python database application try except block

Question

this is a login function in an application interacting with a database in postresql. I'm new to python and currently both print statements in the except blocks are being executed. The error is in: cur.execute(mtype, (member_id, )) Any ideas about why much appreciated.

def check_login(member_id, password):

    conn = database_connect()
    if(conn is None):
        return None
    cur = conn.cursor()
    try:
        mtype = """SELECT 'athlete' FROM athlete
                        WHERE member_id=%s
                        UNION
                        SELECT 'official' FROM official
                        WHERE member_id=%s
                        UNION
                        SELECT 'staff' FROM staff
                        WHERE member_id=%s"""
        cur.execute(mtype, (member_id, ))
        user_type = cur.fetchone()
    except:
        print("Error retrieving member type")


    try:
        sql = """SELECT member_id, title, given_names AS first_name, family_name, country_name, place_name AS residence
                 FROM public.country JOIN public.member USING (country_code) JOIN public.place ON (accommodation = place_id)
                 WHERE member_id=%s AND pass_word=%s"""

        cur.execute(sql, (member_id, password))
        user_data = cur.fetchone()

        tuples = {
            'member_id': user_data[0],
            'title': user_data[1],
            'first_name': user_data[2],
            'family_name': user_data[3],
            'country_name': user_data[4],
            'residence': user_data[5],
            'member_type': user_type[0]
        }
        cur.close()
        conn.close()
        return tuples
    except:
        print("Error Invalid Login")
        cur.close()
        conn.close()
        return None

You are catching all exceptions and asking why an exception is thrown without showing us the exception. — DeepSpace
– DeepSpace, Commented Jun 3, 2017 at 10:25
DO you want to know why the exceptions are hit in the first place? Or do you want to know why the exceptions are hit at all? — Luke101
– Luke101, Commented Jun 3, 2017 at 10:33
@Eb1993 can you post the error message? We can take a look at the error and debug. — Luke101
– Luke101, Commented Jun 3, 2017 at 10:41

pbuck · Accepted Answer · 2017-06-03 15:06:13Z

1

You have multiple %s in your initial mtype assignment, yet your execute provides a tuple with only a single parameter. This will fail. This can be fixed by providing the correct number of parameters in execute:

mtype = """SELECT... member_id=%s UNION ... member_id=%s UNION ... member_id=%s"""
cur.execute(mtype, (member_id, member_id, member_id))

Of course, there may be other errors in the code: one shouldn't catch Exceptions blindly unless, really, you don't care what the error is.

answered Jun 3, 2017 at 15:06

pbuck

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Comments

Ritwik G · Accepted Answer · 2017-06-03 14:32:04Z

0

I don't have enough points to make a comment. So posting here. Just saying which line produces error doesn't give a lot of insight into the problem. My advice is either you print what is the error or in case you don't know how to do that, remove the first try catch and see what is the error produced. If you post that people could help you resolve it.

answered Jun 3, 2017 at 14:32

Ritwik G

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