On 06/21/2011 05:19 PM, Terry Reedy wrote:
On 6/21/2011 7:33 AM, Tim Chase wrote:
<URL:http://docs.python.org/library/stdtypes.html#str.format>
Is there a good link to a thread-archive on when/why/how .format(...)
became "preferred to the % formatting"?
That is a controversial statement.
I'm not sure whether you're "controversial" refers to
- the documentation at that link,
I meant the preceding statement (derived from the linked source, but
that is not important) that .format is preferred to %.
I guess then with all the contention, having such a vocal
preference in the docs (even if tempered by "in new code") seems
to unnecessarily polarize when I find myself very "meh" in either
direction.
multi_warn = '''\
Warning: testing multiple {0}s against an iterator will only test
the first {0} unless the iterator is reiterable; most are not.'''.format
...
print(multiwarn('function'))
...
print(multiwarn('iterator'))
Does the gotcha of a non-restarting iterator
Huh? What iterator?
Your string-body text warns about behavior regarding iterators.
I was thrown by your warning.
The other new feature I saw was the use of __format__()
Suppose one had a Money class with currency and decimal amount fields.
.__str__ can add a currency symbol (before or after as appropriate) but
has to use a standard format for the amount field. .__float__ can be
post-processed according to a %...f spec, but cannot include a currency
symbol. Money.__format__(self,spec) can format the amount at it wishes,
including its rounding rules, *and* add a currency symbol.
A Money class was one of the first things I thought of, but
figured that would be better relegated to an i18n wrapper if you
wanted it. Such a wrapper would handle currency-symbol choice &
positioning positioning (before vs. after; relation to the +/-;
optional characters for thousands-separators and decimal
separators; and partitioning at thousands-or-other-multiples, etc).
Or suppose one has a multi-precision float. %80.40f will require an mpf
instance to appoximate itself as a float, possibly with error.
mpg.__format__ should be able to do better.
This case makes a better argument, showing me some new value
added by __format__().
-tkc
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