Borislav Hadzhiev
Wed Apr 20 2022·2 min read
Photo by Spencer Watson
The Python "AttributeError: 'list' object has no attribute 'upper'" occurs
when we call the upper()
method on a list instead of a string. To solve the
error, call upper()
on a string, e.g. by accessing the list at a specific
index or by iterating over the list.
Here is an example of how the error occurs.
my_list = ['hello', 'world'] # ⛔️ AttributeError: 'list' object has no attribute 'upper' my_list.upper()
We created a list with 2 elements and tried to call the upper()
method on the
list which caused the error.
upper()
method is string-specific, so we have to call it on a string, and not on a list object.One way to solve the error is to access the list at a specific index before
calling upper()
.
my_list = ['hello', 'world'] result = my_list[0].upper() print(result) # 👉️ "HELLO"
We accessed the list element at index 0
and called the upper()
method on the
string.
If you need to call the upper()
method on each string in a list, use a list
comprehension.
my_list = ['hello', 'world'] new_list = [word.upper() for word in my_list] print(new_list) # 👉️ ['HELLO', 'WORLD']
Alternatively you can use a for
loop to call the upper
method on each string
in the list.
my_list = ['hello', 'world'] for word in my_list: result = word.upper() print(result) # 👉️ "HELLO", "WORLD"
We used a for
loop to iterate over the list and called the upper()
method on
each string.
The str.upper method returns a copy of the string with all the cased characters converted to uppercase.
The method does not change the original string, it returns a new string. Strings are immutable in Python.
upper()
method on a list instead of a string.To solve the error, you either have to correct the assignment of the variable
and make sure to call upper()
on a string, or call upper()
on an element in
the list that is of type string
.
You can either access the list at a specific index, e.g. my_list[0]
or use a
for loop to iterate over the list if you have to call upper()
on each element.
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 upper()
is not a method implemented by lists, the error is caused.