[Zope] python script and dealing with NULL parameter

[Laura McCord]

Thanks Tino,

if notes is None:
 notes = 'none'
else:
 notes=notes[0:35]
return notes

Using None worked. There are still some keywords and functions in python
that I am still learning.

Thanks Again,
 Laura

-----Original Message-----
From: Tino Wildenhain [mailto:tino at wildenhain.de] 
Sent: Friday, October 15, 2004 1:44 PM
To: Laura McCord
Cc: zope at zope.org
Subject: Re: [Zope] python script and dealing with NULL parameter


Hi,

Am Fr, den 15.10.2004 schrieb Laura McCord um 20:24:
> I noticed that when the parameter is Null I get a Type Error 
> Unsubscriptable object. Is there a python function or an if statement 
> that will fix this?

There is no "null" in Python. The equivalence to that
(and I suspect you are talking about this) is None.
Usually database adaptors map SQL "null" to Python None.

In python you have: 
is None
==None
to check.
In most situations, boolean algebra is more convient:

None, "", '', {}, (), [] and so on are logically "false".

if maybe_none:  will only used if true or not one of the above values

also:

maybe_none or "defaultvalue"  is usefull if you like
functional programming (list comprehensions for example)


(value is None and "No pricetag") or ("$ %0.2f" % value)

would be an expression for full functional programming using boolean
algebra :-) (try it out with different values from python command line)


Regards
Tino