If I have a string like:
"{0} {1} {1}" % ("foo", "bar")
and I want:
"foo bar bar"
What do the replacement tokens have to be? (I know that my example above is incorrect; I'm just trying to express my goal.)
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3 Answers
"{0} {1} {1}".format("foo", "bar")
4 Comments
Nick Heiner
Interesting. Why does that work with
"str".format(args) but not "str" % args?
Ignacio Vazquez-Abrams
@Rosarch: Because the
{n} syntax only works for str.format(), not str.__mod__().
mouad
@Rosarch: i guess you have mixed the new way with the old way of formating because the old way don't use
{} as a place holders :), but using the .format() is the new way of formating strings take a look at the pep 3101 for more detail : python.org/dev/peps/pep-3101
Dorian Dore
Could you pass more than one value to
{0}? For example, if you have two instances of {0} in a string, but you want to pass two different strings for each one?"%(foo)s %(foo)s %(bar)s" % { "foo" : "foo", "bar":"bar"}
is another true but long answer. Just to show you another viewpoint about the issue ;)
1 Comment
Kyle Wild
+1 because I didn't know you could do this, and I prefer the readability
Python 3 has exactly that syntax, except the % operator is now the format method. str.format has also been added to Python 2.6+ to smooth the transition to Python 3. See format string syntax for more details.
>>> '{0} {1} {1}' % ('foo', 'bar')
'foo bar bar'
It cannot be done with a tuple in older versions of Python, though. You can get close by using mapping keys enclosed in parentheses. With mapping keys the format values must be passed in as a dict instead of a tuple.
>>> '%(0)s %(1)s %(1)s' % {'0': 'foo', '1': 'bar'}
'foo bar bar'
From the Python manual:
When the right argument is a dictionary (or other mapping type), then the formats in the string must include a parenthesised mapping key into that dictionary inserted immediately after the '%' character. The mapping key selects the value to be formatted from the mapping.
