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
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Re: getting an empty tuple
On 31 Jul 2005 08:40:26 -0700, [EMAIL PROTECTED] [EMAIL PROTECTED] 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. -- http://mail.python.org/mailman/listinfo/python-list
Re: getting an empty tuple
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 ')
# 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.
--
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Re: getting an empty tuple
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 ')
# 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.
--
http://mail.python.org/mailman/listinfo/python-list
