I'm new to python, and have a list of longs which I want to join together into a comma separated string.
In PHP I'd do something like this:
$output = implode[",", $array]
In Python, I'm not sure how to do this. I've tried using join, but this doesn't work since the elements are the wrong type [i.e., not strings]. Do I need to create a copy of the list and convert each element in the copy from a long into a string? Or is there a simpler way to do it?
asked Jan 13, 2009 at 11:24
3
You have to convert the ints to strings and then you can join them:
','.join[[str[i] for i in list_of_ints]]
answered Jan 13, 2009 at 11:28
4
You can use map to transform a list, then join them up.
",".join[ map[ str, list_of_things ] ]
BTW, this works for any objects [not just longs].
answered Jan 13, 2009 at 11:30
S.LottS.Lott
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2
You can omit the square brackets from heikogerlach's answer since Python 2.5, I think:
','.join[str[i] for i in list_of_ints]
This is extremely similar, but instead of building a [potentially large] temporary list of all the strings, it will generate them one at a time, as needed by the join function.
2
and yet another version more [pretty cool, eh?]
str[list_of_numbers][1:-1]
answered Jul 22, 2009 at 7:36
fortranfortran
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0
Just for the sake of it, you can also use string formatting:
",".join["{0}".format[i] for i in list_of_things]
Hubert Kario
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answered Jan 13, 2009 at 11:46
Tom DunhamTom Dunham
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Not the answer you're looking for? Browse other questions tagged python or ask your own question.
Created: January-03, 2022
- Use the
join[]Function to Convert a List to a Comma-Separated String in Python - Use
the
StringIOModule to Convert a List to a Comma-Separated String in Python
We can use a list to store different elements under a common name. A string is a collection of characters.
We will convert a list to a comma-separated string in this tutorial.
Use the join[] Function to Convert a List to a Comma-Separated String in Python
The join[] function combines the elements of
an iterable and returns a string. We need to specify the character that will be used as the separator for the elements in the string.
To create a comma-separated string, we will use the comma as the separator.
See the code below.
lst = ['c','e','a','q']
s = ",".join[lst]
print[s]
Output:
c,e,a,q
The above method is only limited to a list containing strings.
We can use list comprehension and the str[] function to work with a list containing integers or other elements. With list comprehension, we can iterate
over the elements easily in a single line using the for loop, and convert each element to a string using the str[] function.
We implement this in the following code.
lst = [8,9,4,1]
s = ",".join[[str[i] for i in lst]]
print[s]
Output:
8,9,4,1
We can also eliminate list comprehension by using the map[] function. The map[] function can be used to convert all elements of the list to a string by
applying the str[] function to every element.
For example,
lst = [8,9,4,1]
s = ",".join[map[str,lst]]
print[s]
Output:
8,9,4,1
Use the StringIO Module to Convert a List to a Comma-Separated String in Python
The StringIO object is similar to a file object but in memory to work with texts. In Python 2, it can be imported directly using the StringIO module. In Python 3, it was stored in the io module.
We can use the
csv.writerow[] function to write the list as a comma-separated row for a CSV file in the StringIO object. For this, we need to instantiate a csv.writer object first. We can then store the contents of this object in a string using the getvalue[] function.
See the following code.
import io
import csv
lst = [8,9,4,1]
s_io = io.StringIO[]
writer = csv.writer[s_io]
writer.writerow[lst]
s = s_io.getvalue[]
print[s]
Output:
8,9,4,1
We can also use the print[] function with the unpack operator. The unpack operator * unpacks all the elements of an iterable, and stores it in the StringIO object
using the file parameter in the print[] function.
See the code below.
import io
lst = [8,9,4,1]
s_io = io.StringIO[]
print[*lst, file=s_io, sep=',', end='']
s = s_io.getvalue[]
print[s]
Output:
8,9,4,1
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