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

Question

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?

You are actually passing a single argument that is a tuple. — Vishnu Upadhyay
– Vishnu Upadhyay, Commented Nov 5, 2014 at 13:26
def fun(*args): print('My args: {!a}'.format(args)) I just don't know yet what 'a' means, but it seems to be a 'conversion specifier'. I've also seen the use of 'r'. — eltbus
– eltbus, Commented Oct 20, 2019 at 16:17

Community · Accepted Answer · 2017-05-23 12:01:48Z

32

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'

edited May 23, 2017 at 12:01

CommunityBot

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answered Nov 5, 2014 at 13:25

Martijn Pieters

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3 Comments

soungalo Over a year ago

Thanks! it worked, but can you explain more what's actually going on with the *? or refer me to the right place in the documentation?

Martijn Pieters Over a year ago

@soungalo: see What does ** (double star) and * (star) do for Python parameters?

Tim Over a year ago

This really helpful if used inside map() and you don't want to define lambda or custom function to use * to unpack the tuple! This is the only solution (that I could find) that talks about indexing in format to unpack tuple. Cheers!

user93 · Accepted Answer · 2014-11-05 13:30:41Z

-3

You can unpack the contants of the tuple.

s=s.format(*t)

answered Nov 5, 2014 at 13:30

user93

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3 Comments

Kevin Over a year ago

This doesn't seem to add anything not already covered in an existing answer.

ArtOfWarfare Over a year ago

@Kevin - So downvote it. Don't flag it.

Sean Over a year ago

shorter is better

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