AttributeError: 'list' object has no attribute 'upper'

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Borislav Hadzhiev

Wed Apr 20 20222 min read

AttributeError: 'list' object has no attribute 'upper' #

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.

attributeerror list object has no attribute upper

Here is an example of how the error occurs.

main.py
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.

The 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().

main.py
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.

main.py
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.

main.py
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.

The "AttributeError: 'list' object has no attribute 'upper'" occurs when we try to call the 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.

main.py
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.

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