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  • pandas read rotated csv files

    - by EricCoding
    Is there any function in pandas that can directly read a rotated csv file? To be specific, the header information in the first col instead of the first row. For example: A 1 2 B 3 5 C 6 7 and I would like the final DataFrame this way A B C 1 3 5 2 5 7 Of corse we can get around this problem using some data wangling techniques like transpose and slicing. I am wondering there should be a quick way in API but I could not find it.

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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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  • Getting child elements that are related to a parent in same table

    - by Madawar
    I have the following database schema class posts(Base): __tablename__ = 'xposts' id = Column(Integer, primary_key=True) class Comments(Base): __tablename__ = 'comments' id = Column(Integer, primary_key=True) comment_parent_id=Column(Integer,unique=True) #comment_id fetches comment of a comment ie the comment_parent_id comment_id=Column(Integer,default=None) comment_text=Column(String(200)) Values in database are 1 12 NULL Hello First comment 2 NULL 12 First Sub comment I want to fetch all Comments and sub comments of a post using sqlalchemy and have this so far qry=session.query(Comments).filter(Comments.comment_parent_id!=None) print qry.count() Is there a way i can fetch the all the subcomments of a comment in a query i have tried outerjoin on the same table(comments) and it seemed stupid and it failed.

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  • How do I relate two models/tables in Django based on non primary non unique keys?

    - by wizard
    I've got two tables that I need to relate on a single field po_num. The data is imported from another source so while I have a little bit of control over what the tables look like but I can't change them too much. What I want to do is relate these two models so I can look up one from the other based on the po_num fields. What I really need to do is join the two tables so I can do a where on a count of the related table. I would like to do filter for all Order objects that have 0 related EDI856 objects. I tried adding a foreign key to the Order model and specified the db_column and to_fields as po_num but django didn't like that the fact that Edi856.po_num wasn't unique. Here are the important fields of my current models that let me display but not filter for the data that I want. class Edi856(models.Model): po_num = models.CharField(max_length=90, db_index=True ) class Order(models.Model): po_num = models.CharField(max_length=90, db_index=True) def in_edi(self): '''Has the edi been processed?''' return Edi856.objects.filter(po_num = self.po_num).count() Thanks for taking the time to read about my problem. I'm not sure what to do from here.

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  • Sqlalchemy complex in_ clause

    - by lostlogic
    I'm trying to find a way to cause sqlalchemy to generate sql of the following form: select * from t where (a,b) in ((a1,b1),(a2,b2)); Is this possible? If not, any suggestions on a way to emulate it? Thanks kindly!

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  • What's the straightforward way to implement one to many editing in list_editable in django admin?

    - by Nate Pinchot
    Given the following models: class Store(models.Model): name = models.CharField(max_length=150) class ItemGroup(models.Model): group = models.CharField(max_length=100) code = models.CharField(max_length=20) class ItemType(models.Model): store = models.ForeignKey(Store, on_delete=models.CASCADE, related_name="item_types") item_group = models.ForeignKey(ItemGroup) type = models.CharField(max_length=100) Inline's handle adding multiple item_types to a Store nicely when viewing a single Store. The content admin team would like to be able to edit stores and their types in bulk. Is there a simple way to implement Store.item_types in list_editable which also allows adding new records, similar to horizontal_filter? If not, is there a straightforward guide that shows how to implement a custom list_editable template? I've been Googling but haven't been able to come up with anything. Also, if there is a simpler or better way to set up these models that would make this easier to implement, feel free to comment.

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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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  • Setting up repoze.who with make_redirecting_plugin

    - by Timmy
    my file is: [plugin:form] use = repoze.who.plugins.form:make_redirecting_plugin login_form_url = /account/signin login_handler_path = /account/login logout_handler_path = /account/logout [identifiers] plugins = form;browser auth_tkt i created a form on /account/signin, but it doesnt find the identity? what has to be on the form?

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  • How to use R-Tree for plotting large number of map markers on google maps

    - by Eeyore
    After searching SO and multiple articles I haven't found a solution to my problem. What I am trying to achieve is to load 20,000 markers on Google Maps. R-Tree seems like a good approach but it's only helpful when searching for points within the visible part of the map. When the map is zoomed out it will return all of the points and...crash the browser. There is also the problem with dragging the map and at the end of dragging re-running the query. I would like to know how I can use R-Tree and be able to achieve the all of the above.

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  • Creating form object for variable kind of form.

    - by Bunny Rabbit
    i want to create a form for users to submit questions in django ..so far the models i have created are class Question(models.Model): statement=models.CharField(max_length=100) class Choice(models.Model): statement=models.CharField(max_length=100) value=models.IntegerField() question=models.ForeignKey(Question) Now i want to write a Form class for creating a above form but the problem is the number of choices are variable,a user can decide how many choices a question must have .How do i do that in django?

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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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  • 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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  • 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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  • SQLAlchemy: a better way for update with declarative?

    - by hadrien
    I am a SQLAlchemy noob. Let's say I have an user table in declarative mode: class User(Base): __tablename__ = 'user' id = Column(u'id', Integer(), primary_key=True) name = Column(u'name', String(50)) When I know user's id without object loaded into session, I update such user like this: ex = update(User.__table__).where(User.id==123).values(name=u"Bob Marley") Session.execute(ex) I dislike using User.__table__, should I stop worrying with that? Is there a better way to do this? Thanx!

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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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  • 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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  • 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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  • 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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  • Estimating the boundary of arbitrarily distributed data

    - by Dave
    I have two dimensional discrete spatial data. I would like to make an approximation of the spatial boundaries of this data so that I can produce a plot with another dataset on top of it. Ideally, this would be an ordered set of (x,y) points that matplotlib can plot with the plt.Polygon() patch. My initial attempt is very inelegant: I place a fine grid over the data, and where data is found in a cell, a square matplotlib patch is created of that cell. The resolution of the boundary thus depends on the sampling frequency of the grid. Here is an example, where the grey region are the cells containing data, black where no data exists. OK, problem solved - why am I still here? Well.... I'd like a more "elegant" solution, or at least one that is faster (ie. I don't want to get on with "real" work, I'd like to have some fun with this!). The best way I can think of is a ray-tracing approach - eg: from xmin to xmax, at y=ymin, check if data boundary crossed in intervals dx y=ymin+dy, do 1 do 1-2, but now sample in y An alternative is defining a centre, and sampling in r-theta space - ie radial spokes in dtheta increments. Both would produce a set of (x,y) points, but then how do I order/link neighbouring points them to create the boundary? A nearest neighbour approach is not appropriate as, for example (to borrow from Geography), an isthmus (think of Panama connecting N&S America) could then close off and isolate regions. This also might not deal very well with the holes seen in the data, which I would like to represent as a different plt.Polygon. The solution perhaps comes from solving an area maximisation problem. For a set of points defining the data limits, what is the maximum contiguous area contained within those points To form the enclosed area, what are the neighbouring points for the nth point? How will the holes be treated in this scheme - is this erring into topology now? Apologies, much of this is me thinking out loud. I'd be grateful for some hints, suggestions or solutions. I suspect this is an oft-studied problem with many solution techniques, but I'm looking for something simple to code and quick to run... I guess everyone is, really! Cheers, David

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