Aaron Brady wrote:
On Dec 21, 10:31 am, MRAB <goo...@mrabarnett.plus.com> wrote:
Aaron Brady wrote:
On Dec 20, 8:49 pm, MRAB <goo...@mrabarnett.plus.com> wrote:
Aaron Brady wrote:
On Dec 20, 7:38 pm, Steven D'Aprano <st...@remove-this-
cybersource.com.au> wrote:
Instead of just whinging, how about making a suggestion to fix it? Go on,
sit down for an hour or ten and try to work out how a BINARY OPERATOR
like % (that means it can only take TWO arguments) can deal with an
arbitrary number of arguments, *without* having any special cases.
Go on. Take your time. I'll be waiting.
Hi, not to take sides, but, there is a possibility.
This behavior is currently legal:
"%i %%i" % 0 % 1
'0 1'
So, just extend it. (Unproduced.)
"%i %i" % 0 % 1
'0 1'
"%r %i" % (2, 3, 4) % 1
'(2, 3, 4) 1'
"%r %i" % (2, 3, 4)
'(2, 3, 4) %i'
Which is quite clever and way ahead of its (posessive) time.
A couple of problems:
1. How do you handle a literal '%'? If you just double up then you'll
need to fix the string after all your substitutions.
2. What if a substitution introduces a '%'?
I suppose a possible solution would be to introduce a special format
string, including a literal, eg:
f"%r %i" % (2, 3, 4) % 1
and then convert the result to a true string:
print(str(f"%r %i" % (2, 3, 4) % 1))
(although print() would call __str__ anyway).
The format string would track where the last substitution occurred.
Hmm... I think I'll just learn the new method. :-)
Now that I'm fighting 'r's war for him/her...
Um, here's one possibility. On the first interpolation, flags are
noted and stored apart from subsequent interpolations. Then, use a
sentinel to terminate the interpolation. (Unproduced.)
"%r %i" % ( 2, 3 ) % 0
'(2, 3) 0'
"%% %r" % ( 2, 3 ) % str.interp_end
'% (2, 3)'
"%sss%i" % "%d" % 0
'%dss0'
The first %s is replaced with %d, but doesn't hijack the '0'. If you
want to interpolate the %d, use the sentinel. The sentinel is what
causes '%%' to be handled.
"%sss%i" % "%d" % 0 % 1
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: not all arguments converted during string formatting
"%sss%i" % "%d" % 0 % str.interp_end % 1
'1ss0'
Treating tuples as a special case appears to be the simpler solution,
but this, 'chaining', to adopt the term, is still feasible.
A possible solution occurred to me shortly after I posted, but I decided
that sleep was more important. :-)
The original format is a string. The result of '%' is a string if
there's only 1 placeholder to fill, or a (partial) format object (class
"Format"?) if there's more than one. Similarly, the format object
supports '%'. The result of '%' is a string if there's only 1
placeholder to fill, or a new (partial) format object if there's more
than one.
>>> f = "%r %i"
>>> type(f)
<type 'str'>
>>> f = f % (2, 3, 4)
>>> type(f)
<type 'Format'>
>>> f = f % 1
>>> type(f)
<type 'str'>
Alright, so how are you handling:
f= "%s %i"
type( f )
<type 'str'>
f= f% '%i' #now '%i %i'
type( f )
<type 'Format'>
f= f% 1
type( f )
?
In other words, are you slipping '1' in to the very first available
slot, or the next, after the location of the prior?
Let's assume that Format objects display their value like the equivalent
string format:
>>> f = "%r %i"
>>> f
'%r %i'
>>> f = f % (2, 3, 4)
>>> f
<Format '(2, 3, 4) %i'>
>>> f = f % 1
>>> f
'(2, 3, 4) 1'
>>>
>>> f = "%s %i"
>>> f
'%s %i'
>>> f = f % '%i'
>>> f
<Format '%%i %i'>
>>> f = f % 1
>>> f
'%%i 1'
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