create an iterator that print each character in a file until it returns

create an iterator that print each character in a file
until it returns '\n'.
#create an iterator that calls f.read(1) until it returns '\n'.
#syntax:   iter(callable, sentinel) -> iterator;
the callable is called until it returns the sentinel

def next_line(f):
  for c in iter(lambda: f.read(1),'\n'):
      print "------->", c

fp = open('test_file', 'r')

next_line(fp)

#Suppose file 'test_file' contain line 'hello'

Output
=====
------->h
------->e
------->l
------->l
------->o