On Tue, Jan 14, 2014 at 7:59 AM, Guido van Rossum <gu...@python.org> wrote:
> Here's an example of what I mean:
I sent that off without proofreading, and I also got one detail about
asciistr() wrong. Here are some corrections.
> def spam(a):
> r = asciistr('(')
> if a: r += a.strip()
> r += asciistr(')')
> return r
>
> The argument must be a string.
Or a bytes object. And the point is that the return type should be the
same as the argument type.
> If I call spam(''),
or spam(b'')
> a's type is never concatenated with r, so the
> return value is an asciistr.
Actually, Nick explained that asciistr() + asciistr() returns str, so
this would be accidentally correct if called with '', but wrong
(returning a str instead of a bytes) if called with b''.
> To fix this particular case, we could
> drop the "if a:" part. But it could be more significant, e.g. it could
> be something like "if a contains any digits". The general fix would be
> to add
>
> else: r += a[:0]
>
> but that's still an example of the awkwardness that asciistr() is
> trying to avoid.
This is still valid.
--
--Guido van Rossum (python.org/~guido)
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