[pypy-issue] Issue #2750: array resize through slice assignment slow (pypy/pypy)

[Christoph Reiter]

New issue 2750: array resize through slice assignment slow
https://bitbucket.org/pypy/pypy/issues/2750/array-resize-through-slice-assignment-slow

Christoph Reiter:

```
#!python

import array

def x(n):
    data = array.array('B')
    for i in range(n):
        data[i:i+1] = array.array("B", [0])

x(20000)
```

With CPython the time per assignment with increasing "n" stays constant, while in PyPy it increases with "n".

There is no real use case behind this, as I can easily preallocate the array which makes things work. I just noticed that one of my test cases got stuck under pypy because it resized an array 100000 times, and with CPython this was near instant.