SQLite output from query into Python script

Question

I have this Python script:

s = stdscr.getstr(0,0, 20) #input length last number
            c = db.execute("""SELECT "debit" FROM "members" WHERE "barcode" = '%s' LIMIT 1""" % (s,))
            for row in c:
                    print row

                    if row == '(0,)':
                            #display cross
                            print 'Tick'
                    else:
                            #display tick
                            print 'Cross'

Where it is asking for a barcode input, and matching the debit field in the database.

The "print row" command returns "(0,)" but when I try to match it, I always get "Cross" as the output, which is not the intended result. Is there a semantic I'm obviously not observing?

Many thanks!

damienfrancois · Accepted Answer · 2014-09-08 07:27:36Z

1

The variable row is a tuple, and '(0,)' is its string representation. Your are comparing a variable with its string representation, which cannot work.

You need to compare it to the tuple value

if row == (0,):

Simply remove the quote marks.

Alternatively, you can write

if row[0] == 0:

which will avoid the creation of a tuple just for the comparison. As noted by @CL., row will never be an empty tuple so extracting row[0] is safe.

edited Sep 8, 2014 at 7:27

answered Sep 7, 2014 at 21:10

damienfrancois

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3 Comments

CL. Over a year ago

Wouldn't row[0] == 0 be better?

damienfrancois Over a year ago

@CL. The disadvantage I see is that you need then to catch IndexError: tuple index out of range then. But maybe execute will never return an empty tuple in this case. Am I missing something? Do you see a clear advantage to your approach?

CL. Over a year ago

The value might be NULL, but it will always be there.

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