Antoine Pitrou wrote:
Michael Foord <fuzzyman <at> voidspace.org.uk> writes:
Simple string formatting with %s and a single object or a tuple meets
>90% of my string formatting needs.
Not to mention that e.g. "%r" % s is much simpler than "{0!r}".format(s)
(if I got the format spec right).
repr(s) is even simpler :)
The basic idea for conversions to the new formatting:
'%r' % v --> repr(v) # or ascii(v) if more appropriate
'%s' % v --> str(v) # or format(v), or format(v, '')
The str/unicode stability that the latter provided in 2.x is no longer
needed in 3.x. The first one never had any advantage that I can see over
invoking repr() directly (since repr() and %r always produce an 8-bit
string in 2.x)
The conversion of fmt % v depends on both fmt and v:
v is a single value, fmt is only a formatting code:
'%x' % v--> format(v, 'x')
v is a single value, fmt is both a formatting code and additional text:
'Value: %x' % v--> 'Value: {0:x}'.format(v)
Note that the old code in this case wouldn't display dict or tuple
instances correctly. Avoiding that ambiguity is a major advantage of the
new approach.
v is a tuple* (more on this below):
'Key: %s Value: %s' % k, v --> 'Key: {0} Value: {1}'.format(k, v)
fmt uses named parameters:
'Value: %(val)s' % dict(val=v) --> 'Value: {val}'.format(val=v)
* I still think the new str.format approach is too verbose and requires
too much thought for simple use cases where the printf-style %
replacement hits a sweet spot between being easy to write and easy to read.
So I see the introduction of str.format in 3.0 as an opportunity to
*fix* %-formatting later in the 3.x series rather than get rid of it
entirely. The fixes I would apply:
- remove support for %(name)s based formatting (str.format is vastly
superior once you start naming the parameters).
- remove support for passing a single value to a format string without
wrapping it in an iterable first
- accept any iterable as the right hand argument str.__mod__
This approach would eliminate the current ambiguity in fmt.v, and would
allow fmt % [x] to be used to box an argument for safe use in a
single-parameter format string instead of having to muck around with
singleton tuples.
Cheers,
Nick.
--
Nick Coghlan | [EMAIL PROTECTED] | Brisbane, Australia
---------------------------------------------------------------
http://www.boredomandlaziness.org
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