Borislav Hadzhiev
Wed Apr 20 2022·2 min read
Photo by Ivana Cajina
The Python "AttributeError: 'list' object has no attribute 'join'" occurs when
we call the join()
method on a list object. To solve the error, call the
join
method on the string separator and pass the list as an argument to
join
, e.g. '-'.join(['a','b'])
.
Here is an example of how the error occurs.
my_list = ['a', 'b', 'c'] # ⛔️ AttributeError: 'list' object has no attribute 'join' my_str = my_list.join('-')
We tried to call the join()
method on the list which caused the error.
To solve the error, call the join()
method on the string separator and pass it
the list as an argument.
my_list = ['a', 'b', 'c'] my_str = '-'.join(my_list) print(my_str) # 👉️ "a-b-c"
The str.join method takes an iterable as an argument and returns a string which is the concatenation of the strings in the iterable.
The string the method is called on is used as the separator between elements.
If you don't need a separator and just want to join the list elements into a
string, call the join()
method on an empty string.
my_list = ['a', 'b', 'c'] my_str = ''.join(my_list) print(my_str) # 👉️ "abc"
Note that the join()
method raises a TypeError
if there are any non-string
values in the iterable.
If your list contains numbers, or other types, convert all of the values to
string before calling join()
.
my_list = ['a', 'b', 1, 2] all_strings = list(map(str, my_list)) print(all_strings) # 👉️ ['a', 'b', '1', '2'] result = ''.join(all_strings) print(result) # 👉️ "ab12"
join()
method on a list instead of a string.To solve the error, you have to call the method on a string, and pass the list
as an argument to join()
.
You can view all the attributes an object has by using the dir()
function.
my_list = ['a', 'b', 'c'] # 👉️ [... 'append', 'clear', 'copy', 'count', 'extend', 'index', # 'insert', 'pop', 'remove', 'reverse', 'sort' ...] print(dir(my_list))
If you pass a class to the dir() function, it returns a list of names of the classes' attributes, and recursively of the attributes of its bases.
If you try to access any attribute that is not in this list, you would get the "AttributeError: list object has no attribute" error.
Since join()
is not a method implemented by lists, the error is caused.