[SciPy-user] fromfile, item, what other output than stdout / stderr is used ?

[Christopher Barker]

Robert Kern wrote:
> But that doesn't let you express, "read at most this number of items,"
> which is really useful and is very common in file-reading APIs.

fair enough --

>> maybe a flag? 

> If it makes you feel better, you may consider the warnings mechanism
> to be just such a flag, only it uses a Python-standard mechanism for
> controlling such behavior.

no, it doesn't -- I don't think warnings are designed for this sort of 
thing.


>>> This lets you either silence
>>> the warning or turn it into an exception depending on your use case.

I've been a pythonista for years, and I have no idea how to turn a 
warning into an exception, and I DID just spend some time trying to 
figure it out -- it does not look easy. Maybe it is, but if it's hard to 
figure out, and it won't dawn on many users that they need to, there 
will be bugs.


I think we agree that fromfile() needs a way to spell:

"read at most this number of items,"

Why not spell that explicitly? we have "count" to specify whether or not 
you want a specific number of items. We could have max_count or 
whatever. I don't care how it's spelled but I do want to be able to 
explicitly spell which I want.

In any case, having the warning printed with C stdout is not ideal.


Pauli Virtanen wrote:
 > Not completely true: if it can't read any items, it either raises
 > MemoryError. Also, for sep != '' it returns read_count+1 items, the 
 >last  one containing junk. A bug, methinks...

right -- for the record, I wasn't guessing, I was recalling problems 
I've had in the past. though I should have tested first.


Anyway, fromfile needs attention -- we've had discussions about it in 
the past, but no one has found the time and inclination to give it the 
attention it needs (including me).

oh well.

-Chris





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