$ ipython
c:\python34\lib\site-packages\win_unicode_console\__init__.py:31: RuntimeWarning: sys.stdin.encoding == 'cp65001', whereas sys.stdout.encoding == 'utf-8', readline hook consumer may assume they are the same
  readline_hook.enable(use_pyreadline=use_pyreadline)
Python 3.4.3 (v3.4.3:9b73f1c3e601, Feb 24 2015, 22:44:40) [MSC v.1600 64 bit (AMD64)]
Type "copyright", "credits" or "license" for more information.

IPython 5.0.0 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.

In [1]: import numpy as np

In [2]: vv = np.ones((1000, 1000), dtype=str)

In [3]: @np.vectorize
   ...: def append(*args):
   ...:     return ''.join(args)
   ...:

In [4]: %timeit append("file", vv, ".txt")
1 loop, best of 3: 835 ms per loop

In [5]: