagerank select rowid,1.0 from urllist") self.dbcommit() inlinks={} numoutlinks={} pagerank={} for (urlid,) in self.con.execute("select rowid from urllist"): inlinks[urlid]=[] numoutlinks[urlid]=0 # Initialize pagerank vector with 1.0 pagerank[urlid]=1.0 # Loop through all the pages that link to this one for (inlink,) in self.con.execute("select distinct fromid from link where toid=%d" % urlid): inlinks[urlid].append(inlink) # get number of outgoing links from a page numoutlinks[urlid]=self.con.execute("select count(*) from link where fromid=%d" % urlid).fetchone()[0] for i in range(iterations): print "Iteration %d" % i for urlid in pagerank: pr=0.15 for link in inlinks[urlid]: linkpr=pagerank[link] linkcount=numoutlinks[link] pr+=0.85*(linkpr/linkcount) pagerank[urlid]=pr for urlid in pagerank: self.con.execute("update pagerank set score=%f where urlid=%d" % (pagerank[urlid],urlid)) self.dbcommit() This function is 20 times faster (but uses a lot more memory for all the temporary dictionaries) because it avoids the unnecessary SQL queries in every iteration: >>> cProfile.run("crawler.calculatepagerank2()") 64802 function calls in 6.950 CPU seconds Ordered by: standard name ncalls tottime percall cumtime percall filename:lineno(function) 1 0.004 0.004 6.950 6.950 <string>:1(<module>) 1 1.004 1.004 6.946 6.946 searchengine.py:207(calculatepagerank2 2 0.000 0.000 0.104 0.052 searchengine.py:27(dbcommit) 23065 0.012 0.000 0.012 0.000 {meth 'append' of 'list' objects} 2 0.104 0.052 0.104 0.052 {meth 'commit' of 'sqlite3.Connection 1 0.000 0.000 0.000 0.000 {meth 'disable' of '_lsprof.Profiler' 31298 5.809 0.000 5.809 0.000 {meth 'execute' of 'sqlite3.Connectio 10431 0.018 0.000 0.018 0.000 {method 'fetchone' of 'sqlite3.Cursor' 1 0.000 0.000 0.000 0.000 {range} But is it possible to further reduce the number of SQL queries to speed up the function even more?

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  • Distance Between GIS Points

    - by Paul
    I have a large number of GIS (latitude, longitude) coordinates, and I'd like to get the distance between them. Is there a service that will calculate the shortest path for me? I know about google maps, but I'd like something I can use from Python, and that can handle a large batch of requests at once. I'm looking for the driving distance, so a straight distance won't do. Thanks

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  • BasicHTTPServer, SimpleHTTPServer and concurrency

    - by braindump
    I'm writing a small web server for testing purposes using python, BasicHTTPServer and SimpleHTTPServer. It looks like it's processing one request at a time. Is there any way to make it a little faster without messing around too deeply? Basicly my code looks as the following and I'd like to keep it this simple ;) os.chdir(webroot) httpd = BaseHTTPServer.HTTPServer(("", port), SimpleHTTPServer.SimpleHTTPRequestHandler) print("Serving directory %s on port %i" %(webroot, port) ) try: httpd.serve_forever() except KeyboardInterrupt: print("Server stopped.")

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