namedtuple is a tuple so you can iterate as over normal tuple:
>>> from collections import namedtuple
>>> A = namedtuple('A', ['a', 'b'])
>>> for i in A(1,2):
print i
1
2
but tuples are immutable so you cannot change the value
if you need the name of the field you can use:
>>> a = A(1, 2)
>>> for name, value in a._asdict().iteritems():
print name
print value
a
1
b
2
>>> for fld in a._fields:
print fld
print getattr(a, fld)
a
1
b
2