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  • Will this SQL screw up

    - by Joshua
    I'm sure everyone knows the joys of concurrency when it comes to threading. Imagine the following scenario on every page-load on a noobily set up MySQL db: UPDATE stats SET visits = (visits+1) If a thousand users load the page at same time, will the count screw up? is this that table locking/row locking crap? Which one mysql use.

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  • Numpy Matrix keeps giving me an Error,

    - by uberjumper
    Okay this is werid, i keep getting the error, randomly. ValueError: matrix must be 2-dimensional So i tracked it down, and cornered it to basically something like this: a_list = [[(1,100) for _ in range(32)] for _ in range(32)] numpy.matrix(a_list) Whats wrong with this? If i print a_list it is clearly a 2d matrix of tuples, however numpy does not believe so.

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  • Efficiently generate a 16-character, alphanumeric string

    - by ensnare
    I'm looking for a very quick way to generate an alphanumeric unique id for a primary key in a table. Would something like this work? def genKey(): hash = hashlib.md5(RANDOM_NUMBER).digest().encode("base64") alnum_hash = re.sub(r'[^a-zA-Z0-9]', "", hash) return alnum_hash[:16] What would be a good way to generate random numbers? If I base it on microtime, I have to account for the possibility of several calls of genKey() at the same time from different instances. Or is there a better way to do all this? Thanks.

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  • How to reset Scrapy parameters? (always running under same parameters)

    - by Jean Ventura
    I've been running my Scrapy project with a couple of accounts (the project scrapes a especific site that requieres login credentials), but no matter the parameters I set, it always runs with the same ones (same credentials). I'm running under virtualenv. Is there a variable or setting I'm missing? Edit: It seems that this problem is Twisted related. Even when I run: scrapy crawl -a user='user' -a password='pass' -o items.json -t json SpiderName I still get an error saying: ERROR: twisted.internet.error.ReactorNotRestartable And all the information I get, is the last 'succesful' run of the spider.

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  • Sqlalchemy layout with WSGI application

    - by TheDude
    I'm working on writing a small WSGI application using Bottle and SqlAlchemy and am confused on how the "layout" of my application should be in terms of SqlAlchemy. My confusion is with creating engines and sessions. My understanding is that I should only create one engine with the 'create_engine' method. Should I be creating an engine instance in the global namespace in some sort of singleton pattern and creating sessions based off of it? How have you done this in your projects? Any insight would be appreciated. The examples in the documentation dont seem to make this entirely clear (unless I'm missing something obvious). Any thoughts?

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  • Use Regular expression with fileinput

    - by chrissygormley
    Hello, I am trying to replace a variable stored in another file using regular expression. The code I have tried is: r = re.compile(r"self\.uid\s*=\s*('\w{12})'") for line in fileinput.input(['file.py'], inplace=True): print line.replace(r.match(line), sys.argv[1]), The format of the variable in the file is: self.uid = '027FC8EBC2D1' I am trying to pass in a parameter in this format and use regular expression to verify that the sys.argv[1] is correct format and to find the variable stored in this file and replace it with the new variable. Can anyone help. Thanks for the help.

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  • SQLAlchemy introspection of ORM classes/objects

    - by Adam Batkin
    I am looking for a way to introspect SQLAlchemy ORM classes/entities to determine the types and other constraints (like maximum lengths) of an entity's properties. For example, if I have a declarative class: class User(Base): __tablename__ = "USER_TABLE" id = sa.Column(sa.types.Integer, primary_key=True) fullname = sa.Column(sa.types.String(100)) username = sa.Column(sa.types.String(20), nullable=False) password = sa.Column(sa.types.String(20), nullable=False) created_timestamp = sa.Column(sa.types.DateTime, nullable=False) I would want to be able to find out that the 'fullname' field should be a String with a maximum length of 100, and is nullable. And the 'created_timestamp' field is a DateTime and is not nullable.

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  • sqlite3 'database is locked' won't go away with retries

    - by Azarias
    I have a sqlite3 database that is accessed by a few threads (3-4). I am aware of the general limitations of sqlite3 with regards to concurrency as stated http://www.sqlite.org/faq.html#q6 , but I am convinced that is not the problem. All of the threads both read and write from this database. Whenever I do a write, I have the following construct: try: Cursor.execute(q, params) Connection.commit() except sqlite3.IntegrityError: Notify except sqlite3.OperationalError: print sys.exc_info() print("DATABASE LOCKED; sleeping for 3 seconds and trying again") time.sleep(3) Retry On some runs, I won't even hit this block, but when I do, it never comes out of it (keeps retrying, but I keep getting the 'database is locked' error from exc_info. If I understand the reader/writer lock usage correctly, some amount of waiting should help with the contention. What this sounds like is deadlock, but I do not use any transactions in my code, and every SELECT or INSERT is simply a one off. Some threads, however, keep the same connection when they do their operation (which includes a mix of SELECTS and INSERTS and other modifiers). I would appericiate it if you could shade a light on this, and also ways around fixing it (besides using a different database engine.)

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  • SQLAlchemy: who is in charge of the "session"? ( and how to unit-test with sessions )

    - by Nick Perkins
    I need some guidance on how to use session objects with SQLAlchemy, and how to organize Unit Tests of my mapped objects. What I would like to able to do is something like this: thing = BigThing() # mapped object child = thing.new_child() # create and return a related object thing.save() # will also save the child object In order to achieve this, I was thinking of having the BigThing actually add itself ( and it's children ) to the database -- but maybe this not a good idea? One reason to add objects as soon as possible is Automatic id values that are assigned by the database -- the sooner they are available, the fewer problems there are ( right? ) What is the best way to manage session objects? Who is in charge of the session? Should it be created only when required? or saved for a long time? What about Unit Tests for my mapped objects?...how should the session be handled? Is it ever OK to have mapped objects just automatically add themselves to a database? or is that going to lead to trouble?

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  • Matching First Alphanumeric Character skipping (The |An? )

    - by TheLizardKing
    I have a list of artists, albums and tracks that I want to sort using the first letter of their respective name. The issue arrives when I want to ignore "The ", "A ", "An " and other various non-alphanumeric characters (Talking to you "Weird Al" Yankovic and [dialog]). Django has a nice start '^(An?|The) +' but I want to ignore those and a few others of my choice. I am doing this in Django, using a MySQL db with utf8_bin collation. EDIT Well my fault for not mentioning this but the database I am accessing is pretty much ready only. It's created and maintained by Amarok and I can't alter it without a whole mess of issues. That being said the artist table has The Chemical Brothers listed as The Chemical Brothers so I think I am stuck here. It probably will be slow but that's not so much of a concern for me as it's a personal project.

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  • Counting amount of items in Pythons 'for'

    - by Markum
    Kind of hard to explain, but when I run something like this: fruits = ['apple', 'orange', 'banana', 'strawberry', 'kiwi'] for fruit in fruits: print fruit.capitalize() It gives me this, as expected: Apple Orange Banana Strawberry Kiwi How would I edit that code so that it would "count" the amount of times it's performing the for, and print this? 1 Apple 2 Orange 3 Banana 4 Strawberry 5 Kiwi

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  • All minimum spanning trees implementation

    - by russtbarnacle
    I've been looking for an implementation (I'm using networkx library.) that will find all the minimum spanning trees (MST) of an undirected weighted graph. I can only find implementations for Kruskal's Algorithm and Prim's Algorithm both of which will only return a single MST. I've seen papers that address this problem (such as http://fano.ics.uci.edu/cites/Publication/Epp-TR-95-50.html) but my head tends to explode someway through trying to think how to translate it to code. In fact i've not been able to find an implementation in any language!

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  • Unknown syntax error.

    - by matt1024
    Why do I get a syntax error running this code? If I remove the highlighted section (return cards[i]) I get the error highlighting the function call instead. Please help :) def dealcards(): for i in range(len(cards)): cards[i] = '' for j in range(8): cards[i] = cards[i].append(random.randint(0,9) return cards[i] print (dealcards())

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  • Using Range Function

    - by Michael Alexander Riechmann
    My goal is to make a program that takes an input (Battery_Capacity) and ultimately spits out a list of the (New_Battery_Capacity) and the Number of (Cycle) it takes for it ultimately to reach maximum capacity of 80. Cycle = range (160) Charger_Rate = 0.5 * Cycle Battery_Capacity = float(raw_input("Enter Current Capacity:")) New_Battery_Capacity = Battery_Capacity + Charger_Rate if Battery_Capacity < 0: print 'Battery Reading Malfunction (Negative Reading)' elif Battery_Capacity > 80: print 'Battery Reading Malfunction (Overcharged)' elif float(Battery_Capacity) % 0.5 !=0: print 'Battery Malfunction (Charges Only 0.5 Interval)' while Battery_Capacity >= 0 and Battery_Capacity < 80: print New_Battery_Capacity I was wondering why my Cycle = range(160) isn't working in my program?

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  • How to separate comma separeted data from csv file?

    - by Rahul
    I have opened a csv file and I want to sort each string which is comma separeted and are in same line: ex:: file : name,sal,dept tom,10000,it o/p :: each string in string variable I have a file which is already open, so I can not use "open" API, I have to use "csv.reader" which have to read one line at a time.

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  • What could cause Django to start failing its own tests after an OS and Django reinstall?

    - by Macha
    I had to reinstall my OS, and so, I reinstalled django 1.1. Since reinstalling, when I run tests in my app, I get several failures from django.contrib.auth. Logs: http://dpaste.com/178153/ I asked on #django, and no one is too sure what the cause of the errors are. Some of my own code fails its tests, because it's not fully written yet, but that shouldn't cause django to fail it's core tests... I have included django.contrib.admin, which was mentioned as a possible cause.

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  • slicing 2d numpy array

    - by MedicalMath
    I have a 2d numpy array called FilteredOutput that has 2 columns and 10001 rows, though the number of rows is a variable. I am trying to take the 2nd column of FilteredOutput and use it to populate a new 1d numpy array called timeSeriesArray using the following line of code: timeSeriesArray=p.array(FilteredOutput[:,0]) I got this syntax from the following link. But the problem is that I am getting the following error message: TypeError: list indices must be integers, not tuple Can anyone show me the proper syntax for populating the 1d array timeSeriesArray with the contents of the second column of the 2d array FilteredOutput?

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  • How can I load a sql "dump" file into sql alchemy

    - by JudoWill
    I have a large sql dump file ... with multiple CREATE TABLE and INSERT INTO statements. Is there any way to load these all into a SQLAlchemy sqlite database at once. I plan to use the introspected ORM from sqlsoup after I've created the tables. However, when I use the engine.execute() method it complains: sqlite3.Warning: You can only execute one statement at a time. Is there a way to work around this issue. Perhaps splitting the file with a regexp or some kind of parser, but I don't know enough SQL to get all of the cases for the regexp. Any help would be greatly appreciated. Will EDIT: Since this seems important ... The dump file was created with a MySQL database and so it has quite a few commands/syntax that sqlite3 does not understand correctly.

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  • build an API service in Django

    - by Peter
    Hi all, I want to build an API service using Django. A basic workflow goes like this: First, an http request goes to http://mycompany.com/create.py?id=001&callback=http://callback.com. It will create a folder on the server with name 001. Second, if the folder does not exist, it will be created. You get response immediately in XML format. It will look like: <?xml version="1.0" encoding="UTF-8"?> <response> <status> <statusCode>0</statusCode> <message>Success</message> </status> <group id="001"/> </response> Finally, the server will do its job (i.e. creating the folder). After it is done, the server does a callback to the URL provided. Currently, I use return render_to_response('create.xml', {'statusCode': statusCode, 'statusMessage': statusMessage, 'groupId': groupId, }, mimetype = 'text/xml') to send the XML response back. I have an XML template which has statusCode, statusMessage, groupId placeholders. <?xml version="1.0" encoding="UTF-8"?> <response> <status> <statusCode>{{ statusCode }}</statusCode> <message>{{ statusMessage }}</message> </status> {% if not statusCode %} <group id="{{ groupId }}"/> {% endif %} </response> But in this way I have to put step 3 before step 2, because otherwise step 3 will not be executed if it is after return statement. Can somebody give me some suggestions how to do this? Thanks.

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  • Django - foreignkey problem

    - by realshadow
    Hey, Imagine you have this model: class Category(models.Model): node_id = models.IntegerField(primary_key = True) type_id = models.IntegerField(max_length = 20) parent_id = models.IntegerField(max_length = 20) sort_order = models.IntegerField(max_length = 20) name = models.CharField(max_length = 45) lft = models.IntegerField(max_length = 20) rgt = models.IntegerField(max_length = 20) depth = models.IntegerField(max_length = 20) added_on = models.DateTimeField(auto_now = True) updated_on = models.DateTimeField(auto_now = True) status = models.IntegerField(max_length = 20) node = models.ForeignKey(Category_info, verbose_name = 'Category_info', to_field = 'node_id' The important part is the foreignkey. When I try: Category.objects.filter(type_id = type_g.type_id, parent_id = offset, status = 1) I get an error that get returned more than category, which is fine, because it is supposed to return more than one. But I want to filter the results trough another field, which would be type id (from the second Model) Here it is: class Category_info(models.Model): objtree_label_id = models.AutoField(primary_key = True) node_id = models.IntegerField(unique = True) language_id = models.IntegerField() label = models.CharField(max_length = 255) type_id = models.IntegerField() The type_id can be any number from 1 - 5. I am desparately trying to get only one result where the type_id would be number 1. Here is what I want in sql: SELECT n.*, l.* FROM objtree_nodes n JOIN objtree_labels l ON (n.node_id = l.node_id) WHERE n.type_id = 15 AND n.parent_id = 50 AND l.type_id = 1 Any help is GREATLY appreciated. Regards

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