[Numpy-discussion] fromfile and ticket #1152

[Pauli Virtanen]

On 2009-06-27, Jed Ludlow <jed.ludlow at gmail.com> wrote:
> Of course, this discussion isn't new, and I don't know that it needs to be
> completely rehashed.  See
>
> http://mail.scipy.org/pipermail/numpy-discussion/2009-May/042668.html

Especially this: 

	http://mail.scipy.org/pipermail/numpy-discussion/2009-May/042762.html

I think we sort of converged on some aspects of viable interface 
options:

- "Non-strict" interface

  Return as many items as can be read, or up to `count`, if given.
  Never raise errors or warnings. Stop reading immediately on
  unexpected input.

  fromstring("1,2,x,4", sep=",") -> [1,2]
  fromstring("1,2,x,4", sep=",", count=5) -> [1,2]

- Strict interface

  Raise ValueError on malformed input, or if there are not 
  enough items for `count`.

  fromstring("1,2,x,4", sep=",") -> ValueError
  fromstring("1,2,3,4", sep=",", count=5) -> ValueError

The main disagreement was which of the above to use as the 
default.

A hybrid of the above, which would raise an error only when 
`count` was specified, was also suggested.

Then some variations on whether default values should be 
introduced and what to do with non-numeric entries in this case.

I believe:

- We should not break backward compatibility, so the "non-strict" interface
  should be the default.

  No errors or warnings raised, except passing through underlying
  I/O errors (eg. sector not found and other OS-level stuff).

- We could optionally, later on, implement the strict interface.

- We should drop the idea of default values for now, and 
  keep fromfile and fromstring simple.

[clip]
> I would vote toward harmonizing the behavior with the python built-in
> fid.read(bytes) as the default, which simply returns as many items as could be
> read before the EOF was reached, including zero.  An additional strict interface
> could be added (by keyword) for those who want an exception raised whenever the
> requested read count could not be completed.

+1

-- 
Pauli Virtanen