如何将SQLite中的一个值（根据其他两个值）分配给我的Python变量？

Question

I'm trying to create a simple online login form using Python and SQLite3:

user_email = request.forms.get("email")
user_password = request.forms.get("password")
connection = sqlite3.connect("/home/hassanrashid/mysite/users.db")
c = connection.cursor()
c.execute("SELECT UserName from account WHERE UserEmail=? AND UserPassword=?", (user_email, user_password))

The email and password values entered into the html form are assigned to the user_email and user_password variables respectively. What I'm trying to do is, once the user logs in, he is greeted with a welcome message ("Welcome, UserName!").

My question is, how do I assign the UserName value from my SQLite database table to my Python variable user_name ?

I've also tried this code:

user_name = c.execute("SELECT UserName from account WHERE UserEmail=?", (user_email)).fetchone()

But that gives me an error: "Incorrect number of bindings supplied. The current statement uses 1, and there are 15 supplied." There are 15 rows in my database. I'm assuming that the criteria ( WHERE UserEmail=? ) isn't being applied.

How do I fix this?

Answer 1

user_name = c.execute("SELECT UserName from account WHERE UserEmail=?", (user_email)).fetchone()

Two issues with this:

1. (user_email) is not a tuple, so you are not passing a 1-element tuple to execute() . Instead, pass (user_email,) to make a 1-element tuple.

2. The return value of fetchone() will return the whole result row as a tuple. If there is only one column in the row, you will still get a 1-element tuple back. You need to unpack the tuple first in order to fix this:

query = "SELECT UserName from account WHERE UserEmail=?"
result = c.execute(query, (user_email,)) 

# either store the row tuple first
row = result.fetchone()
user_name = row[0]

# or you could unpack the tuple immediately (note the trailing comma)
user_name, = result.fetchone()