Possible bug with TypeError in Python

Aaron Konstam akonstam at sbcglobal.net
Wed Jan 30 14:21:27 UTC 2008


On Wed, 2008-01-30 at 19:34 +0530, Anoop Chandran wrote:
> 
> 
> On Jan 30, 2008 7:28 PM, Mark C. Allman <mcallman at allmanpc.com> 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.

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.

--
=======================================================================
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
=======================================================================
Aaron Konstam telephone: (210) 656-0355 e-mail: akonstam at sbcglobal.net




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