I have a list of constructed objects called RecentCard which is basically an object with user id, pic, and name. I have created a list arranged in order of most recent interaction based on timestamp. However i need to get rid of the second occurence and onwards of any duplicated object. I am comparing just the ids since users may have the same name or photo, and i cannot remove duplicates from a simple list of uids because then i could lose the order of corresponding photos and names.
For example the list would look something like this :
List<RecentCard> recentCards= [RecentCard(uid:as721dn18j2,name:mike,photourl:https://sadadasd1d1),RecentCard(.....]
I have searched for solutions but all of them are dealing with like primitive types like simple lists of strings and the solutions didn't work for me. For example this post: How to delete duplicates in a dart List? list.distinct()? Read below
The first answer's link is no longer available, the next answer with sets is something i tried but it simply doesnt work i have no idea why maybe because its not a primitive type. The next answer with the queries package didn't work because i was using the list to build a listview.builder and so when i called list.length it said i couldnt call that on an iterable or something. The final solution wouldn't work because it said String is not a subtype of RecentCard.
I tried using two forloops with the second just comparing first value to the next couple but that doesnt work because if a duplicate is found, the object is removed and the length is messed up so some elements get skipped.
Any ideas? I feel like its very simple but im not sure how to do it.
You have to use Set to store seen cards and then filter away those ones that are already in the set.
final seenCards = Set<String>();
final uniqueCards = recentCards.where((card) => seenCards.add(card.uid)).toList();
Related
Trying to figure out the right way to parse key-value pairs produced by a Cypher query:
#app.route('/about')
def about():
data = graph.run("MATCH (n) RETURN n.level")
for record in data:
return render_template("output.html",output=record)
Please disregard the fact that I'm not combining the returned records into a list prior to populating the template. I do get one record as output, and am ok with that for now.
What I'm struggling with is - how do I handle the resulting k/v pair
(u'n.level': u'high')
I mean, if I'm just interested in the value 'high', is there a clean way to get hold of it?
Sorry if this sounds too basic. I do understand, there must be some parsing tools, but at this point, I just don't know where to look.
Sorry, the solution is simple. Flask returns a py2neo.database.record object, which can be indexed just like a list, the only caveat being that the list has only one element (not two, as it might appear).
So, if variable record above equals to (u'n.level': u'high'), record[0] will be equal to 'high'.
And the 'u's can be just ignored altogether, as explained elsewhere on SO.
basically my whole career is based on reading question here but now I'm stuck since I even do not know how to ask this correctly.
I'm designing a SQLITE database which is meant for the construction of data sheets out of existing data sheets. People like reusing stuff and I want to manage this with a DB and an interface. A data sheet has reusable elements like pictures, text, formulas, sections, lists, frontpages and variables. Sections can contain elements -> This can be coped with recursive CTEs - thanks "mu is too short" for that hint. Texts, Formulas, lists etc. can contain variables. At the end I want to be able to manage variables which must be unique per data sheet, manage elements which are an ordered list making up the data sheet. So selecting a data sheet I must know which elements are contained and what variables within the elements are used. I must be able to create a new data sheet by re-using elements and/or creating new ones if desired.
I came so far to have (see also link to screen shot at the bottom)
a list of variables
which (several of them) can be contained in elements
a list of elements
elements make up the
a list of data sheets
Reading examples like
Store array in SQLite that is referenced in another table
How to store a list in a column of a database table
give me already helpful hints like that I need to create for each data sheet a new atomic list containing the elements and the position of them. Same for the variables which are referenced by each element. But the troubles start when I want to have it consistent and actually how to query it.
How do I connect the the variables which are contained within elements and the elements that are contained within the data sheets. How do I check when one element or variable is being modified, which data sheets need to be recompiled since they are using the same variables and/or elements?
The more I think about this, the more it sounds like I need to write my own search tree based on an object oriented inheritance class structure and must not use data bases. Can somebody convince me that a data base is the right tool for my issue?
I learned data bases once but this is quite some time ago and to be honest the university was not giving good lectures since we never created a database by our own but only worked on existing ones.
To be more specific, my knowledge leads to this solution so far without knowing how to correctly query for a list of data sheets when changing the content of one value since the reference is a text containing the name of a table:
screen shot since I'm a greenhorn
Update:
I think I have to search for unique connections, so it would end up in many-to-many tables. Not perfectly happy with it but I think I can go on with it.
still a green horn, how are you guys using correct high lightning for sql?
I am using a static class in my application. It basically uses an access database, and copies itself to various lists.
When the user modifies some data, the data is updates in the list, using LINQ, if there is no entry in the list for the modification then it will add a new item to the list.
This all works fine.
However on the 1st data interrogation, I create the original list, basically all records in the users table, so I have a list lstDATABASERECORDS.
What I do after populating this list I do lstDATABASERECORDSCOMPARISON=lstDATABASERECORDS
this enables me to quickly check whether to use an update or append query.
However when I add to lstDATABASERECORDS a record is added in lstDATABASERECORDSCOMPARISON too.
Can anyone advise?
You are assigning two variables to refer to the same instance of a list. Instead, you may want to try generating a clone of your list to keep for deltas (ICloneable is unfortunately not that useful without additional work to define cloneable semantics for your objects), or use objects that implement IEditableObject and probably INotifyPropertyChanged for change tracking (there's a few options there, including rolling your own).
There's nothing built in to the framework (until EF) that replicates the old ADO recordset capability to auto-magically generate update queries that only attempt to modify changed columns.
This question already has answers here:
Django: __in query lookup doesn't maintain the order in queryset
(6 answers)
Closed 8 years ago.
I've searched online and could only find one blog that seemed like a hackish attempt to keep the order of a query list. I was hoping to query using the ORM with a list of strings, but doing it that way does not keep the order of the list.
From what I understand bulk_query only works if you have the id's of the items you want to query.
Can anybody recommend an ideal way of querying by a list of strings and making sure the objects are kept in their proper order?
So in a perfect world I would be able to query a set of objects by doing something like this...
Entry.objects.filter(id__in=['list', 'of', 'strings'])
However, they do not keep order, so string could be before list etc...
The only work around I see, and I may just be tired or this may be perfectly acceptable I'm not sure is doing this...
for i in listOfStrings:
object = Object.objects.get(title=str(i))
myIterableCorrectOrderedList.append(object)
Thank you,
The problem with your solution is that it does a separate database query for each item.
This answer gives the right solution if you're using ids: use in_bulk to create a map between ids and items, and then reorder them as you wish.
If you're not using ids, you can just create the mapping yourself:
values = ['list', 'of', 'strings']
# one database query
entries = Entry.objects.filter(field__in=values)
# one trip through the list to create the mapping
entry_map = {entry.field: entry for entry in entries}
# one more trip through the list to build the ordered entries
ordered_entries = [entry_map[value] for value in values]
(You could save yourself a line by using index, as in this example, but since index is O(n) the performance will not be good for long lists.)
Remember that ultimately this is all done to a database; these operations get translated down to SQL somewhere.
Your Django query loosely translated into SQL would be something like:
SELECT * FROM entry_table e WHERE e.title IN ("list", "of", "strings");
So, in a way, your question is equivalent to asking how to ORDER BY the order something was specified in a WHERE clause. (Needless to say, I hope, this is a confusing request to write in SQL -- NOT the way it was designed to be used.)
You can do this in a couple of ways, as documented in some other answers on StackOverflow [1] [2]. However, as you can see, both rely on adding (temporary) information to the database in order to sort the selection.
Really, this should suggest the correct answer: the information you are sorting on should be in your database. Or, back in high-level Django-land, it should be in your models. Consider revising your models to save a timestamp or an ordering when the user adds favorites, if that's what you want to preserve.
Otherwise, you're stuck with one of the solutions that either grabs the unordered data from the db then "fixes" it in Python, or constructing your own SQL query and implementing your own ugly hack from one of the solutions I linked (don't do this).
tl;dr The "right" answer is to keep the sort order in the database; the "quick fix" is to massage the unsorted data from the database to your liking in Python.
EDIT: Apparently MySQL has some weird feature that will let you do this, if that happens to be your backend.
Assume that I have a list of employee names from a database (thousands, potentially tens-of-thousands in the near future). To make the problem simpler assume that each firstname/lastname combination is unique (a big if, but a tangent).
I also have a RSS stream of news content that pertains to the business (again, could be in the hundreds of items per day).
What I would like to do is detect if an employees name appears in the several paragraph news item and, if so, 'tag' the item with the person its talking about.
There may be more than one employee named in a single news item so breaking the loop after the first positive match isn't a possibility.
I can certainly brute force things: for every news item, loop over each and every employee name and if a regex expression returns a match, make note of it.
Is there a simpler way in ColdFusion or should I just get on with my nested loops?
Just throwing this out there as something you could do...
It sounds like you'll almost unanimously have significantly more employee names than words per post. Here's how I might handle it:
Have an always-running CF app that will pull in the feeds and onAppStart
Grab all employees from your db
Create an app-scoped look up struct with first names as keys and a struct of last names as values ( you could also add middle names sibling to last names with a 3rd tier if desired ).
So one key in the look up might be "Vanessa" with a struct with 2 keys ( "Johnson" and "Forta" ) as its value.
Then, each article you parse, just listToArray with a space as a delimiter and loop through the array doing a simple structKeyExists with each token. For matches, check the next item in the array as a last name.
I'd guess this would be much more performant processingwise than doing however many searches and also take almost no time to code and you can feed in any future sources extremely simply ( your checker takes one argument, any text on Earth ).
Interested to see what route you go and whether your experiments expose anything new about performance in CF.
Matthew, you have a tall order there, and there are really multiple parts to the challenge/solution. But just in terms of comparing a list of values to a given set of text to see if one of them occur in there, you'll find that there's no one could CF function. BEcause of that, I created a new one, findList, available at cflib:
http://cflib.org/index.cfm?event=page.udfbyid&udfid=1908
It's not perfect, nor as optimal as it could be, but it may be a useful first step or you, or give you some ideas. That said, it suited my need (determine if a given blog comment had reference to any of the blacklisted words). I show it comparing a list of URLs, but it could be any words at all. Hope that's a little helpful.
Another option worth exploring is leveraging the Solr engine that ships with CF now. It will do the string search heavy lifting for you and you can probably focus on dynamically keeping your collections up to date and optimized as new feed items come in.
Good luck!