parameters: (f, source)
docstring: alternate write & seek 1000 units
docstring_summary: alternate write & seek 1000 units
docstring_tokens: alternate write & seek 1000 units
function: def modify_seek_forward_blockwise(f, source):
      """ alternate write & seek 1000 units """
      f.seek(0)
      for i in xrange(0, len(source), 2000):
          f.write(source[i:i+1000])
          f.seek(i+2000)
function_tokens: def modify_seek_forward_blockwise ( f , source ) : f . seek ( 0 ) for i in xrange ( 0 , len ( source ) , 2000 ) : f . write ( source [ i : i + 1000 ] ) f . seek ( i + 2000 )