mapping None values to ''

[micklee74 at hotmail.com]

hi
i wish to map None or "None" values to "".
eg
a = None
b = None
c = "None"

map( <something>  ,  [i for i in [a,b,c] if i in ("None",None) ])

I can't seem to find a way to put all values to "". Can anyone help?
thanks