python nested list comprehension string concatenation

Question

I have a list of lists in python looking like this:

[['a', 'b'], ['c', 'd']]

I want to come up with a string like this:

a,b;c,d

So the lists should be separated with a ; and the values of the same list should be separated with a ,

So far I tried ','.join([y for x in test for y in x]) which returns a,b,c,d. Not quite there, yet, as you can see.

"So the lists should be separated with a ; and the values of the same list should be separated with a ," - that's not a python list then. It's a string — matcheek
– matcheek, Commented Jun 17, 2015 at 9:07
yes, the final output should be a string. will update the question accordingly to make that clear. — beta
– beta, Commented Jun 17, 2015 at 9:08

NeoWang · Accepted Answer · 2015-06-17 09:07:52Z

9

";".join([','.join(x) for x in a])

answered Jun 17, 2015 at 9:07

NeoWang

18.8k24 gold badges87 silver badges134 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

my actual data contains float values :/ and python now errors TypeError: sequence item 0: expected str instance, float found...

okay in that case i need to use this code: ";".join([','.join(map(str, x)) for x in value])

Dan D. · Accepted Answer · 2015-06-17 09:08:28Z

7

>>> ';'.join(','.join(x) for x in [['a', 'b'], ['c', 'd']])
'a,b;c,d'

answered Jun 17, 2015 at 9:08

Dan D.

75k15 gold badges111 silver badges129 bronze badges

Padraic Cunningham · Accepted Answer · 2015-06-17 10:18:59Z

1

To do it functionally you could use map:

l = [['a', 'b'], ['c', 'd']]


print(";".join(map(".".join, l)))
a.b;c.d

answered Jun 17, 2015 at 10:18

181k30 gold badges264 silver badges327 bronze badges