Aaron Konstam wrote:
On Wed, 2008-01-30 at 19:34 +0530, Anoop Chandran wrote:
On Jan 30, 2008 7:28 PM, Mark C. Allman <mcallman@xxxxxxxxxxxx> wrote:
On Wed, 2008-01-30 at 07:40 -0600, Aaron Konstam wrote:
> The following seems like an bug in python in both f7 and f8
but I would
> like input before I post a bugzilla. It seems the exception
handler
> cannot trap the TypeError in python.
> For example:
> def plus(a,b):
> try:
> return(a+b)
> except TypeError:
> return None
>
> If we define plus as above and call it with: plus(3,) we
should get
> nothing returned. Instead we get:
> Traceback (most recent call last):
> File "./calculator", line 47, in <module>
> exec("register=op[tokens[0]](register)")
> File "<string>", line 1, in <module>
> TypeError: plus() takes exactly 2 arguments (1 given)
>
> This seems like a bug. An ideas out there?
> --
>
If I remember right, the exception is occurring before the
actual call
into "plus()." Try:
plus(3,"My String");
and you should see the TypeError.
try:
a = plus(3)
except TypeError:
a = 0
print a
Output should be 0.
You are both correct but it still seems like a bug. Until you try to
execute plus the system does not know that plus requires 2 arguments.
But nevertheless a TypeError is generated so the exception handler
should be triggered.
The exception is generated while calling plus (as said before) so
before your try/except. So its thrown right back at you and not caught.
But you have given me further insight into the problem so I thank you
all for that insight.
The question is how do I do what I want to do; that is, check that the number
of arguments to plus are correct? In the program in which I am using this
construction the function executed and the arguments are generated dynamically
so doing this checking is necessary.
Using default values might do the trick for you.
>>> def plus(a=None, b=None):
... try:
... return a+b
... except:
... return None
...
>>> print plus(3, )
None
>>> print plus(3)
None
>>> print plus(3,2)
5
Good luck
Daniel
--
=======================================================================
Whether weary or unweary, O man, do not rest, Do not cease your
single-handed struggle. Go on, do not rest. -- An old Gujarati hymn
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Aaron Konstam telephone: (210) 656-0355 e-mail: akonstam@xxxxxxxxxxxxx
