python - How to stop iterating using itertools.islice when EOF is reached -

i use itertools.islice(self._f, 0, 100, none) read in file piece piece (in blocks of 100 lines) follows:

f = open('test.dat', 'r')  while (some condition for):     f = open(filename, 'r')       x = itertools.islice(f, 0, 100, none)      dosomethingwithx(x) 

my problem is, not know how long file , looking condition stop while loop when end of file reached. cannot figure out how done.

edit: ok, see difficulty. maybe should reformulate question when itertools.islice capsuled in class here:

class reader:     def __init__()         self._f = open('test.dat', 'r')      def getnext():         return itertools.islice(self._f, 0, 100, none)     r = reader() while (some condition for):    x = r.getnext()    dosomethingwithx(x) 

if don't mind getting list slices, can use iter:

with  open(filename, 'r')  f:     x in iter(lambda: list(itertools.islice(f, 100)), []):         dosomethingwithx(x) 

not sure file using have f = .. twice , have self_.f in there too.

using edited code:

class reader:     def __init__(self):         self._f = open('out.csv', 'r')      def getnext(self):         return itertools.islice(self._f, 100)  r = reader() import itertools x in iter(lambda: list(r.getnext()),[]):     print(x) 

using test file following , class code using itertools.islice(self._f, 2):

1 2 3 4 5 6 7 8 9 10 

outputs:

in [15]: r = reader()  in [16]: import itertools  in [17]: x in iter(lambda: list(r.getnext()),[]):    ....:         print(x)    ....:      ['1\r\n', '2\r\n'] ['3\r\n', '4\r\n'] ['5\r\n', '6\r\n'] ['7\r\n', '8\r\n'] ['9\r\n', '10']