Classes and global statements

[Scott David Daniels]

Sheldon wrote:
> Hi,
> 
> I have a series of classes that are all within the same file. Each is
> called at different times by the main script. Now I have discovered
> that I need several variables returned to the main script. Simple,
> right? I thought so and simply returned the variables in a tuple:
> (a,b,c,d,e) = obj.method()
> Now I keep getting this error: "ValueError: unpack tuple of wrong size"
What you need to do at this point is read the _whole_ error message
(including the ugly traceback stuff).  Think hard about what is going
on.  "ValueError: unpack tuple of wrong size" comes from returning
a tuple of a different size than your assignment is producing:

     def triple(v):
         return v, v*v

     x, y, z = triple(13)

Break up the assignment and insert prints:

     # x, y, z = triple(13)
     temp = triple(13)
     print "I'm going to expand the triple:", temp
     x, y, z = temp


>  I think this is because I am trying to return some Numeric arrays as
> well as list and I didn't declare these prior to calling the class
> method. 
Don't guess and hypothesize; create experiments and test.  Your
reasoning is off in the ozone.  You waste a lot of time creating
great theories; make tiny theories and _test_ them.

<<and the theories wander farther and farther off into the weeds>>

--Scott David Daniels
scott.daniels at acm.org