I am having trouble disassociating many to many relationships...
b = Blog.objects.get(id=1)
e = Entry.objects.get(id=234)
b.entry_set.remove(e)
doesnt seem to work...
how do i disassociate without deleting anything?
Make sure you call b.save() after removing the entry.
Related
At the moment I have a dataset of ingredients. The problem is that it is not very clean because it contains many different names for the same thing. Here are a few examples:
Mehl = Weizenmehl, Mehl Type360
or
Eier = Eier, Ei(er), Ei
I thought of maybe deleting those brackets and making many if statements which are looking for different things like "Mehl" but there I would have to also look for something like "Dinkel" because of
Dinkelmehl != Mehl
I could do it but it would be very laborious because that's a big dataset. Are there some other methods maybe with a dictionary or something? I hope you can help me thank you!
Frederick!
Yes, you can use map method from pandas. First, I would suggest to clean special characters (!"#$%&/) and the use the map for Eier,Ei, Mehl, Tomaten....
I attach the documentation of map: map in df pandas
VG
I'm have a List<Ref<Entity>>. I add new entries to the list like this:
entities.add(Ref.create(new_entry));
modified.add(new_entry);
When I store the entity that contains the list, I store the list itself and all the entities that are in the modified list. This works fine.
The problem is, that I have to work with the entities-list, while I add new entries to it. This requires iterating the list multiple times. The problem here is, that the refs in the list point to old entries (which are already in the datastore) and new entries (which are not yet in the datastore).
This causes the Ref.get()-method to return null for all the yet unstored entries in the list (the ones that are still in the modified-list).
I worked around this by doing this when inserting:
Ref<T> ref = new DeadRef<>(
Key.create(data),
data
);
this.entities.add(ref);
this.modified.add(data);
This way, I can mix stored and unstored entries in one list and Ref.get() always returns a value.
This works, but I have noticed that the refs in the entities-list stay DeadRefs when I store them to the datastore and load them in again.
Will this be a problem? Is there maybe even a better way to accomplish this?
This seems like a bad idea, although I don't know what specific problems you will run into.
The "right answer" is to save your entities first.
Edit: Also look at the documentation for ofy().defer().save(), which can prevent you from issuing a lot of unnecessary save operations.
I have a few variables and here they are, three variables "R1, R2 and R3" each have a size of [40 x 1].
I have a fourth variable U of the same dimension. For every U(i) I need to search for an optimum value within R1(i), R2(i) and R3(i) which would return a single value solution. I intend to plot the optimum value against U9i).I have been trying to wrap my head around the knnsearch function but no luck.
Any one out there who could please help??
Thanks
Well when I can't wrap my head around something, I don't come here first.
A lot of people forget this one because we are online, but read a book on the topic. Have your code open so when you see something in the book, test it out.
Draw out any type of diagram. I call these "Napkin Diagrams", because I write it on anything, even a napkin.
I play with code until my keyboard has no letters left on it, then I keep plugging away until the keys fall off
Explore the language API's
Check for public repositories that you can play with
Google, is okay for a quick reference, but google will not teach you anything other than how to google
I talk my code over with myself all the time, people think I'm nuts, but so do I . . It actually works sometimes.
Then if I still can't get it, I come here with a list of things that I have tried, sample code that has not worked, etc.
I used to hate when people told me this, but that was the best thing anyone could have done for me so I tend to do the same now" Thinking about coding is a big part, but u have to get done wht u can. Then we all know what level u are at. Plus it being the end of semester a lot of these types of questions are homework...
Thinking is good, now turn those thoughts into a conceptual design . It's okay to be wrong in this stage, its all just conceptual
If I understood correctly, this might be what you need:
RR = [R1(:) R2(:) R3(:)];
d = bsxfun(#minus,RR, U(:));
[m mi] = min(abs(d),[],2);
answer = RR(:,mi);
first - put the three vectors into a single matrix:
RR = [R1(:) R2(:) R3(:)];
next, take the difference with U: bsxfun is ideal for this kind of thing
d = bsxfun(#minus,RR, U(:));
Now find the minimum absolute difference for each row:
[m mi] = min(abs(d),[],2);
The corresponding indices should allow you to find the "best fit"
answer = RR(:,mi);
I had to do some mind reading to get to this 'answer', so feel free to correct my misunderstanding of your problem!
update if you just need the highest of the three values, then
val = max([R1(:) R2(:) R3(:)]');
plot(U, val);
should be all you need...
I have a bit of a question regarding why my code seems to hang when I run it. The code is for a project I have in a class, but we spent one class period going over Prolog so much of what I've learned is stuff I've searched around for and have taught myself. I do apologize if my code contains horrendous stylistic errors, but again, as we never formally learned how we 'should' use Prolog, this is based mostly on my own experimentation.
The goal of the segment of code I am writing is, more or less, to form a chain that connects one actor to another through a series of movies that they have been in.
I have a function I am calling that is meant to construct connections between a starting actor, all possible linked actors ending actor, and the list of movies that connects them. This is probably a horribly inefficient method of doing this, however implementing it this way solves two parts of the assignment with one segment of code.
The code that calls the function works, and for the sake of making this simpler to read, I will omit it unless asked to share it. In short, it asserts a globalStartingActor, and passes on two empty lists (ActorList = [] and MovieList = []) to a function doActorAssertions.
In turn, we have doActorAssertions. This is the revised version of it, which should be simplified and easier to read, but lacks the massive commenting that it had previously.
doActorAssertions(ActorsName,ActorList,MovieList) :-
isNotInList(ActorsName,ActorList) ->
(
findMoviesIn(ActorsName,MoviesIn),%finds all movies ActorsName is in
howLong(MoviesIn,LenMoviesIn),%Sees how many movies there are.
(
LenMoviesIn ==0;
(
append(ActorsName,ActorList,UpdatedActorList),%this causes errors!
globalStartingActor(GSAName),%asserted starting actor
assert(connectedActors(GSAName,ActorsName,MovieList)), %says that the GSAName is connected to ActorsName by a list of movies MovieList.
write(actorAsserted),
addAndTraverse(MoviesIn,UpdatedActorList,MovieList) %Goes to propegate all movies the actor is in, then actors in those movies, then recursively calls this function again.
)
)
),
true.
As I said previously, the append tag seemed to be the source of the error! This indeed appears to be the case when I simplify the code to what it is above. I simply comment that append out, and the code body works.
Why, then, is append preventing the code from working properly? I need to have append (or similar function) in that part of the code!
Is ActorsName a list? The variable' name suggests it is, as well as the usage in append/3, but then what isNotInList(ActorsName,ActorList) means? Partial or full disjunction? This could be the cause of the endless loop, maybe you should use the difference of those sets to increment the ActorList.
You should try to avoid assert/1, and instead pass around the state in variables. See this other answer for a schema doing something very similar to what you are attempting here.
This is useless, could be a typo, but then I don't understand the ->
...
),
true.
I think should read
...
); % note the semicolon!
true.
So i have a lot of different model types. Comments, posts, reviews, etc. And I want to join them into one integrated feed. Is there a CakePHP style of merging all this data for display, ordered by timestamp?
There are a lot of messy ways to do this but I wonder if there is some standard way which I am missing. Thanks!
Since the items are from different tables, it's difficult to retrieve them sorted together from the database in any case. Depending on how well organized your data is though, something as non-messy as this should do:
$posts = $this->Post->find(...);
$reviews = $this->Review->find(...);
$comments = $this->Comment->find(...);
$feed = array_merge($posts, $reviews, $comments);
usort($feed, function ($a, $b) {
$a = current($a);
$b = current($b);
return $strtotime($a['created']) - strtotime($b['created']);
});
philosophical? lol
No, I don't think there is one. Although you could write an afterSave() in app_model. Check for the data you're looking for, and if found, put it in Cache. It will probably be messy, but at least it's in one place, and doesn't affect the performance much.
There's definitely no way to merge the data automatically, but instead of firing separate queries for each relationship, you can grab it all at once using CakePHP's Containable behavior.