Python - convert list of tuples to string

Question

Which is the most pythonic way to convert a list of tuples to string?

I have:

[(1,2), (3,4)]

and I want:

"(1,2), (3,4)"

My solution to this has been:

l=[(1,2),(3,4)]
s=""
for t in l:
    s += "(%s,%s)," % t
s = s[:-1]

Is there a more pythonic way to do this?

What are these tuples for, why do they need to be in a string, and do they in fact need to be tuples? — Ignacio Vazquez-Abrams, Jul 20 '10 at 17:31
@Ignacio, @SilentGhost: I'd love to have you guys elaborate more on your comments (I'm still learning Python myself). It may not be an actual answer to OP's string formatting problem, but I'm sure you guys have very important points to make. — polygenelubricants, Jul 20 '10 at 19:34
@polygenelubricants: Bottom line: there's no point to this. The tuple -- as a tuple -- is a fine structure. Why mess with it to make an obscurely formatted string? If all they want is a string, then the `string.format` method will do the job pretty simply. If they want something else, then the question should say what they're tying to accomplish. — S.Lott, Jul 20 '10 at 20:22
@Ignacio Vazquez-Abrams, @SilentGhost: This string is the last part of a SQL query string: 'INSERT INTO table (field1, field) VALUES %s' % s. I know there are good frameworks out there like SQLAlchmey or Django, to do this kind of things, but I don't want to use it in this case. — ssoler, Jul 21 '10 at 07:59
Wait, what? You **want** to introduce SQL injection attacks into your code? Python gives you the tools to do it right and you want to go **out of your way to do it wrong?** I have no words. — Ignacio Vazquez-Abrams, Jul 21 '10 at 08:11
@Ignacio Vazquez-Abrams: Thanks for the advice. I'm aware of this. It's just a quick and dirty script to move some data. — ssoler, Jul 21 '10 at 13:07
Does anyone have a link for the question that does the exact opposite (i.e., string to tuple)? — cs95, Jul 06 '20 at 08:28

polygenelubricants · Answer 1 · 2010-07-20T17:49:11.580

38

You can try something like this (see also on ideone.com):

myList = [(1,2),(3,4)]
print ",".join("(%s,%s)" % tup for tup in myList)
# (1,2),(3,4)

edited Jul 20 '10 at 17:49

answered Jul 20 '10 at 17:30

polygenelubricants

376,812
128
561
623

while @mykhal's solution is simpler, I think this is prettier :) – Ritwik Bose Jan 09 '13 at 17:10
Pythonic, robust and short. Thanks. – Neowizard Nov 12 '17 at 16:26

mykhal · Accepted Answer · 2014-07-23T13:12:12.877

37

you might want to use something such simple as:

>>> l = [(1,2), (3,4)]
>>> str(l).strip('[]')
'(1, 2), (3, 4)'

.. which is handy, but not guaranteed to work correctly

edited Jul 23 '14 at 13:12

answered Jul 20 '10 at 17:34

mykhal

19,175
11
72
80

3

What if the tuples are tuples of strings which contain []? – Rob Lourens Jul 20 '10 at 17:42
6

@Rob: `str.strip()` only removes from the ends. – Ignacio Vazquez-Abrams Jul 20 '10 at 17:44
6

It seems like bad practice to rely on the internal string representation of a list. – Stephen Niedzielski Apr 29 '13 at 19:55
1

@mykhal it cause some problem with unicode caracters – GeoStoneMarten Mar 20 '17 at 14:14
Not going to work either if you want to join with a different separator. – Yohan Obadia Jul 13 '17 at 08:52

score 21 · Answer 3 · answered Jul 20 '10 at 19:13

21

How about:

>>> tups = [(1, 2), (3, 4)]
>>> ', '.join(map(str, tups))
'(1, 2), (3, 4)'

answered Jul 20 '10 at 19:13

pillmuncher

10,094
2
35
33

1

Cleanest solution by far ! – Yohan Obadia Jul 13 '17 at 08:51
most "pythonic" answer. – shahar_m Oct 16 '17 at 08:27

score 2 · Answer 4 · answered Jun 06 '18 at 18:29

2

The most pythonic solution is

tuples = [(1, 2), (3, 4)]

tuple_strings = ['(%s, %s)' % tuple for tuple in tuples]

result = ', '.join(tuple_strings)

answered Jun 06 '18 at 18:29

ValarDohaeris

6,064
5
31
43

score 1 · Answer 5 · edited Jul 03 '12 at 07:50

1

I think this is pretty neat:

>>> l = [(1,2), (3,4)]
>>> "".join(str(l)).strip('[]')
'(1,2), (3,4)'

Try it, it worked like a charm for me.

edited Jul 03 '12 at 07:50

Maehler

6,111
1
41
46

answered Jul 03 '12 at 07:10

luissanchez

11
1

score 1 · Answer 6 · answered Jul 20 '10 at 17:44

1

How about

l = [(1, 2), (3, 4)]
print repr(l)[1:-1]
# (1, 2), (3, 4)

answered Jul 20 '10 at 17:44

Benj

1,853
4
18
27

The spacing here isn't actually as you stipulated; if that's important, this approach won't work as python adds a space after each item in a list/tuple. – Benj Jul 20 '10 at 17:47

score 0 · Answer 7 · answered Aug 19 '10 at 20:49

0

Three more :)

l = [(1,2), (3,4)]

unicode(l)[1:-1]
# u'(1, 2), (3, 4)'

("%s, "*len(l) % tuple(l))[:-2]
# '(1, 2), (3, 4)'

", ".join(["%s"]*len(l)) % tuple(l)
# '(1, 2), (3, 4)'

answered Aug 19 '10 at 20:49

blaztinn

343
4
8

Python - convert list of tuples to string

7 Answers7

Linked