I have a data structure that declares relationships like this (pseudocode):
class User:
...
class Rating:
rater = User
post = Post
class Post:
ratings = hasmany(Rating)
page_id = ...
I'm building a website using these models, and I'd I'm lazy, so I pass my template the current logged in User, and a bunch of Posts on the current page. My page needs to know what rating the logged in user gave to each Post, so I use SQLAlchemy's one-instance-per-session feature:
posts = session.query(Post).filter(Post.page_id==current_pageid)
ratings = session.query(Post, Rating)\
.filter(Rating.rater==user.id)\
.filter(Post.page_id==current_pageid)
for post in posts:
post.user_rating = None # default value
for post, rating in ratings:
post.user_rating = rating
Then I pass my template the posts list. Is this ugly awful practice? Can I do it some better way?
What you are doing is good enough, except that your query is lacking a WHERE clause between the Post and Rating:
# ...
.filter(Post.id==Rating.post_id)\
But you can also get the result in one query:
qry = (session.query(Post, Rating).
outerjoin(Rating, and_(Post.id==Rating.post_id, Rating.user_id==user.id)).
filter(Post.page_id==current_pageid)
)
res = qry.all() # you can return *res* already to a view, but to get to your results, do below as well:
for post, rating in res:
post.user_rating = rating
posts = [post for post, rating in res]
return posts
Note that in your case posts is not really a list, but a query, and if you iterate over it second time, you might lose the user_rating attribute. You should be cautious returning session-bound objects like query to a view. It is safer to return lists like in the same code above. To fix your code, just add .all() to the query:
posts = session.query(Post).filter(Post.page_id==current_pageid).all()
Yes, it's bad practice. And it even might (in theory) beat you at some moment, e.g. when you query from the same session without clearing it for some post SQLAlchemy will return you the same cached object with already filled rating for some user unrelated to the current context. In practice it will work find in most cases.
Why not just pass a list of (post, rating) pairs to template? Most modern template engines available for Python can iterate over the list of pairs.
BTW, you can fetch both posts and ratings with single query (rating object will be None for OUTER JOIN when it's missing):
session.query(Post, Rating).select_from(Post)\
.outerjoin(Rating, (Post.id==Rating.post_id) & (Rating.rater==…))\
.filter(Post.page_id==…)
Related
I have been trying to design a page in Django that works as follows.
My "list_books.html" page lists every book object handed to it.
I have a number of functions in views.py that determine what values would be used to determine the books shown on that page (i.e. all books by an author, all books in a series, all books with the same publication year)
ex.
#with_person_email
def book_list_author(request, person):
return show_book_list(request, person.books, { 'author': person })
def show_book_list(request, blist, template_args, **kwargs):
# this is just the defaults, will be replaced by data.update below
data = { 'genre': None }
try:
# filters the list based on the keyword arguments
blist = dataview.book_list(blist, **kwargs)
except dataview.DataViewError as e:
blist = None
data['error'] = str(e)
try:
data['books'] = RequestPages(request, blist, desc=True)
except Exception as e:
if not utils.is_db_regex_exception(e):
raise
data['books'] = None
data['error'] = 'Invalid regex.'
data['genres'] = models.Genre.objects.order_by('kind', 'name')
data.update(kwargs)
data.update(template_args)
return render(request, 'book_list.html', data)
book_list.html has a for loop that goes through each book and prints information about it. However, I have a boolean on the book model called "is_archived".
I want to be able to both set "is_archived" on the book from book_list.html, and filter the books shown between archived and not. I can do both of these things currently using a form that calls the following function handing it only archived books. However, this form has no idea what the previous criteria was to sort the books, so it shows all the archived books.
def commit_list_archived(request):
return show_commit_list(request, models.Books.objects.filter(is_archived=True), { 'archived': True })
Settings the boolean is accomplished with a simple button that calls a view which changes the boolean field, and then returns to the previous page.
I want to be able to toggle between archived and non archived books. I tried using <input type="hidden" name="next" value="{{ request.path }}"> on the form to the archived posts to determine the previous criteria (author, year, genre, etc), however this doesn't seem to work.
I also considered using a checkbox that would toggle the books being shown, but I couldnt determine how to access the information of the checkbox form views.
For cleanliness sake I would like to remain on the books_list.html page, and just hand it either archived or none archived books. Again the problem is finding some way to call the right function both before and after view the archived books, to ensure I am still sorting by the same criteria.
Any help would be much appreciated.
Disregard I figured it out. I just sent a query parameter ?archived=true and have the views check for this parameter and filter the commits they send to the html template accordingly
I am trying to figure out the best method of accessing all the matching microseries found in the Assessment class (table) in my database. I am trying to create a link that will send a user to those matching microseries. I am new and want to better understand the nuts and bolts of front-end engineering. I also have not seen a similar question asked here on Stacks.
I am not using JSON or XML yet, so this is a static HTML process. I have a few routes that access assessments at the moment, e.g.:
config.add_route('assessments', '/assessments')
config.add_route('assessment', '/assessments/{id:\d+}')
What I would like to better understand while implementing a method of finding matching microseries in the Assessment table and sending the user to a new page with those matching series:
How routes work, especially when accessing an attribute of a class, e.g. Assessment.microseries.
The goal of View code to convey the method mentioned above.
Pyramid links and Pyramid on Routes and URL Dispatch
Using: Python 2.7, SQLAlchemy, Pyramid
Assessment table:
class Assessment(Base):
__tablename__ = 'assessments'
id = Column(Integer, primary_key=True)
name = Column(String(50), unique=True)
text = Column(String(2000))
microseries = Column(Integer)
# more code
def __init__(self, name, text, user, video, categories, microseries):
# more code
API for interacting with an assessment is based on CRUD- create, retrieve, update and delete.
View Code:
this is not doing what I need it to do as I don't have a form of link to send the user to the matching series, e.g. Link1 would send a user to a new view with GET for all subseries of Link1: 1a, 1b, 1c....
#view_config(route_name='assessments', request_method='GET', renderer='templates/unique_assessments.jinja2', permission='create')
def view_unique_microseries_group(request):
logged_in_userid = authenticated_userid(request)
if logged_in_userid is None:
raise HTTPForbidden()
all_assessments = api.retrieve_assessments() #all assessments in a list
assessments_by_microseries = {} #dictonary
for x in all_assessments:
if x.microseries in assessments_by_microseries:
print("Already seen this microseries: %s" % x.microseries)
else:
assessments_by_microseries[x.microseries] = x
unique_assessments = sorted(assessments_by_microseries.values()) #.values() method to get the, err, values of the dict.
print 'unique_assessments:', unique_assessments
#a = HTTPSeeOther(location=request.route_url('view_microseries'))
return {'logged_in': logged_in_userid, 'unique_assessments': unique_assessments} #need to send some kind of list that can be shown on the template to send a user to the appropriately matching set of microseries
Imagine that:
I have "Posts", "Users", "UserFollowUser" models in a Django app...
I want to get all the POSTS from my POST model but only for people that I FOLLOW.
Every POST has a USER id of the user who is the author.
I mean, there's a register that says:
"Cris" follows "Larry"
I want to get the posts from Larry and some other people I follow.
I tried:
follows = UserFollowUser.objects.get(follower = request.user) #I AM request.user
posts = Post.objects.filter(user = follows.followed).order_by('-id')
But I can only get posts from ONE person because of the "GET" function in objects object.
What you need to do is get an array of user ids for your followers. Then use the __in syntax to make a query where you are asking for all posts whose user id is in the set of user ids of your followers. The code would look something like this:
follower_user_ids = UserFollowUser.objects.filter(follower__user_id = request.user.id)\
.values_list('follower__user_id', flat=True)\
.distinct()
posts = Post.objects.filter(user_id__in=follower_user_ids)
*this assumes UserFollowUser.follower is a foreign key to the User table.
This is code if you want to show posts of all users logged in user follows also your own posted posts in the feed:
follows_users = user.profile.follows.all()
follows_posts = Post.objects.filter(author_id__in=follows_users)
user_posts = Post.objects.filter(author=user)
post_list = (follows_posts|user_posts).distinct().order_by('-date_posted')
You can always take reference for social media django clone from https://github.com/uttampatel007/nccbuddy
I have written code for managing conditional insert/update/delete to
multiple tables from single form in 'web2py'.
I agree, the code is in very raw form & may not be ‘pythonic’.
There are code repeatitions.
But at least I have something to go ahead & build a refined
structure.
MODELS:
db.define_table('mdlmst',
Field('mdlmstid','id'),
Field('mdlmstcd'),
Field('mdlmstnm'),
migrate=False,
format='%(mdlmstnm)s'
)
db.define_table('wrmst',
Field('wrmstid','id'),
Field('wrmstcd'),
Field('wrmstnm'),
migrate=False,
format='%(wrmstnm)s'
)
db.define_table('extwrmst',
Field('extwrmstid','id'),
Field('extwrmstcd'),
Field('extwrmstnm'),
migrate=False,
format='%(extwrmstnm)s'
)
from the FORM, data will be populated in the following two tables
db.define_table('mdlwr',
Field('mdlwrid','id'),
Field('mdlmstid',db.mdlmst),
Field('wrmstid',db.wrmst),
migrate=False
)
db.define_table('mdlextwr',
Field('mdlextwrid','id'),
Field('mdlmstid',db.mdlmst),
Field('extwrmstid',db.extwrmst),
migrate=False
)
CONTROLLERS:
‘modelwar’ controller will render the records from ‘mdlmst’ table
def modelwar():
models = db(db.mdlmst.mdlmstid>0).select(orderby=db.mdlmst.mdlmstnm)
return dict(models=models)
after clicking a particular record, ‘war_edit’ controller will
manage the tables – ‘mdlwr’ & ‘mdlextwr’
def war_edit():
mdl_id = request.args(0)
mdl_id is a variable identifying the ‘mdlmstid’ (which record to be modified)
mdl_nm = request.args(1)
mdl_nm is a variable for getting the ‘mdlmstnm’
warset = db(db.mdlwr.mdlmstid==mdl_id) # fetch a set
extwarset = db(db.mdlextwr.mdlmstid==mdl_id) # fetch a set
warlist = db(db.mdlwr.mdlmstid==mdl_id).select() # get a ROW object
extwarlist = db(db.mdlextwr.mdlmstid==mdl_id).select() # get a ROW object
form_war=FORM(TABLE(TR("Basic Warranty",
SELECT(_type="select",_name="baswar",*[OPTION(x.wrmstnm,_value=x.wrmstid)
for x in db().select(db.wrmst.ALL)]),
TR("Extended Warranty",
SELECT(_type="select",_name="extwar",*[OPTION(x.extwrmstnm,_value=x.extwrmstid)
for x in db().select(db.extwrmst.ALL)]),
TR("", INPUT(_type='submit',_value='Save')), ))))
pre-populate the fields in‘form_war’
if len(warlist)>0:
form_war.vars.baswar = warlist[0].wrmstid
if len(extwarlist)>0:
form_war.vars.extwar = extwarlist[0].extwrmstid
after successful form submission, manage the table 'mdlwr'
if form_war.accepts(request.vars, session):
if there was any record in the list fetched from database & sent to FORM,
if len(warlist)>0:
delete if value returned from FORM field is blank, else update
if form_war.vars.baswar==''
warset.delete()
else:
warset.update(wrmstid=form_war.vars.baswar)
else insert
else:
db.mdlwr.insert(mdlmstid=mdl_id, wrmstid=form_war.vars.baswar)
Similarly, manage the table 'mdlextwr'
if len(extwarlist)>0:
if form_war.vars.extwar=='':
extwarset.delete()
else:
extwarset.update(extwrmstid=form_war.vars.extwar)
else:
db.mdlextwr.insert(mdlmstid=mdl_id, extwrmstid=form_war.vars.extwar)
response.flash = 'Warranty definition saved'
return dict(form_war=form_war,mdlnm=mdl_nm)
VIEW for 'mdlmst' table
{{response.files.append(URL(r=request,c='static',f='jquery.dataTables.min.j
s'))}}
{{response.files.append(URL(r=request,c='static',f='demo_table.css'))}}
{{extend 'layout.html'}}
jQuery(document).ready(function()
{ jQuery('.smarttable').dataTable();});
Modelwise Warranty Master
Model IDModel CodeModel Name
{{for model in models:}}
{{=model.mdlmstid}}
{{=model.mdlmstcd}}
{{=model.mdlmstnm}}
{{=A('edit
warranty',_href=URL('war_edit',args=[model.mdlmstid,model.mdlmstnm]))}}
{{pass}}
Pl. tell me if I have coded anything stupid here.
I would highly welcome any ideas/suggestions for improvements.
Thanks,
Vineet
Your database design looks strange to me.
In each table you have a field of type 'id'. This will replace the id field automatically generated by web2py - a bad idea. From the web2py book: "Do not declare a field called "id", because one is created by web2py anyway. Every table has a field called "id" by default. It is an auto-increment integer field (starting at 1) used for cross-reference and for making every record unique, so "id" is a primary key"
You have created a many to many relationship between table 'mdlmst' and 'wrmst' and another many to many relationship between 'mdlmst' and 'extwrmst'. While this is not necessarily wrong, it strikes me as extremely unlikely this is what you want.
My feeling is that your database design needs work. This should be sorted out before you start designing forms.
I am trying to understand the 1-to-many relationships in datastore; but I fail to understand how query and update the record of a user when the model includes ReferenceProperty. Say I have this model:
class User(db.Model):
userEmail = db.StringProperty()
userScore = db.IntegerProperty(default=0)
class Comment(db.Model):
user = db.ReferenceProperty(User, collection_name="comments")
comment = db.StringProperty()
class Venue(db.Model):
user = db.ReferenceProperty(User, collection_name="venues")
venue = db.StringProperty()
If I understand correctly, the same user, uniquely identified by userEmail can have many comments and may be associated with many venues (restaurants etc.)
Now, let's say the user az#example.com is already in the database and he submits a new entry.
Based on this answer I do something like:
q = User.all()
q.filter("userEmail =", az#example.com)
results = q.fetch(1)
newEntry = results[0]
But I am not clear what this does! What I want to do is to update comment and venue fields which are under class Comment and class Venue.
Can you help me understand how this works? Thanks.
The snippet you posted is doing this (see comments):
q = User.all() # prepare User table for querying
q.filter("userEmail =", "az#example.com") # apply filter, email lookup
- this is a simple where clause
results = q.fetch(1) # execute the query, apply limit 1
the_user = results[0] # the results is a list of objects, grab the first one
After this code the_user will be an object that corresponds to the user record with email "az#example.com". Seing you've set up your reference properties, you can access its comments and venues with the_user.comments and the_user.venues. Some venue of these can be modified, say like this:
some_venue = the_user.venues[0] # the first from the list
some_venue.venue = 'At DC. square'
db.put(some_venue) # the entry will be updated
I suggest that you make a general sweep of the gae documentation that has very good examples, you will find it very helpful:
http://code.google.com/appengine/docs/python/overview.html
** UPDATE **: For adding new venue to user, simply create new venue and assign the queried user object as the venue's user attribute:
new_venue = Venue(venue='Jeferson memorial', user=the_user) # careful with the quoting
db.put(new_venue)
To get all Comments for a given user, filter the user property using the key of the user:
comments = Comment.all().filter("user =", user.key()).fetch(50)
So you could first lookup the user by the email, and then search comments or venues using its key.