I am getting data from my database and one of the fields could contain a large amount of text and I want to limit the amount of text it returns. Basically I am looking for the equivalent to PHP's substr function.
Right now I am grabbing the content from my database by
{{post.First_Name}} {{post.Last_Name}}
Is there a way I can limit the amount of text it returns from this field?
Thanks.
You may wish to use truncatewords filter. You do it like so:
{{ post.First_Name|truncatewords:3 }}
You can gain even more precision if you want to. You can learn more about filters, and this one is particular here. You can gain even more fine-grain control with truncatechars if you so wish.
Related
I was wondering if anyone has every had experience with breaking a string up in quicksight and using certain aspects of the string. My example is a data set that returns tags like this "animals|funny|dog-park" I have used "split(tags,'|',1)" but then all that gets returned is the first part(animals). I have also tried a combination of ifelse->locate->split with no luck. Is there a way to split these tags to where they are all usable (animals) & (funny) or (funny) & (dog-park), etc.? Say the article associated will then be broken up into one tag but also another separately? I know this will end up being a calculated field most likely. Thank you in advance!
Since QuickSight does not support any form of nested fields (including objects and list) in analysis, you need to normalise this into separate rows before feeding the data to QuickSight.
Otherwise, if you leave it as is, you would be limited to filtering using string contains and doing string lookup in calculated fields - nevertheless you would not be able to use these tags as categories (such as in colours field well of visuals).
Is there any way to group a table by a text field, having in count that this text field is not always exactly the same?
Example:
select city_hotel, count(city_hotel)
from hotels, temp_grid
where st_intersects(hotels.geom, temp_grid.geom)
and potential=1
and part=4
group by city_hotel
order by (city_hotel) desc
The output I get is the expected, for example, City name and count:
"Vassiliki ";1
"Vassiliki";1
"Vassilias, Skiathos";1
"Vassilias";5
"Vasilikí";25
"Vasiliki";23
"Vasilias";1
But I'd want to group more this field, and get only one "Vasiliki" (or an array with all, this is not a problem) and a count of all the cells containing something similar between them.
I do not know if could this be possible. Maybe some function to text analysis or something similar?
SELECT COUNT(*), `etc` FROM table GROUP BY textfield LIKE '%sili%';
// The '%' is a SQL wildcard, which matches as many of any character as required.
You could do something like the above, choosing a word for the 'like' that best fits the spellings that your users have used.
Something that can help with that would be to do a
SELECT COUNT(*), textfield FROM table GROUP BY textfield ORDER BY textfield;
And selecting the most 'average' spelling for your words.
Otherwise you're starting to get into a bit of language processing, and for that you will want to write some code outside of SQL.
This would be something like https://en.wikipedia.org/wiki/Damerau%E2%80%93Levenshtein_distance
To find word's that are the same within an arbitrary margin of error.
There is a MySQL implementation here that you should be able to transpose as needed
https://stackoverflow.com/a/6392380/1287480
(credit https://stackoverflow.com/a/3515291/1287480)
.
(Personal thoughts on the topic)
You Really Really want to think about limiting the input from users that can give you this issue in the first place. It's far far better to give the users a list of places to select from, than it is to push potentially 'dirty' information into your database. That eventually always winds up with you trying to clean the information at a later time. A problem that has kept many people employed for many years.
We have a ColdFusion based site that involves a large number of 'document authors' that have little or no knowledge of HTML. The 'documents' they create are comprised of HTML stored in a table in the database. They use a CKEDITOR interface. The content that they create is output into specific area of the page. The document frequently has tons of technical terms that readers may not be familiar with that we would like to have tooltips automatically show up for.
I and the other programmer want to have some code insert 'tooltip' code into the page based on a list of words in a table on our SQL server. The 'dictionary' table in our database has a unique ID, the word/phrase we will look for and a corresponding definition that would be displayed in the tooltip.
For instance, one of the word/phrases we will be looking for is 'Scrum Master'. If it occurs in the document area, we need to insert code around the words to create a tooltip. To do that, we need to see if certain conditions exist. Are the words within an anchor tag? If yes, is there already a title value for the tag (title is used to contain the info to be displayed in a tooltip)? If a title tag exists, don't do anything. If the words are not in an anchor tag, then we would put anchor tags around the words along with the title that will contain the definition.
The tooltip code we use is via jQuery (http://jqueryui.com/tooltip/). It is quick and simple to use. We just need to figure out how to use it dynamically based on our dictionary table.
Do you have any suggestions of how to go about this?
I was hoping that jSoup might have a function that I could use, but that doesn't seem to be the right technology for what I want to do, but I could be wrong and I am happy to be corrected!
We have a large number of these documents and so manually inserting and maintaining the tooltip code is just not an option.
Update you content with something like:
strOut = ReplaceList(strIn, ValueList(qryTT.find), ValueList(qryTT.replace));
Since words are delimited by spaces, the qryTT.find needs to have spaces. The replace column is going to need to include some of the original content. You are going to have to be careful with words followed by a comma or a period too.
I would cache the results because I would expect it to be memory intensive.
In my html file, how can I output the size of the queryset that I am using (for my debugging purposes)
I've tried
{{ len(some_queryset) }}
but that didn't work. What is the format?
Give {{ some_queryset.count }} a try.
This is better than using len (which could be invoked with {{ some_queryset.__len__ }}) because it optimizes the SQL generated in the background to only retrieve the number of records instead of the records themselves.
some_queryset.count() or {{some_queryset.count}} in your template.
dont use len, it is much less efficient. The database should be doing that work. See the documentation about count().
However, taking buffer's advice into account, if you are planning to iterate over the records anyway, you might as well use len which will involve resolving the queryset and making the resulting rows resident in main memory - this wont go to waste because you will visit these rows anyway. It might actually be faster, depending on db connection latency, but you should always measure.
Just to highlight #Yuji'Tomita'Tomita comment above as a separate answer:
There is a filter called length to call len() on anything.
So you could use:
{{ some_queryset|length }}
The accepted answer is not entirely correct. Whether you should use len() (or the length-filter in a template) vs count() depends on your use case.
If the QuerySet only exists to count the amount of rows, use count().
If the QuerySet is used elsewhere, i.e. in a loop, use len() or |length. Using count() here would issue another SELECT-query to count the rows, while len() simply counts the amount of cached results in the QuerySet.
From the docs:
Note that if you want the number of items in a QuerySet and are also retrieving model instances from it (for example, by iterating over it), it’s probably more efficient to use len(queryset) which won’t cause an extra database query like count() would.
Although it seems that with related objects that you have already eager-loaded using prefetch_related(), you can safely use count() and Django will be smart enough to use the cached data instead of doing another SELECT-query.
So, my problem is this. I have a legacy MySQL database that I'm building a shiny new Django application over. For whatever reason, some fairly daft design decisions were made—such as all fields, no matter what they contain, being stored as varchars—but because since other systems that I'm not rewriting depend on that same data I can't destructively change that schema at all.
I want to treat a certain field—the stock quantity on hand—as an integer, so that in my template I can check its amount and display a relevant value (basically, if there are more than 100 items available, I want to just display "100+ Available").
The existing value for stock quantity is stored as, oddly, a varchar holding a float (as if it's possible to have fractional amounts of an item in stock):
item.qty: u"72.0"
Now, I figure as a worst case I can use QuerySet.values(), and iterate over the results, replacing each stock quantity with an int() parsed version of itself. Something like ...
item_list = items.values()
for item in item_list:
item['qty'] = int(float(item['qty']))
... but won't that cause my QuerySet to evaluate itself completely? I confess to being fairly ignorant of the process by which Django handles lazy execution of queries, but it seems like working with actual values would mean evaluating the query before it needs to.
So, am I complaining about nothing (I mean, it's definitely evaluating these values in the template anyway), or is there a better way to do what I need to do?
Yes, iterating through in the view would evaluate the entire queryset. That may or not be what you want - for example, if you're paginating, the paginator limits the query automatically, so you don't want to evaluate the whole thing separately.
I would approach this in a different way, by calling a function in the template to format the data. You can either do this with a method on the model, if there's just one field you want to format:
class Item(models.Model):
...
def get_formatted_qty(self):
return int(float(self.qty))
and call it:
{{ item.get_formatted_qty }}
Or, to make it more general, you can define a custom filter in your templatetags:
#register.filter
def format_value(value):
return int(float(value))
{{ item.qty|format }}