Newbie: Struggling again 'map'

[mosscliffe]

I thought I had the difference between 'zip' and 'map' sorted but when
I try to fill missing entries with something other than 'None'. I do
not seem to be able to get it to work - any pointers appreciated.

Richard

lista = ['a1', 'a2']
listb = ['b10', 'b11','b12' ,'b13']

for x,y in zip(lista, listb):    #  Fine Truncates as expected
    print "ZIP:", x, "<<x  y>>", y

for x,y in map(None, lista, listb):  #  Also fine - extends as
expected
    print "MAP:", x, "<<x  y>>", y

for x,y in map("N/A", lista, listb): ########## Fails - Can not call a
'str'
    print "MAP:", x, "<<x  y>>", y

def fillwith(fillchars):
    return fillchars

for x,y in map(fillwith("N/A"), lista, listb): ########## Fails also -
Can not call a 'str'
    print "MAP:", x, "<<x  y>>", y