from itertools import dropwhile
with open('/etc/passwd') as f:
... for line in dropwhile(lambda line: line.startswith('#'), f):
... print(line, end='')

from itertools import chain
>>> a = [1, 2, 3, 4]
>>> b = ['x', 'y', 'z']
>>> for x in chain(a, b):
... print(x)

from functools import partial
RECORD_SIZE = 32
with open('somefile.data', 'rb') as f:
records = iter(partial(f.read, RECORD_SIZE), b'')
for r in records:
...