TypeError: 'set' object does not support item assignment

TypeError: 'set' object does not support item assignment #

The Python "TypeError: 'set' object does not support item assignment" occurs when we try to change the value of a specific item in a set. If you meant to declare a list, use square brackets instead of curly braces, e.g. my_list = [].

Here is an example of how the error occurs.

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my_set = {'a', 'b', 'c'}

# ⛔️ TypeError: 'set' object does not support item assignment
my_set[0] = 'z'

Set objects are an unordered collection of unique elements, so they don't support indexing and slicing.

If you meant to declare a list, use square brackets instead of curly braces.

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my_list = ['a', 'b', 'c']

# 👇️ update the value of an item at specific index
my_list[0] = 'z'

print(my_list)  # 👉️ ['z', 'b', 'c']

# 👇️ add item to the end of the list
my_list.append('d')
print(my_list)  # 👉️ ['z', 'b', 'c', 'd']

# 👇️ insert item at specific index
my_list.insert(0, '.')
print(my_list) # 👉️ ['.', 'z', 'b', 'c', 'd']

We changed the value of the list element at index 0.

Lists are an ordered collection of items, so accessing the list at a specific index makes sense.

On the other hand, set objects are unordered collections of unique elements, so they don't have indices.

If you meant to add an item to a set, use the add() method.

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my_set = {'a', 'b', 'c'}

my_set.add('d')

print(my_set) # 👉️ {'d', 'c', 'b', 'a'}

The set.add method adds the provided element to the set.

You can pass a set object to the list() constructor to convert a set to a list, but since set objects are unordered, running the same code multiple times would produce a list containing the same elements in different order.

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my_set = {'a', 'b', 'c'}

my_list = list(my_set)

print(my_list)  # 👉️ ['a', 'c', 'b']
print(my_list[0])  # 👉️ 'a'

If you meant to declare a dictionary, containing key-value pairs, use the following syntax.

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my_dict = {'name': 'Alice', 'age': 30}

print(my_dict['name'])  # 👉️ "Alice"
print(my_dict['age'])  # 👉️ 30

Notice that we separate the keys and values with a colon when declaring a dictionary.