From: Greg Ewing <greg.ewing@compaq.com>
Subject: Re: Why exceptions shouldn't be used for flow control [Re: YAS to the
"Reading line-by-line" Problem]
Organization: Digital Equipment Corporation, Palo Alto, CA, USA
William Tanksley wrote:
>
> while not f.eof():
> line = f.readline()
> # ...
I'd love to be able to write reading loops that way.
Unfortunately, it's a fact of life that some of the
things read() has to deal with are unable to detect
eof without trying to read something. I think the
existing definition of read() and friends is the best
that can be done in those circumstances.
> It's been a while since I've used read, so I
> don't recall what it actually returns
It returns an empty string if it can't read more
than 0 characters, same as readline().
> in a function designed to get n!=0
> more characters, an EOF really is an error. Unfortunately for me, that's
> not the definition of 'read', and never will be.
Perhaps there should be a 2-parameter version of read:
read(min, max)
which would raise an exception if it couldn't read at
least min characters. Setting min=0 would give the
current behaviour, and setting min=max would allow
reading a fixed-length record without having to check
for errors. Then everyone would be happy!
Greg
--
|Fidonet: UUCP 2:500/3.1
|Internet: UUCP@p1.f3.n500.z2.hccfido.hcc.nl
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| Standard disclaimer: The views of this user are strictly his own.
Subject: Re: Why exceptions shouldn't be used for flow control [Re: YAS to the
"Reading line-by-line" Problem]
Organization: Digital Equipment Corporation, Palo Alto, CA, USA
William Tanksley wrote:
>
> while not f.eof():
> line = f.readline()
> # ...
I'd love to be able to write reading loops that way.
Unfortunately, it's a fact of life that some of the
things read() has to deal with are unable to detect
eof without trying to read something. I think the
existing definition of read() and friends is the best
that can be done in those circumstances.
> It's been a while since I've used read, so I
> don't recall what it actually returns
It returns an empty string if it can't read more
than 0 characters, same as readline().
> in a function designed to get n!=0
> more characters, an EOF really is an error. Unfortunately for me, that's
> not the definition of 'read', and never will be.
Perhaps there should be a 2-parameter version of read:
read(min, max)
which would raise an exception if it couldn't read at
least min characters. Setting min=0 would give the
current behaviour, and setting min=max would allow
reading a fixed-length record without having to check
for errors. Then everyone would be happy!
Greg
--
|Fidonet: UUCP 2:500/3.1
|Internet: UUCP@p1.f3.n500.z2.hccfido.hcc.nl
|
| Standard disclaimer: The views of this user are strictly his own.