>>> from functools import reduce
>>> from itertools import chain
>>> from operator import add
>>> def namedtuplemerge(*args):
...     cls = namedtuple('_'.join(arg.__class__.__name__ for arg in args), reduce(add, (arg._fields for arg in args)))
...     return cls(*chain(*args))
...
>>> namedtuplemerge(a, b)
A_B(a=10, b=20, c=30, d=40, e=50)