See https://docs.python.org/2/library/collections.html#collections.namedtuple

namedtuple is called as:
collections.namedtuple(typename, field_names[, verbose=False][, rename=False])

So you are passing in
typename = 'Name'
field_names = 'a'
verbose = 'b'
rename = 'c'

'b' is a True value, so that's why it's showing the output.

You want to be using: 
sample = namedtuple('Name', ['a', 'b', 'c'])