Eric Smith wrote:
> Ron Adam wrote:
>>
>> Martin v. Lo"wis wrote:
>>> Bill Janssen schrieb:
>>>>> I think most of these points are irrelevant. The curly braces are not
>>>>> just syntactic sugar, at least the opening brace is not; the digit
>>>>> is not syntactic sugar in the case of message translations.
>>>> Are there "computation of matching braces" problems here?
>>> I don't understand: AFAIK, the braces don't nest, so the closing
>>> brace just marks the end of the place holder (which in the printf
>>> format is defined by the type letter).
>
>> So expressions like the following might be difficult to spell.
>>
>> '{{foo}{bar}}'.format(foo='FOO', bar='BAR', FOOBAR = "Fred")
>>
>> This would probably produce an unmatched brace error on the first '}'.
>
> Ah, I see. I hadn't thought of that case. You're correct, it gives an
> error on the first '}'. This is a case where allowing whitespace would
> solve the problem, sort of like C++'s "< <" template issue (which I
> think they've since addressed). I'm not sure if it's worth doing, though:
>
> '{ {foo}{bar} }'.format(foo='FOO', bar='BAR', FOOBAR = "Fred")
>
> On second thought, that won't work. For example, this currently doesn't
> work:
> '{0[{foo}{bar}]}'.format({'FOOBAR': 'abc'}, foo='FOO', bar='BAR')
> KeyError: 'FOO'
>
> I can't decide if that's a bug or not.
I think if we escaped the braces with '\' it will work nicer.
I used the following to test the idea and it seems to work and should
convert to C without any trouble. So to those who can say, would something
like this be an ok solution?
def vformat(self, format_string, args, kwargs):
# Needs unused args check code.
while 1:
front, field, back = self._get_inner_field(format_string)
if not field:
break
key, sep, spec = field.partition(':')
value = self.get_value(key, args, kwargs)
result = self.format_field(value, spec)
format_string = front + result + back
return format_string.replace('\{', '{').replace('\}', '}')
def _get_inner_field(self, s):
# Get an inner most field from right to left.
end = 0
while end < len(s):
if s[end] == '}' and not self._is_escaped(s, end, '}'):
break
end += 1
if end == len(s):
return s, '', ''
start = end - 1
while start >= 0:
if s[start] == '{' and not self._is_escaped(s, start, '{'):
break
start -= 1
if start < 0:
raise(ValueError, "missmatched braces")
return s[:start], s[start+1:end], s[end+1:]
def _is_escaped(self, s, i, char):
# Determine if the char is escaped with '\'.
if s[i] != char or i == 0:
return False
i -= 1
n = 0
while i >= 0 and s[i] == '\\':
n += 1
i -= 1
return n % 2 == 1
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