Greg Ewing writes:
> On 20/09/20 7:45 am, Christopher Barker wrote:
> > In [4]: from parse import parse
> > In [5]: parse("{x}{y}{z}", a_string)
> > Out[5]: <Result () {'x': '2', 'y': '3', 'z': '4567'}>
> >
> > In [6]: parse("{x:d}{y:d}{z:d}", a_string)
> > Out[6]: <Result () {'x': 2345, 'y': 6, 'z': 7}>
> >
> > So that's interesting -- different level of "greadiness" for strings
> > than integers
>
> Hmmm, that seems really unintuitive. I think a better result would
> be a parse error -- "I was told to expect three things, but I only
> found one."
Are you sure that shouldn't be "I was told to expect three things, but
I found six?" ;-)
And why not parse a_string using the "grammar" "{x}{y}{z}" as {'x':
2345, 'y': 6, 'z': 7}? That's perfectly valid *interpreting the
'grammar' as a format string", and therefore might very well be
expected. Of course there's probably a rule in parse that {x} is an
abbreviation for {x:s}.
Regexps are hard for people to interpret, but they're well-defined and
one *can* learn them. If we're going to go beyond regexps in the
stdlib (and I'm certainly in favor of that!), let's have a parser that
uses a grammar notation that is rarely ambiguous in the way that
format strings *usually* are, and when there is ambiguity, demands
that the programmer explicitly disambiguate rather than "guessing" in
some arbitrary way.
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