Draft PEP: string interpolation with backquotes

Christian Tanzer tanzer at swing.co.at
Mon Dec 3 08:08:15 CET 2001


Oren Tirosh <oren-py-l at hishome.net> wrote:

> > >     The expression may be any valid Python expression not containing
> > >     the backquote character.
> > 
> > This is an unnecessary difference with current backtick expressions.  It's
> > not particularly pretty to look at, but nested backtick expressions are
> > unambiguous and work fine.  Artificially restricting them in this context
> > would be a wart (not to mention that you couldn't reuse the compiler code
> > that compiles them now).
> 
> I am aware of this. The reason for this restriction is simplicity.
> String interpolation is meant for short expressions, often just a
> single name. In my proposed implementation most of the processing
> occurs at the tokenizer while parsing nested backtick expressions
> unambigously is a job for the parser so this keeps the implementation
> simple. A possible approach I have considered is to allow nested
> backticks inside interpolations as long as they are surrounded by at
> least one level of parens/braces etc. The tokenizer already counts
> paren levels for expressions extending across newlines.

Did you consider using the $() notation instead of backticks? bash 2.x
supports this and it is much easier to read (in particular when
nested). It also would avoid the overloading of the backticks with two
completely different meanings.

Just my 2c,
Christian

-- 
Christian Tanzer                                         tanzer at swing.co.at
Glasauergasse 32                                       Tel: +43 1 876 62 36
A-1130 Vienna, Austria                                 Fax: +43 1 877 66 92





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