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# getting an empty tuple

Hey there,
i have a simple database query that returns as a tuple the number of
rows that the query selected.
kinda like this
cursor.execute( 'select value from table where autoinc > 234')
x = cursor.fetchall ()
print x 21L
ok, means 21 rows met the criteria of the query. but if there are none
that match,
like i do a
print x
0L

how do i encorporate that into an equation ?
i have tried all kinds of stuff

if x == 0L
if x(0) == None
if x == None

anyway, what shoud i do to test if the result is empty?

thanks

Jul 31 '05 #1
3 4864
On 31 Jul 2005 08:40:26 -0700, ne*****@xit.net <ne*****@xit.ne t> wrote:
how do i encorporate that into an equation ?
i have tried all kinds of stuff

if x == 0L
if x(0) == None
if x == None

anyway, what shoud i do to test if the result is empty?

Just like any other test:

if not x:

--

# p.d.
Jul 31 '05 #2
On Sun, 31 Jul 2005 08:40:26 -0700, nephish wrote:
Hey there,
i have a simple database query that returns as a tuple the number of
rows that the query selected.
kinda like this
cursor.execute( 'select value from table where autoinc > 234')
x = cursor.fetchall ()
print x 21L

21L is not a tuple, it is a long integer.
ok, means 21 rows met the criteria of the query. but if there are none
that match,
like i do a
print x
0L

how do i encorporate that into an equation ?
i have tried all kinds of stuff

And did they work? If they didn't work, tell us the exact error message
you got.

if x == 0L
If x is a long integer, then that will work. Of just "if x == 0:" will
work too.

if x(0) == None
No. That means x is a function, and you are giving it an argument of 0,
and it returns None.
if x == None
You said that your query returns a tuple, but then gave an example where
it returns a long int. None is not a tuple, nor a long int, so testing
either of those things against None will never be true.

Did you try any of these things in the interactive interpreter? Python is
a great language for experimenting, because you can try this yourself:

# run your setup code ...
# and then do some experimenting
cursor.execute( 'select value from table where autoinc > 99999999')
# or some value that will never happen
x = cursor.fetchall ()
print x

What do you get?

anyway, what shoud i do to test if the result is empty?

Long ints are never empty, but they can be zero:

if x == 0:
print "no rows were found"
elif x == 1:
print "1 row was found"
else:
print "%d rows were found" % x

Tuples can be empty:

if len(x) == 0:
print "no rows were found"

or if you prefer:

if x == ():
print "no rows were found"
But the cleanest, most Pythonic way is just to do a truth-test:

if x:
print "something was found"
else:
print "x is empty, false, blank, nothing..."
--
Steven.

Jul 31 '05 #3
ok, this is what works:
if x == ():

sorry about the bad info. and what i ment to put was
x[0] not x(0)

thanks for the tips
its all good now

shawn
Steven D'Aprano wrote:
On Sun, 31 Jul 2005 08:40:26 -0700, nephish wrote:
Hey there,
i have a simple database query that returns as a tuple the number of
rows that the query selected.
kinda like this
> cursor.execute( 'select value from table where autoinc > 234')
> x = cursor.fetchall ()
> print x

> 21L

21L is not a tuple, it is a long integer.
ok, means 21 rows met the criteria of the query. but if there are none
that match,
like i do a
> print x
> 0L

how do i encorporate that into an equation ?
i have tried all kinds of stuff

And did they work? If they didn't work, tell us the exact error message
you got.

if x == 0L

If x is a long integer, then that will work. Of just "if x == 0:" will
work too.

if x(0) == None

No. That means x is a function, and you are giving it an argument of 0,
and it returns None.
if x == None

You said that your query returns a tuple, but then gave an example where
it returns a long int. None is not a tuple, nor a long int, so testing
either of those things against None will never be true.

Did you try any of these things in the interactive interpreter? Python is
a great language for experimenting, because you can try this yourself:

# run your setup code ...
# and then do some experimenting
cursor.execute( 'select value from table where autoinc > 99999999')
# or some value that will never happen
x = cursor.fetchall ()
print x

What do you get?

anyway, what shoud i do to test if the result is empty?

Long ints are never empty, but they can be zero:

if x == 0:
print "no rows were found"
elif x == 1:
print "1 row was found"
else:
print "%d rows were found" % x

Tuples can be empty:

if len(x) == 0:
print "no rows were found"

or if you prefer:

if x == ():
print "no rows were found"
But the cleanest, most Pythonic way is just to do a truth-test:

if x:
print "something was found"
else:
print "x is empty, false, blank, nothing..."
--
Steven.

Jul 31 '05 #4

This thread has been closed and replies have been disabled. Please start a new discussion.

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