How to concatenate items in a list to a single string?

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How to concatenate items in a list to a single string?

Is there a simpler way to concatenate string items in a list into a single string? Can I use the str.join() function?

E.g. this is the input ['this','is','a','sentence'] and this is the desired output this-is-a-sentence

sentence = ['this','is','a','sentence']
sent_str = ""
for i in sentence:
    sent_str += str(i) + "-"
sent_str = sent_str[:-1]
print sent_str
Asked By: alvas


Answer #1:

Use join:

>>> sentence = ['this', 'is', 'a', 'sentence']
>>> '-'.join(sentence)
>>> ' '.join(sentence)
'this is a sentence'
Answered By: Burhan Khalid

Answer #2:

A more generic way to convert python lists to strings would be:

>>> my_lst = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
>>> my_lst_str = ''.join(map(str, my_lst))
>>> print(my_lst_str)
Answered By: Aaron S

Answer #3:

It’s very useful for beginners to know
why join is a string method.

It’s very strange at the beginning, but very useful after this.

The result of join is always a string, but the object to be joined can be of many types (generators, list, tuples, etc).

.join is faster because it allocates memory only once. Better than classical concatenation (see, extended explanation).

Once you learn it, it’s very comfortable and you can do tricks like this to add parentheses.

>>> ",".join("12345").join(("(",")"))
>>> list = ["(",")"]
>>> ",".join("12345").join(list)
Answered By: Wallebot

Answer #4:

Edit from the future: Please don’t use this, this function was removed in Python 3 and Python 2 is dead. Even if you are still using Python 2 you should write Python 3 ready code to make the inevitable upgrade easier.

Although @Burhan Khalid’s answer is good, I think it’s more understandable like this:

from str import join
sentence = ['this','is','a','sentence']
join(sentence, "-")

The second argument to join() is optional and defaults to ” “.

Answered By: SilentVoid

Answer #5:

We can specify how we have to join the string. Instead of ‘-‘, we can use ‘ ‘

sentence = ['this','is','a','sentence']
s=(" ".join(sentence))
Answered By: Abhishek V

Answer #6:

We can also use Python’s reduce function:

from functools import reduce
sentence = ['this','is','a','sentence']
out_str = str(reduce(lambda x,y: x+"-"+y, sentence))
Answered By: Nishkarsh Dixit

Answer #7:

list = ['aaa', 'bbb', 'ccc']
string = ''.join(list)
>>> aaabbbccc
string = ','.join(list)
>>> aaa,bbb,ccc
string = '-'.join(list)
>>> aaa-bbb-ccc
string = 'n'.join(list)
>>> aaa
>>> bbb
>>> ccc
Answered By: mounirboulwafa

Answer #8:

This will help for sure –

arr=['a','b','h','i']     # let this be the list
s=""                      # creating a empty string
for i in arr:
   s+=i                   # to form string without using any function
Answered By: Abhishek Chauhan

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