How check if input element is already in query in Flask? - flask

Question

user input some tags, I have to chack if it is alredy in query and if not I save it. I have 2 different base, one for post, another for tag, and then I create post I use Tag bases objects. and if my post tag isnot in Tag's base I create new record for it.
if tag_name not in tags:
new_tag = Tag(tag_name, user)
db.session.add(new_tag)
db.session.commit()
this is how check and create new record but actually it doesnt work properly.
this is whole function:
def get_user(user_id):
user = User.query.filter_by(id = user_id).first()
tags = Tag.query.order_by(Tag.date_created).all()
# posts = Post.query.order_by(Post.date_created).all()
form = questionForm()
total_likes = 0
if user.posts:
for likes in user.posts:
total_likes+=1
if form.validate_on_submit():
user = current_user.id
tag_name = request.form.get('tag_name')
if tag_name not in tags:
new_tag = Tag(tag_name, user)
db.session.add(new_tag)
db.session.commit()
post = Post(form.heading.data, form.text.data, user, tag_name)
db.session.add(post)
db.session.commit()
flash('posted succesfuly')
return render_template("profile.html", user = user, form=form, total_likes = total_likes,tags = tags)
return render_template("profile.html", user = user, form=form, total_likes = total_likes, tags = tags)
whats my Tag class:
class Tag(db.Model):
__tablename__='tag'
id =db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(15), nullable = False, unique=True, index=True)
date_created = db.Column(db.DateTime, default = datetime.utcnow())
author = db.Column(db.Integer, db.ForeignKey('user.id', ondelete="CASCADE"), nullable=False)
def __init__(self, name, author, date_created = datetime.utcnow()):
self.name=name
self.author = author
my form class :
class questionUpdateForm(FlaskForm):
heading = StringField('heading', [Length(min=2, max=50),
DataRequired(message='Question ')])
# tag = StringField('Programming Language')
text = StringField('Question', [Length(min=2, max=1000),
DataRequired(message='description')])
and jinja template :
<div >
<label for="states">Choose or Create Tag</label>
<input class="form-control" type="text"name='tag_name' id="tag_name" name="states" list="states-list" value={{update_post.tags}}>
<datalist id="states-list">
{%for tag in tags%}
<option>{{tag.name}}</option>
{%endfor%}
</datalist>
</div>

Answer 1

What you need to do is something like this:
if tag_name not in {tag.name for tag in tags}:
new_tag = Tag(tag_name, user)
db.session.add(new_tag)
db.session.commit()
because right now you are just searching if the given name is in the tag objects, which doesn't really make sense.
This will search if the tag_name is in the set of all distinct existing tag names.