At the moment it is very silent on Python-dev. I guess you guys are
all out hunting dead parrots, which escaped from the cages on April 1st. ;-)
So this might be the right moment to present a possibly bad idea (TM).
see below.
Regards, Peter
--
Peter Funk, Oldenburger Str.86, D-27777 Ganderkesee, Germany, Fax:+49 4222950260
office: +49 421 20419-0 (ArtCom GmbH, Grazer Str.8, D-28359 Bremen, Germany)
PEP: XXXX
Title: String Scanning
Version: $Revision$
Author: pf@artcom-gmbh.de (Peter Funk)
Status: Not yet Draft
Type: Standards Track
Python-Version: 2.2
Created: 02-Apr-2001
Post-History:
Abstract
This document proposes a string scanning feature for Python to
allow easier string parsing. The suggested syntax change is to
allow the use of the division '/' operator for string operands
as counterpart to the already existing '%' string interpolation
operator. In current Python this raises an exception: 'TypeError:
bad operand type(s) for /'. With the proposed enhancement the
expression string1 / format2 should either return a simple value,
a tuple of values or a dictionary depending on the content of
the right operand (aka. format) string.
Copyright
This document is in the public domain.
Specification
The feature should mimic the behaviour of the scanf function
well known to C programmers. For any format string sf and any
matching input string si the following pseudo condition should
be true:
string.split( sf % (si / sf) ) == string.split( si )
That is modulo any differences in white space the result of the
string interpolation using the intermediate result from the string
scanning operation should look similar to original input string.
All conversions are introduced by the % (percent sign) character.
The format string may also contain other characters. White space
(such as blanks, tabs, or newlines) in the format string match any
amount of white space, including none, in the input. Everything
else matches only itself. Scanning stops when an input character
does not match such a format character. Scanning also stops when
an input conversion cannot be made (see below).
Examples
Here is an example of an interactive session exhibiting the
expected behaviour of this feature.
>>> "12345 John Doe" / "%5d %8s"
(12345, 'John Doe')
>>> "12 34 56 7.890" / "%d %d %d %f"
(12, 34, 56, 7.8899999999999997)
>>> "12345 John Doe, Foo Bar" / "%(num)d %(n)s, %(f)s %(b)s"
{'n': 'John Doe', 'f': 'Foo', 'b': 'Bar', 'num': 12345}
>>> "1 2" / "%d %d %d"
Traceback (innermost last):
File "<stdin>", line 1, in ?
TypeError: not all arguments filled
Discussion
This should fix the assymetry between arithmetic types and strings.
It should also make the life easier for C programmers migrating to
Python (see FAQ 4.33). Those poor souls are acustomed to scanf
as the counterpart of printf and usually feel uneasy to convert
to string slitting, slicing or the syntax of regular expressions.
Security Issues
There should be no security issues.
Implementation
There is no implementation yet. This is just an idea.
Local Variables:
mode: indented-text
indent-tabs-mode: nil
End:
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