convert list to string in python

Question

TypeError: can only join an iterable

I'm trying to convert a list of integers to string. And it shows me the above error. What am I doing wrong?

Expected output: 10,5,78

l=[10,5,78]
s=''
for i in l:
    s=s.join(i)
print(s)

As the error message says, `s.join` "can only join an iterable". Is the `i` an iterable? No, it's an integer, and integers cannot be iterated over. You can just do `s = str(l)[1:-1]`, for example — ForceBru, Jan 04 '20 at 14:18
@ForceBru That worked like magic. Can you please explain what [1:-1] does? — Vishal Pallikonda, Jan 04 '20 at 14:24
@VishalPallikonda, it converts `l` to the string `"[10, 5, 78]"` and returns its characters except the first (`1`) and the last (`-1`) ones (the brackets). The `[1:-1]` syntax is called _slicing_ — ForceBru, Jan 04 '20 at 14:26
@ForceBru this solution gives extra space after comma and so doesn’t fit the expected output and it also doesn’t help VishalPallikonda learn the join syntax. — Tim, Jan 04 '20 at 14:29
You just need `s = ''.join(str(_) for _ in l)` or `s = ','.join(str(_) for _ in l)`, if you want the numbers comma separated. — accdias, Jan 04 '20 at 14:30
@Tim, the output is very close, though (I'm 90% sure the spaces don't matter that much here), and it's simple to make it match the desired output exactly: `str(l)[1:-1].replace(' ', '')` — ForceBru, Jan 04 '20 at 14:34
@ForceBru It’s an interesting and imaginative solution. There is no doubt :) But I think for beginners it’s better to master the basics before trying something fancy like this ;) — Tim, Jan 04 '20 at 14:43

score 5 · Accepted Answer · edited Feb 04 '20 at 20:18

5

Join doesn’t work the way you think it works.

What join does:

",".join(["a", "b", "c"])

Gives "a,b,c". Essentially it creates a string by elements from a list with what you provided before .join, in this case it’s a comma.

So what you want can be achieved by

",".join(str(x) for x in l)

The inside expression changes the integers in list l into strings before joining them by comma.

edited Feb 04 '20 at 20:18

Hollay-Horváth Zsombor

604
6
15

answered Jan 04 '20 at 14:25

Tim

3,178
1
13
26

score 2 · Answer 2 · answered Jan 04 '20 at 15:47

.join() method acts on an existing string and accepts a list of strings. Join every item of the given list separated by the string acting on.

>>> l = [10, 5, 78]
>>> l = [str(i) for i in l]    # map to a list of strings
>>> s = ','.join(l)            # join all the strings separated by a comma
>>> s
'10,5,78'

convert list to string in python

2 Answers2

Linked