On 2023-04-26 02:16, Joao S. O. Bueno wrote:
On Sat, Apr 22, 2023 at 10:06 AM Damian Cross <damnedbo...@gmail.com
<mailto:damnedbo...@gmail.com>> wrote:
That would have the effect that every use of str.format for everyone
would start producing partially-formatted strings if an argument is
accidentally omitted instead of raising an error. Some people might
not like that.
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If that is all there is for a downside, this is actually quite weak. You
just changed my mind to +1 on the proposal.
Worst case scenario, one goes from one non-running program to a running
program producing partially incorrect output. Any legacy code that was
not working in the first place, is obviously, clearly, not critical for
anyone, otherwise it would have been fixed already.
We can't stal all augmenting to language functionalities because "some
is used with the fact writing incorrect code in this way used to produce
an error before". Ultimately, by this logic, it would be impossible to
add even any new keyword only parameters to any stdlib call, because
"there might be some code out there using this parameter, and that used
to raise an error"
The problem is that the resulting string might or might not be fully
formatted, but you wouldn't be sure.
The original post itself almost demonstrates the issue. I say "almost"
because it has:
>>> r"\mathjax{{color}}{{text}}".format(color="blue", text="Spanish")
which is '\\mathjax{color}{text}', not "\\mathjax{blue}{Spanish}",
because "{{" and "}}" are literals.
After correction:
>>> pfr = r"\mathjax{{{color}}}{{{text}}}".format(color="blue")
So, pfr == r"\mathjax{blue}{{{text}}}".
That looks like a format string with 2 placeholders, "{blue}" and "{text}".
And what happens if the partially-formatted string isn't a valid format
string?
So I'm -1 on the idea.
You'd be better off creating a new Format class that parses a format
string and lets you insert values:
>>> fmt = Format(r"\mathjax{{{color}}}{{{text}}}")
>>> fmt
Format('\\mathjax{{{color}}}{{{text}}}')
(Calling it "Format" has the disadvantage that it's too close to the
build-in function "format".)
Placeholders can be positional or named, which is like the arguments of
function calls, so maybe it's a callable:
>>> fmt = fmt(color="blue")
>>> fmt
Format('\\mathjax{{{color}}}{{{text}}}', color='blue')
>>> fmt = fmt(text="Spanish")
>>> fmt
Format('\\mathjax{{{color}}}{{{text}}}', color='blue', text='Spanish')
>>> str(fmt)
'\\mathjax{blue}{Spanish}'
>>> print(fmt)
\mathjax{blue}{Spanish}
The advantages of leaving it as a format each time are 1) it can ignore
unneeded values and 2) it consistently returns an instance of the same type.
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