[Python-Dev] PEP 460: allowing %d and %f and mojibake (original) (raw)

Guido van Rossum guido at python.org
Tue Jan 14 18:58:32 CET 2014

On Tue, Jan 14, 2014 at 7:59 AM, Guido van Rossum <guido at 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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