TypeError: 'float' object does not support item assignment

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

The Python "TypeError: 'float' object does not support item assignment" occurs when we try to assign a value to a float using square brackets. To solve the error, correct the assignment or the accessor, as we can't mutate a floating-point number.

Here is an example of how the error occurs.

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my_float = 1.1

# ⛔️ TypeError: 'float' object does not support item assignment
my_float[0] = 5

We tried to access the float at index 0 and change the digit which caused the error.

If you mean to declare another floating-point number, simply declare a separate variable with a different name.

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my_float = 1.1

my_other_float = 2.2

Primitives like floats, integers and strings are immutable in Python, so chances are you meant to change a float value in a list.

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my_list = [1.1, 2.2]

my_list[0] = 9.9
print(my_list)  # 👉️ [9.9, 2.2]

my_list.append(3.3)
print(my_list)  # 👉️ [9.9, 2.2, 3.3]

my_list.insert(0, 10.1)
print(my_list)  # 👉️ [10.1, 9.9, 2.2, 3.3]

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

If you have two-dimensional lists, you have to access the list item at the correct index when updating it.

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my_list = [[1.1], [2.2], [3.3]]

my_list[0][0] = 9.9

print(my_list)

We accessed the first nested list (index 0) and then updated the value of the first item in the nested list.

If you need to get a new list by running a computation on each float value of the original list, use a list comprehension.

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my_list = [1.1, 2.2, 3.3]

my_new_list = [x + 1.5 for x in my_list]

print(my_new_list)  # 👉️ [2.6, 3.7, 4.8]

The Python "TypeError: 'float' object does not support item assignment" is caused when we try to mutate the value of a float.

If you aren't sure what type a variable stores, use the built-in type() class.

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my_float = 3.3
print(type(my_float))  # 👉️ <class 'float'>
print(isinstance(my_float, float))  # 👉️ True

The type class returns the type of an object.

The isinstance function returns True if the passed in object is an instance or a subclass of the passed in class.

Conclusion #

The Python "TypeError: 'float' object does not support item assignment" occurs when we try to assign a value to a float using square brackets. To solve the error, correct the assignment or the accessor, as we can't mutate a floating-point number.