New Python 3.0 string formatting - really necessary?
arnodel at googlemail.com
Mon Dec 22 23:36:15 CET 2008
Steven D'Aprano <steve at REMOVE-THIS-cybersource.com.au> writes:
> 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.
Well that's easy. I see 'r' didn't answer so I will: only accept tuples
on the right hand side of the %, so all arguments have to be put inside
>>> "%s" % 42
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for %: 'str' and 'int'
>>> "%s" % (42,)
Of course there would still be the possibility of uncaught bugs when
people forget to put the argument in a tuple if the argument itself is a
tuple of length 1.
>>> def foo(x):
... print "foo(%s)" % x
... # should be % (x,)
TypeError: unsupported operand type(s) for %: 'str' and 'str'
>>> # But if x is a tuple of length 1 the error is not reported
That's why .format() is a better option IMHO.
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