TypeNone field detection

[Steve Holden]

Joe Blow wrote:
> What is the best way to detect a TypeNone field in a tuple, or in a list?
> 
> I am accessing a MySQL database using the MySQLdb Python interface... this
> interface returns a tuple object type in response to SQL SELECT
> statements.  My understanding of the MySQLdb interface is that NULL
> database values are returned as a Python 'None' object.
> 
> Because I need to create some work fields based on the contents of the
> database I am doing so by copying the tuple to a list object and then
> calculating these work fields as needed.  My problem is that I need to be
> able to detect the Python 'None' objects and convert them to an integer
> zero value field to enable my calculations to work.
> 
> I'm new to Python so I'm sure I'm overlooking something simple – but what
> is the easiest way to do a logical test for the existence of a TypeNone
> field?

Since there is only one instance of TypeNone (the value we reference as 
None) the easiest test is

   if x is None:

There is no need to create a list first: you can create a list as you 
iterate over the tuple:

a = (1, 2, None, "a", "b")
a = [0 if x is None else x for x in a]

regards
  Steve
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