[Tutor] data validation logic

[Alan Gauld]

"Rance Hall" <ranceh at gmail.com> wrote

> I'd like to define a datavalidation function that returns true if 
> data
> is valid, and false if it isn't.
>
>
> Here is the clincher.  the logic of the data validator needs to be
> able to handle different types of data testing on request.
>

This is a good candidate for a factory function which takes
a function as a parameter. The function can be applied to
the data and the resultant function returned as the validator
used by your code. Something like(untested):

def makeValidator(operator, validValues)
     def validator(data, vals = validValues):
           return operator(data, vals)
     return validator

validLowFloat = makeValidator(lambda d,v: type(d) == float and v[0] < 
d < v[1],
                                             (0.0,10.0))

validChoice = makeValidator(lambda d,v: type(d) == str and d.lower() 
in v, ("yes", "no"))

x = 12.0
print validLowFloat(x)   # returns False
y = 7.4
print validLowFloat(y)   # returns True
s = "Maybe"
print validChoice(s)        # -> False
print validChoice("No")    # -> True


If you really want to get clever you could probably wrap
this as a decorator!

Whether its worth the effort over just defining validators as needed
is another matter...

HTH,

-- 
Alan Gauld
Author of the Learn to Program web site
http://www.alan-g.me.uk/