The database filters the user, then strips off a portion (the list is poor) and then randomly returns a user. SQLAlchemy + Python Collection (set) + random

The things between SQLAlchemy and Flask-sqlalchemy are not too clear.

SQLAlchemy documentation too damn much, day.

The instance that was encountered today.

The user randomly matches, and the system randomly returns a user under certain filter conditions. For the user experience, you have to get rid of the people you already care about.

First get a list of users that meet the filter criteria:

Users = User.query.filter_by (School=form.school.data, Sex=form.sex.data, Status=form.status.data). All ()

And to get a list of people you've followed:

followed = G.user.followed.all ()  

The point is, how do you subtract the other list from the first one? Without this method, the time complexity should be super large with a for loop and if judgment.

Therefore, you should first list to set and then set to find the difference set and then go to the list.

Filter_users = List (set (users)-set (followed))    # Lists to set to find the difference set and then to go to the list

Then we are going to start randomly selecting a user. Find the documentation for the Python random module and find that choice () is a good, random selection in the sequence.

Note that if it is an empty sequence, it will be an error.

Therefore, the following code is:

            If filter_users:                user = Random.choice (filter_users)                Flash (U ' you match to the following users: ')                return redirect (' Profile ', id=user.id)]            else:                Flash (U ' ah oh, no user satisfies this condition ')    # later use the mascot to express, do not use Flash                return render_template ( ' match.html ', form=form)

Above.

Today learned a lot of things, what hash, data structure, time complexity are out.

Cock.

The database filters the user, then removes a portion (the list is poor) and then randomly returns a user. SQLAlchemy + Python Collection (set) + random