How to validate the __init__ parameters

[Gabriel Genellina]

En Mon, 04 Jan 2010 15:17:04 -0300, Albert van der Horst  
<albert at spenarnc.xs4all.nl> escribió:

> This triggers a question: I can see the traceback, but it
> would be much more valuable, if I could see the arguments
> passed to the functions. Is there a tool?

Yes, the cgitb module [1]. Despite its name it's a general purpose module.  
This code:

<code>
import cgitb
cgitb.enable(format="text")

spam = []

def a(x, y):
   """This is function a"""
   z = x+y
   return b(z)


def b(z, n=3):
   """This is function b"""
   return c(foo=z*n)


def c(foo=0, bar=1):
   """This is function c"""
   baz = foo+bar
   spam.somenamethatdoesnotexist(foo+bar)


a(10, 20)
<code>

generates this error message:

A problem occurred in a Python script.  Here is the sequence of
function calls leading up to the error, in the order they occurr
ed.

  d:\temp\test_traceback.py in <module>()
    19   baz = foo+bar
    20   spam.somenamethatdoesnotexist(foo+bar)
    21
    22
    23 a(10, 20)
a = <function a at 0x00BFEBB0>

  d:\temp\test_traceback.py in a(x=10, y=20)
     7   """This is function a"""
     8   z = x+y
     9   return b(z)
    10
    11
global b = <function b at 0x00BFEBF0>
z = 30

  d:\temp\test_traceback.py in b(z=30, n=3)
    12 def b(z, n=3):
    13   """This is function b"""
    14   return c(foo=z*n)
    15
    16
global c = <function c at 0x00BFEC30>
foo undefined
z = 30
n = 3

  d:\temp\test_traceback.py in c(foo=90, bar=1)
    18   """This is function c"""
    19   baz = foo+bar
    20   spam.somenamethatdoesnotexist(foo+bar)
    21
    22
global spam = []
spam.somenamethatdoesnotexist undefined
foo = 90
bar = 1
<type 'exceptions.AttributeError'>: 'list' object has no attribu
te 'somenamethatdoesnotexist'
     __class__ = <type 'exceptions.AttributeError'>
     __dict__ = {}
     __doc__ = 'Attribute not found.'
     ... more exception attributes  ...

The above is a description of an error in a Python program.  Her
e is
the original traceback:

Traceback (most recent call last):
   File "d:\temp\test_traceback.py", line 23, in <module>
     a(10, 20)
   File "d:\temp\test_traceback.py", line 9, in a
     return b(z)
   File "d:\temp\test_traceback.py", line 14, in b
     return c(foo=z*n)
   File "d:\temp\test_traceback.py", line 20, in c
     spam.somenamethatdoesnotexist(foo+bar)
AttributeError: 'list' object has no attribute 'somenamethatdoes
notexist'

[1] http://docs.python.org/library/cgitb.html

-- 
Gabriel Genellina