Python list of integers to comma separated string

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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Convert list of integers to comma-separated string in Python #

To convert a list of integers to a comma-separated string:

1. Use a generator expression to iterate over the list.
2. Use the str() class to convert each integer to a string.
3. Use the str.join() method to join the values into a string with a comma separator.

Copied!
list_of_integers = [1, 3, 5, 7]

my_str = ','.join(str(item) for item in list_of_integers)

print(my_str)  # 👉️ 1,3,5,7

The str.join method takes an iterable as an argument and returns a string which is the concatenation of the strings in the iterable.

Note that the method raises a TypeError if there are any non-string values in the iterable.

If your list contains numbers or other types, you have to convert all of the values to strings before calling join().

We used a generator expression to iterate over the list and used the str() class to convert each integer to a string.

Copied!
list_of_integers = [1, 3, 5, 7]

my_str = ','.join(str(item) for item in list_of_integers)

print(my_str)  # 👉️ 1,3,5,7

Generator expressions are used to perform some operation for every element or select a subset of elements that meet a condition.

The string the join() method is called on is used as the separator between the elements.

If you don't need a separator and just want to join the list's elements into a string, call the join() method on an empty string.

Copied!
list_of_integers = [1, 3, 5, 7]

my_str = ''.join(str(item) for item in list_of_integers)

print(my_str)  # 👉️ '1357'

If you need to convert the list of integers to a space-separated string, call the join() method on a string containing a space.

Copied!
list_of_integers = [1, 3, 5, 7]

my_str = ' '.join(str(item) for item in list_of_integers)

print(my_str)  # 👉️ 1 3 5 7

Alternatively, you can use the map() function to convert the values in the list to strings before calling join().

Copied!
list_of_integers = [1, 3, 5, 7]

my_str = ' '.join(map(str, list_of_integers))

print(my_str)  # 👉️ 1 3 5 7

The map() function takes a function and an iterable as arguments and calls the function with each item of the iterable.

The str() class gets called with each number in the list and converts the values to strings.

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