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  • When to use \A in regex?

    - by S.Mark
    End of line anchor $ match even there is extra trailing \n in matched string, so we use \Z instead of $ For example ^\w+$ will match the string abcd\n but ^\w+\Z is not How about \A and when to use?

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  • How to set a __str__ method for all ctype Structure classes?

    - by Reuben Thomas
    [Since asking this question, I've found: http://www.cs.unc.edu/~gb/blog/2007/02/11/ctypes-tricks/ which gives a good answer.] I just wrote a __str__ method for a ctype-generated Structure class 'foo' thus: def foo_to_str(self): s = [] for i in foo._fields_: s.append('{}: {}'.format(i[0], foo.\_\_getattribute__(self, i[0]))) return '\n'.join(s) foo.\_\_str__ = foo_to_str But this is a fairly natural way to produce a __str__ method for any Structure class. How can I add this method directly to the Structure class, so that all Structure classes generated by ctypes get it? (I am using the h2xml and xml2py scripts to auto-generate ctypes code, and this offers no obvious way to change the names of the classes output, so simply subclassing Structure, Union &c. and adding my __str__ method there would involve post-processing the output of xml2py.)

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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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  • Union on ValuesQuerySet in django

    - by Wuxab
    I've been searching for a way to take the union of querysets in django. From what I read you can use query1 | query2 to take the union... This doesn't seem to work when using values() though. I'd skip using values until after taking the union but I need to use annotate to take the sum of a field and filter on it and since there's no way to do "group by" I have to use values(). The other suggestions I read were to use Q objects but I can't think of a way that would work. Do I pretty much need to just use straight SQL or is there a django way of doing this? What I want is: q1 = mymodel.objects.filter(date__lt = '2010-06-11').values('field1','field2').annotate(volsum=Sum('volume')).exclude(volsum=0) q2 = mymodel.objects.values('field1','field2').annotate(volsum=Sum('volume')).exclude(volsum=0) query = q1|q2 But this doesn't work and as far as I know I need the "values" part because there's no other way for Sum to know how to act since it's a 15 column table.

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  • Django choking oddly on some static media

    - by Edan Maor
    My situation: I'm serving static media via Django on my dev machine. On some files that I try and load, I get back this error: Traceback: File "c:\Program Files\Python26\Lib\site-packages\django\core\handlers\base.py" in get_response 92. response = callback(request, *callback_args, **callback_kwargs) File "E:\Stack2Blog\src.hg\stack2blog\..\stack2blog\stack2blogapp\views.py" in userpage 71. so_user = site.user(userid) File "E:\Stack2Blog\src.hg\stack2blog\..\stack2blog\stack2blogapp\stackexchange.py" in user 476. u, = self.users((nid,), **kw) File "E:\Stack2Blog\src.hg\stack2blog\..\stack2blog\stack2blogapp\stackexchange.py" in users 481. return self._get(User, ids, 'users', kw) File "E:\Stack2Blog\src.hg\stack2blog\..\stack2blog\stack2blogapp\stackexchange.py" in _get 471. return self.build(root, typ, coll, kw) File "E:\Stack2Blog\src.hg\stack2blog\..\stack2blog\stack2blogapp\stackexchange.py" in build 448. json = self._request(url, kw) File "E:\Stack2Blog\src.hg\stack2blog\..\stack2blog\stack2blogapp\stackexchange.py" in _request 422. dump = json.load(data) File "c:\Program Files\Python26\lib\json\__init__.py" in load 264. return loads(fp.read(), Exception Type: AttributeError at /userpage/362498 Exception Value: 'str' object has no attribute 'read' I've traced it to specific files which don't work (by going to their specific urls). Here's the odd part: changing the filename of the files makes them suddenly work. For example, I had a file called 'post.jpg', which gave this error. I renamed it to 'pos.jpg' and it worked. Back to 'post.jpg' and it gives the same error.

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  • how can i set the key 'blob-key' about BlobStore?

    - by pyleaf
    I use the jquery plugin "uploadify" to upload multiple files to My App(GAE), and then save them with blobstore, but it failed. I debug the code into get_uploads, it seems field.type_options is empty and of course has 'blob-key'. Q: where does the key 'blob-key' come from? thank you!

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  • Efficient way to store tuples in the datastore

    - by Drew Sears
    If I have a pair of floats, is it any more efficient (computationally or storage-wise) to store them as a GeoPtProperty than it would be pickle the tuple and store it as a BlobProperty? If GeoPt is doing something more clever to keep multiple values in a single property, can it be leveraged for arbitrary data? Can I store the tuple ("Johnny", 5) in a single entity property in a similarly efficient manner?

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  • Right way to return proxy model instance from a base model instance in Django ?

    - by sotangochips
    Say I have models: class Animal(models.Model): type = models.CharField(max_length=255) class Dog(Animal): def make_sound(self): print "Woof!" class Meta: proxy = True class Cat(Animal): def make_sound(self): print "Meow!" class Meta: proxy = True Let's say I want to do: animals = Animal.objects.all() for animal in animals: animal.make_sound() I want to get back a series of Woofs and Meows. Clearly, I could just define a make_sound in the original model that forks based on animal_type, but then every time I add a new animal type (imagine they're in different apps), I'd have to go in and edit that make_sound function. I'd rather just define proxy models and have them define the behavior themselves. From what I can tell, there's no way of returning mixed Cat or Dog instances, but I figured maybe I could define a "get_proxy_model" method on the main class that returns a cat or a dog model. Surely you could do this, and pass something like the primary key and then just do Cat.objects.get(pk = passed_in_primary_key). But that'd mean doing an extra query for data you already have which seems redundant. Is there any way to turn an animal into a cat or a dog instance in an efficient way? What's the right way to do what I want to achieve?

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  • Setting up relations/mappings for a SQLAlchemy many-to-many database

    - by Brent Ramerth
    I'm new to SQLAlchemy and relational databases, and I'm trying to set up a model for an annotated lexicon. I want to support an arbitrary number of key-value annotations for the words which can be added or removed at runtime. Since there will be a lot of repetition in the names of the keys, I don't want to use this solution directly, although the code is similar. My design has word objects and property objects. The words and properties are stored in separate tables with a property_values table that links the two. Here's the code: from sqlalchemy import Column, Integer, String, Table, create_engine from sqlalchemy import MetaData, ForeignKey from sqlalchemy.orm import relation, mapper, sessionmaker from sqlalchemy.ext.declarative import declarative_base engine = create_engine('sqlite:///test.db', echo=True) meta = MetaData(bind=engine) property_values = Table('property_values', meta, Column('word_id', Integer, ForeignKey('words.id')), Column('property_id', Integer, ForeignKey('properties.id')), Column('value', String(20)) ) words = Table('words', meta, Column('id', Integer, primary_key=True), Column('name', String(20)), Column('freq', Integer) ) properties = Table('properties', meta, Column('id', Integer, primary_key=True), Column('name', String(20), nullable=False, unique=True) ) meta.create_all() class Word(object): def __init__(self, name, freq=1): self.name = name self.freq = freq class Property(object): def __init__(self, name): self.name = name mapper(Property, properties) Now I'd like to be able to do the following: Session = sessionmaker(bind=engine) s = Session() word = Word('foo', 42) word['bar'] = 'yes' # or word.bar = 'yes' ? s.add(word) s.commit() Ideally this should add 1|foo|42 to the words table, add 1|bar to the properties table, and add 1|1|yes to the property_values table. However, I don't have the right mappings and relations in place to make this happen. I get the sense from reading the documentation at http://www.sqlalchemy.org/docs/05/mappers.html#association-pattern that I want to use an association proxy or something of that sort here, but the syntax is unclear to me. I experimented with this: mapper(Word, words, properties={ 'properties': relation(Property, secondary=property_values) }) but this mapper only fills in the foreign key values, and I need to fill in the other value as well. Any assistance would be greatly appreciated.

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  • Is django orm & templates thread safe?

    - by Piotr Czapla
    I'm using django orm and templates to create a background service that is ran as management command. Do you know if django is thread safe? I'd like to use threads to speed up processing. The processing is blocked by I/O not CPU so I don't care about performance hit caused by GIL.

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  • has any tools easy to download or uploaed data from gae ..

    - by zjm1126
    i find this: http://aralbalkan.com/1784 but it is : Gaebar is an easy-to-use, standalone Django application that you can plug in to your existing Google App Engine Django or app-engine-patch-based Django applications on Google App Engine to give them datastore backup and restore functionality. my app is not based on django,so did you know any tools esay to do this . thanks

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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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  • 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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  • How to convert string "0671" or "0x45" into integer form with 0 and 0x in the beginning.

    - by Harshit Sharma
    I wanted to make my own encryption algorithm and decryption algorithm , encryption algorithm works fine and converts ascii value of the characters into alternate hexadecimal and octal representations. But when I tried decryption, problem occured as it return int('0671') = 671, as 0671 is string type in the following code. Is there a method to convert "ox56" into integer form?????? NOTE: Following string is alternate octal and hexa of ascii value of char. ///////////////DECRYPTION/////// l="01630x7401620x6901560x67" f=len(l) k=0 d=0 x=[] for i in range(0,f,4): g=l[i:i+4] print g k=k+1 if(k%2==0): p=g print p else: p=int(g) print p

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  • Rearranging a sequence

    - by sarah
    I'm have trouble rearranging sequences so the amount of letters in the given original sequence are the same in the random generated sequences. For example: If i have a string 'AAAC' I need that string rearranged randomly so the amount of A's and C's are the same.

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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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  • Creating a custom widget using django for use on external sites

    - by ajt
    I have a new site that I am putting together and part of it has statistics for the site's users. I would like to create a widget that others can use on another website by invoking javascript that reads data from my server and shows that statistics for a given user, but I am having a hard time finding specific tutorials that covers this in django. I have seen the link at Alex Maradon's site [0], but it looks to me like that is passing html back to the widget and I am having a hard time figuring out how to do this using something like xml. Are there any django apps for doing this or does anyone know of good how-tos? [0] http://alexmarandon.com/articles/web_widget_jquery/

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  • Non standard interaction among two tables to avoid very large merge

    - by riko
    Suppose I have two tables A and B. Table A has a multi-level index (a, b) and one column (ts). b determines univocally ts. A = pd.DataFrame( [('a', 'x', 4), ('a', 'y', 6), ('a', 'z', 5), ('b', 'x', 4), ('b', 'z', 5), ('c', 'y', 6)], columns=['a', 'b', 'ts']).set_index(['a', 'b']) AA = A.reset_index() Table B is another one-column (ts) table with non-unique index (a). The ts's are sorted "inside" each group, i.e., B.ix[x] is sorted for each x. Moreover, there is always a value in B.ix[x] that is greater than or equal to the values in A. B = pd.DataFrame( dict(a=list('aaaaabbcccccc'), ts=[1, 2, 4, 5, 7, 7, 8, 1, 2, 4, 5, 8, 9])).set_index('a') The semantics in this is that B contains observations of occurrences of an event of type indicated by the index. I would like to find from B the timestamp of the first occurrence of each event type after the timestamp specified in A for each value of b. In other words, I would like to get a table with the same shape of A, that instead of ts contains the "minimum value occurring after ts" as specified by table B. So, my goal would be: C: ('a', 'x') 4 ('a', 'y') 7 ('a', 'z') 5 ('b', 'x') 7 ('b', 'z') 7 ('c', 'y') 8 I have some working code, but is terribly slow. C = AA.apply(lambda row: ( row[0], row[1], B.ix[row[0]].irow(np.searchsorted(B.ts[row[0]], row[2]))), axis=1).set_index(['a', 'b']) Profiling shows the culprit is obviously B.ix[row[0]].irow(np.searchsorted(B.ts[row[0]], row[2]))). However, standard solutions using merge/join would take too much RAM in the long run. Consider that now I have 1000 a's, assume constant the average number of b's per a (probably 100-200), and consider that the number of observations per a is probably in the order of 300. In production I will have 1000 more a's. 1,000,000 x 200 x 300 = 60,000,000,000 rows may be a bit too much to keep in RAM, especially considering that the data I need is perfectly described by a C like the one I discussed above. How would I improve the performance?

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  • methods of metaclasses on class instances.

    - by Stefano Borini
    I was wondering what happens to methods declared on a metaclass. I expected that if you declare a method on a metaclass, it will end up being a classmethod, however, the behavior is different. Example >>> class A(object): ... @classmethod ... def foo(cls): ... print "foo" ... >>> a=A() >>> a.foo() foo >>> A.foo() foo However, if I try to define a metaclass and give it a method foo, it seems to work the same for the class, not for the instance. >>> class Meta(type): ... def foo(self): ... print "foo" ... >>> class A(object): ... __metaclass__=Meta ... def __init__(self): ... print "hello" ... >>> >>> a=A() hello >>> A.foo() foo >>> a.foo() Traceback (most recent call last): File "<stdin>", line 1, in <module> AttributeError: 'A' object has no attribute 'foo' What's going on here exactly ? edit: bumping the question

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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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  • Parsing html for domain links

    - by Hallik
    I have a script that parses an html page for all the links within it. I am getting all of them fine, but I have a list of domains I want to compare it against. So a sample list contains list=['www.domain.com', 'sub.domain.com'] But I may have a list of links that look like http://domain.com http://sub.domain.com/some/other/page I can strip off the http:// just fine, but in the two example links I just posted, they both should match. The first I would like to match against the www.domain.com, and the second, I would like to match against the subdomain in the list. Right now I am using url2lib for parsing the html. What are my options in completely this task?

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