To get a list of myData tuples, do:
data = map(myData._make, reader) # or [myData._make(r) for r in reader]
To get all the values of a particular field:
from operator import attrgetter
data_divs = map(attrgetter('div'), data) # or [r.div for r in data]
However, if you're concerned about efficiency, you should be aware that using attribute access with namedtuples is several times slower than indexed access. This will be faster:
from operator import itemgetter
div_idx = myData._fields.index('div')
data_divs = map(itemgetter(div_idx), data) # or [r[div_idx] for r in data]
Both produce the same list of values.