How can I sum a list of string objects in Python?

Question

I want to make a function that takes a list which contains some words and prints only the first letter of each word in order to make one new word.

So my function is right here:

def word(x):
    li = []
    for w in x:
        li.append(w[0])
    return sum(li)

But unfortunately, it gives me the following error:
TypeError: unsupported operand type(s) for +: 'int' and 'str'

Can you please explain me why is this happening ?

`sum` is for adding up numbers. If you want to join together a list of strings into one string, use `''.join(mylist)`. — khelwood, Dec 21 '17 at 13:34
The default starting value for `sum` is `0`, hence it is trying to add the first character to `0`. You should use `str.join`. — jonrsharpe, Dec 21 '17 at 13:34
I didn't know that use of .join method. Thank you for the fast responding ! — Kostas Petrakis, Dec 21 '17 at 13:36

score 2 · Answer 1 · answered Dec 21 '17 at 13:37

2

assuming words are separated by space,

S="this is my sentense"

"".join(map(lambda x: x[0], S.split(" ")))

returns

'tims'

explanation :

split in words using space
for each word ("map" function), take first character (x[0])
then join the result using void

answered Dec 21 '17 at 13:37

Setop

2,262
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28

2

or simply `"".join([x[0] for x in S.split(" ")])` – Ma0 Dec 21 '17 at 13:41
1

@Ev.Kounis No need for `[]`, `"".join(x[0] for x in S.split())` suffices here. – RoadRunner Dec 21 '17 at 13:43
@RoadRunner There are rumors that building the list is actually faster. I'll try to find a link for you. – Ma0 Dec 21 '17 at 13:44
Hmm please do, I'm curious about that. – RoadRunner Dec 21 '17 at 13:45
3

@RoadRunner Actually, `''join` is special, and [passing lists to it are actually faster than passing generators](https://stackoverflow.com/a/9061024/4909087). – cs95 Dec 21 '17 at 13:45
@cᴏʟᴅsᴘᴇᴇᴅ Wow, I didn't know that. I guess I learnt something new today. – RoadRunner Dec 21 '17 at 13:47

How can I sum a list of string objects in Python?

1 Answers1