Python 3 - using tuples in str.format() [duplicate]

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What is the pythonic way to unpack tuples? [duplicate] (2 answers)

I'm trying to use the str.format() method, and having some difficulties when my values are stored within a tuple. For example, if I do:

s = "x{}y{}z{}"
s.format(1,2,3)

Then I get 'x1y2z3' - no problem.
However, when I try:

s = "x{}y{}z{}"
tup = (1,2,3)
s.format(tup)

I get

IndexError: tuple index out of range.

So how can I 'convert' the tuple into separate variables? or any other workaround ideas?

Answer 1

Pass in the tuple using *arg variable arguments call syntax:

s = "x{}y{}z{}"
tup = (1,2,3)
s.format(*tup)

The * before tup tells Python to unpack the tuple into separate arguments, as if you called s.format(tup[0], tup[1], tup[2]) instead.

Or you can index the first positional argument:

s = "x{0[0]}y{0[1]}z{0[2]}"
tup = (1,2,3)
s.format(tup)

Demo:

>>> tup = (1,2,3)
>>> s = "x{}y{}z{}"
>>> s.format(*tup)
'x1y2z3'
>>> s = "x{0[0]}y{0[1]}z{0[2]}"
>>> s.format(tup)
'x1y2z3'

Answer 2

You can unpack the contants of the tuple.

s=s.format(*t)