Python sqlalchemy update row with variable issues

Question

I am trying to update an sqlalchemy database. It throws an error based off the string I try to implement into the query. I dont want to hardcode the link, but rather use the variable as I am looping through my database.

print (u)
(u'http://32rfckwuorlf4dlv.ca/linklist/1-general\n',)


currentlink = (str(u)[:-3][1:])
print currentlink
u'http://32rfckwuorlf4dlv.ca/linklist/1-general\n'

This fails..

x = Item.query.filter_by(link=currentlink).first()
            print x
            try:
                print x.id
                x.title = 'test'
            except Exception as e:
                print(str(e))

            db.session.commit()

prints :'NoneType' object has no attribute 'id'

This works..

x =  Item.query.filter_by(link=u'http://32rfckwuorlf4dlv.ca/linklist/1-general\n').first()

            print x
            try:
                print x.id
                x.title = 'test'
            except Exception as e:
                print(str(e))

            db.session.commit()

prints: http://32rfckwuorlf4dlv.ca/linklist/1-general\n'> prints: 90

Well yea there's a row in your database with link = 'http://32rfckwuorlf4dlv.ca/client-check\n' but no row with link = 'http://32rfckwuorlf4dlv.ca/linklist/1-general\n'. — univerio
– univerio, Commented May 24, 2016 at 1:39
Used wrong link example..i believe it has to do with the way \n is represented. — Anekdotin
– Anekdotin, Commented May 24, 2016 at 1:43

univerio · Accepted Answer · 2016-05-24 01:53:20Z

1

Okay the reason is that currentlink is actually "u'http://32rfckwuorlf4dlv.ca/linklist/1-general\\n", not u'http://32rfckwuorlf4dlv.ca/linklist/1-general\n'.

Assuming u is a tuple, you should do

currentlink = u[0]

instead.

If you want to make your example work (not recommended by the way, it's only for edification purposes):

currentlink = str(u)[:-3][3:].replace("\\n", "\n")

If u is a str instead, you need to figure out why it's a str instead of a tuple.

edited May 24, 2016 at 1:53

answered May 24, 2016 at 1:47

univerio

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tntC4stl3 · Accepted Answer · 2016-05-24 01:47:11Z

1

two things

seems the variable u in your description is a tuple, so you can just use currentlink = u[0] to get the url link.
The currentlink u'http://32rfckwuorlf4dlv.ca/linklist/1-general\n' and http://32rfckwuorlf4dlv.ca/client-check\n in hardcode are different. And I think this is the reason that you get a Nonetype from database.

answered May 24, 2016 at 1:47

tntC4stl3

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