nonetype' object does not support item assignment in python

• About Jason Ross

TypeError: 'NoneType' object does not support item assignment

• software development

This is an error that turns up occasionally when you're developing code in Python. It started happening in some code I was working on recently, and all of the articles I found when I was looking for the cause said the same thing; that you're trying to assign something to a value that's None . Probably something with an index or key, like a list or dictionary.

This didn't seem to match what I saw in my system at the time, but after looking much more closely it was right, although not for obvious reasons.

I wrote some code to duplicate the error, below:

Running this gave the following output:

This is a much more modern Python interpreter than the one I was using when I first saw the error - the original was reporting the error on line 32:

That was even more confusing, because details was declared and defined here, and make_details() should have been returning a value.

So, it looked like the error reporting in the Python interpreter was, shall we say, vague. The exception was detected at line 32 (above), but it was actually generated somewhere further down the call stack, presumably inside the make_details() function.

Thankfully, the error reporting in Python has improved over time, and line 11 is where the error is detected, even though really it's a symptom, not the actual problem.

The real problem is line 10:

It might not be immediately obvious, but dict.update() in an in-place function, which changes result during the call. Because of this it returns None , which is the actual cause of the problem.

Changing this line to:

fixes the problem.

This problem was one where the answer on the internet was correct, but the cause was harder to find in the code. A simple mistake, where the result of a function that returns None was assigned to a variable, deleted a valid dictionary. This made the following assignment to an indexed value invalid, which is what the error described.

The original code reported the error as occurring in the wrong place, where it was first encountered instead of where it was thrown. If there's nothing else to learn from this, it's that older versions of Python's error detection weren't always great, and so you should always use the newest version you can. Trust me, it'll save you time by at least getting you closer to the source of the problems.

I'm Jason Ross, a software architect and full-stack developer based in Calgary, Alberta, Canada. This is my portfolio site for my professional activities and articles.

I design and build software systems. Systems that provide value to you and your customers as quickly as possible.

I use various methods to automate every part of the process from development and building to deployment and integration testing.

I have an engineering background and I'm a  Chartered Engineer but I now design and write software mostly in C#, Python and C++ on both Windows and Linux, usually with SQL databases, although I've also developed with a few other languages.

If you need any help with your current project, or with a new one, please feel free to contact me.

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TypeError: Type object does not support item assignment: How to fix it?

TypeError: Type object does not support item assignment

Have you ever tried to assign a value to a property of a type object and received a TypeError? If so, you’re not alone. This error is a common one, and it can be frustrating to figure out what went wrong.

In this article, we’ll take a look at what a type object is, why you can’t assign values to its properties, and how to avoid this error. We’ll also provide some examples of how to work with type objects correctly.

So, if you’re ready to learn more about TypeErrors and type objects, read on!

What is a type object?

A type object is a special kind of object that represents a data type. For example, the `int` type object represents the integer data type, and the `str` type object represents the string data type.

Type objects are created when you use the `type()` function. For example, the following code creates a type object for the integer data type:

python int_type = type(1)

Type objects have a number of properties that you can use to get information about them. For example, the `__name__` property returns the name of the type, and the `__bases__` property returns a list of the type’s base classes.

Why can’t you assign values to type objects?

Type objects are immutable, which means that their values cannot be changed. This is because type objects are used to represent the abstract concept of a data type, and their values are not meant to be changed.

If you try to assign a value to a property of a type object, you’ll receive a TypeError. For example, the following code will raise a TypeError:

python int_type.name = “New name”

How to avoid TypeErrors

To avoid TypeErrors, you should never try to assign values to properties of type objects. If you need to change the value of a property, you should create a new object with the desired value.

For example, the following code correctly changes the value of the `name` property of an integer object:

python new_int = int(1) new_int.name = “New name”

TypeErrors can be frustrating, but they can usually be avoided by understanding what type objects are and how they work. By following the tips in this article, you can avoid these errors and write more robust code.

| Header 1 | Header 2 | Header 3 | |—|—|—| | TypeError: type object does not support item assignment | Definition | Cause | | An error that occurs when you try to assign a value to an element of a type object that does not support item assignment. | The type object is immutable, which means that its values cannot be changed. | Trying to assign a value to an element of a type object will result in a TypeError. |

A TypeError is a type of error that occurs when an operation or function is applied to an object of an inappropriate type. For example, trying to assign a value to an attribute of a type object will result in a TypeError.

TypeErrors can be difficult to debug, because they can occur in a variety of situations. However, by understanding what causes a TypeError, you can be better equipped to avoid them.

What causes a TypeError?

There are a few different things that can cause a TypeError:

• Using an incompatible data type: One of the most common causes of a TypeError is using an incompatible data type. For example, trying to add a string to a number will result in a TypeError.
• Using an invalid operator: Another common cause of a TypeError is using an invalid operator. For example, trying to divide a number by zero will result in a TypeError.
• Calling a method on an object that doesn’t support it: Finally, trying to call a method on an object that doesn’t support it can also result in a TypeError. For example, trying to call the `.sort()` method on a string will result in a TypeError.

There are a few things you can do to avoid TypeErrors:

• Be careful about the data types you use: Make sure that you are using the correct data types for your operations. For example, if you are adding two numbers, make sure that both numbers are numbers.
• Use the correct operators: Make sure that you are using the correct operators for your operations. For example, if you are dividing two numbers, use the `/` operator.
• Read the documentation: If you are not sure whether a method is supported by an object, read the documentation to find out.

By following these tips, you can help to avoid TypeErrors in your code.

TypeErrors can be a frustrating experience, but they can also be a learning opportunity. By understanding what causes a TypeError, you can be better equipped to avoid them. And by following the tips in this article, you can help to reduce the number of TypeErrors in your code.

Additional resources

• [Python TypeError documentation](https://docs.python.org/3/library/exceptions.htmlTypeError)
• [Stack Overflow: TypeError questions](https://stackoverflow.com/questions/tagged/typeerror)
• [Real Python: How to avoid TypeErrors in Python](https://realpython.com/python-typeerror/)

3. How to fix a TypeError?

To fix a TypeError, you need to identify the cause of the error and then take steps to correct it. Some common fixes include:

Using the correct data type

Using the correct operator

Calling the correct method on the object

Let’s take a look at some examples of how to fix each of these types of errors.

One of the most common causes of TypeErrors is using the wrong data type. For example, if you try to add a string to an integer, you will get a TypeError because strings and integers are different data types. To fix this error, you need to convert the string to an integer or the integer to a string.

x = ‘123’ y = 456

This will raise a TypeError because you cannot add a string to an integer z = x + y

To fix this error, you can convert the string to an integer z = int(x) + y

Another common cause of TypeErrors is using the wrong operator. For example, if you try to divide an integer by a string, you will get a TypeError because you cannot divide an integer by a string. To fix this error, you need to use the correct operator.

x = 123 y = ‘456’

This will raise a TypeError because you cannot divide an integer by a string z = x / y

To fix this error, you can use the `str()` function to convert the string to an integer z = x / int(y)

Finally, another common cause of TypeErrors is calling the wrong method on an object. For example, if you try to call the `len()` method on a string, you will get a TypeError because the `len()` method is not defined for strings. To fix this error, you need to call the correct method on the object.

x = ‘hello’

This will raise a TypeError because the `len()` method is not defined for strings y = len(x)

To fix this error, you can use the `str()` function to convert the string to an integer y = len(str(x))

By following these tips, you can help to avoid TypeErrors in your Python code.

4. Examples of TypeErrors

Here are some examples of TypeErrors:

x = ‘hello’ x[0] = ‘a’

This will result in a TypeError because strings are immutable and cannot be changed.

print(int(‘123’))

This will also result in a TypeError because the string ‘123’ cannot be converted to an integer.

class MyClass: def __init__(self, name): self.name = name

my_class = MyClass(‘John’) my_class.name = ‘Jane’

This will also result in a TypeError because the method `name` is not defined on the `MyClass` object.

TypeErrors are a common problem in Python, but they can be easily avoided by following the tips in this article. By using the correct data types, operators, and methods, you can help to ensure that your Python code is free of errors.

Q: What does the error “TypeError: type object does not support item assignment” mean?

A: This error occurs when you try to assign a value to a property of a type object. For example, the following code will raise an error:

>>> type = type(‘MyType’, (object,), {}) >>> type.name = ‘MyType’ Traceback (most recent call last): File “ “, line 1, in TypeError: type object does not support item assignment

The reason for this error is that type objects are immutable, which means that their properties cannot be changed after they are created. If you need to change the value of a property of a type object, you can create a new type object with the desired value.

Q: How can I fix the error “TypeError: type object does not support item assignment”?

A: There are two ways to fix this error. The first way is to create a new type object with the desired value. For example, the following code will fix the error in the example above:

>>> type = type(‘MyType’, (object,), {‘name’: ‘MyType’}) >>> type.name ‘MyType’

The second way to fix this error is to use a dictionary to store the properties of the type object. For example, the following code will also fix the error in the example above:

>>> type = type(‘MyType’, (object,), {}) >>> type.__dict__[‘name’] = ‘MyType’ >>> type.name ‘MyType’

Q: What are some common causes of the error “TypeError: type object does not support item assignment”?

A: There are a few common causes of this error. The first is trying to assign a value to a property of a type object that does not exist. For example, the following code will raise an error:

>>> type = type(‘MyType’, (object,), {}) >>> type.foo = ‘bar’ Traceback (most recent call last): File “ “, line 1, in AttributeError: type object has no attribute ‘foo’

The second is trying to assign a value to a property of a type object that is read-only. For example, the following code will also raise an error:

>>> type = type(‘MyType’, (object,), {}) >>> type.name = ‘MyType’ Traceback (most recent call last): File “ “, line 1, in TypeError: can’t set attribute ‘name’ of type object

The third is trying to assign a value to a property of a type object that is not a valid type. For example, the following code will also raise an error:

>>> type = type(‘MyType’, (object,), {}) >>> type.name = 123 Traceback (most recent call last): File “ “, line 1, in TypeError: can’t assign int to str object

Q: How can I avoid the error “TypeError: type object does not support item assignment”?

A: There are a few things you can do to avoid this error. First, make sure that you are trying to assign a value to a property of a type object that exists. Second, make sure that you are not trying to assign a value to a property of a type object that is read-only. Third, make sure that you are not trying to assign a value to a property of a type object that is not a valid type.

Here are some specific examples of how to avoid this error:

• Instead of trying to assign a value to the `name` property of a type object, you can create a new type object with the desired value. For example:

>>> type = type(‘MyType’, (object,), {‘name’: ‘MyType’})

• Instead of trying to assign a value to the `name` property of a type object, you can use a dictionary to store the properties of the type object. For example:

>>> type = type(‘MyType’, (object,), {}) >>> type.__dict__[‘name’] = ‘MyType’

• Instead of trying to assign a value to the `name` property of a type object, you can use a getter and setter method to access the property. For example:

In this blog post, we discussed the TypeError: type object does not support item assignment error. We first explained what the error is and then provided several ways to fix it. We also discussed some common causes of the error and how to avoid them.

We hope that this blog post has been helpful and that you now have a better understanding of the TypeError: type object does not support item assignment error. If you have any other questions or comments, please feel free to leave them below.

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【Python】TypeError: ‘NoneType’のエラー原因と対処法まとめ（初心者向け・実例でわかりやすく解説）

再帰関数などを使って処理を記述している場合に、次のようなエラーが発生することがあります。

なお、この記事の内容は、上記以外でも「NoneTpye」を含むエラー全般の発生原因と対処法にもなっています。

エラーが発生する状況例

対処法（returnの設置）, returnの設置場所の注意点.

最初に結論を述べると、主な原因は次の２つです。

①戻り値(return)のない関数の実行結果は「値None, タイプNoneType」になる。

②関数を変数に代入する場合は、その関数にreturnがあること。 　└ printではだめ。（実行結果ではなく、実行途中のいち処理のため） 　└ returnは関数の最終出力となっていること。 　└ 関数内のどこかにreturnが1個あればいいというわけではない。

以下で実例を踏まえて原因と対処法について解説しています。

例えば、次のように多次元配列からintを抜き出そうとしたときに、’NoneType’ object is not iterableのエラーが発生します。

‘NoneType’のオブジェクトをいじろうとしていることが原因です。

▼もう少し細かく 「res = number(brr)」で変数に関数number()代入しているが、この関数自体に戻り値(return)がないため、変数にはNoneが格納され、タイプがNoneTypeとなっている。

「result += res」このNoneTypeの変数resと、list型の変数resultを結合しようとしたため、

resはイテラブルじゃないから結合できないと言われている。

関数にデフォルト引数が渡されなかった場合に発生するエラー。値はNoneのみとのこと。

(python公式)Noneとは 型 NoneType の唯一の値です。 None は、関数にデフォルト引数が渡されなかったときなどに、値の非存在を表すのに頻繁に用いられます。 None への代入は不正で、SyntaxError を送出します。

▼簡単にするとこんな感じ 関数の実行結果が空とき、その結果自体がNoneTypeになる。

なので、実行結果が空の関数を変数に代入するとNoneTypeになる。

printの場合もNoneTypeになる

「こんにちは」が出力されているが、関数の実行過程で表示されたもので、関数自体と置き換わるものではない。

NoneTypeとしないために、returnで関数に実態をもたせる。 　└ 戻り値(return)は関数を実行した結果を関数自身と置き換える。

xが文字列「こんにちは」に置き換わっている。

関数の中にreturnがあればいいというわけではありません。実行した最終結果としてreturnを経由する必要があります。

▼returnが記述されているがNoneTypeになる例

1 < 2　のため、関数の出力結果は空になっている。この原因は、returnの処理を経由しないためです。

▼実行結果がreturnを経由する場合はOK

▼関数自体はのタイプはfunction

▼関数自体を変数に代入する場合はカッコ不要, ▼変数（関数を代入）の実行例.

hello()=x()となっている。

冒頭に記述したエラーコードを修正すると以下のようになります。

ポイントは、 変数に代入する値が関数にならないよう、returnを適切に設置する。

以上で無事に処理が動きます。

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TypeError: 'tuple' object does not support item assignment

Last updated: Apr 8, 2024 Reading time · 4 min

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

The Python "TypeError: 'tuple' object does not support item assignment" occurs when we try to change the value of an item in a tuple.

To solve the error, convert the tuple to a list, change the item at the specific index and convert the list back to a tuple.

Here is an example of how the error occurs.

We tried to update an element in a tuple, but tuple objects are immutable which caused the error.

# Convert the tuple to a list to solve the error

We cannot assign a value to an individual item of a tuple.

Instead, we have to convert the tuple to a list.

This is a three-step process:

• Use the list() class to convert the tuple to a list.
• Update the item at the specified index.
• Use the tuple() class to convert the list back to a tuple.

Once we have a list, we can update the item at the specified index and optionally convert the result back to a tuple.

Python indexes are zero-based, so the first item in a tuple has an index of 0 , and the last item has an index of -1 or len(my_tuple) - 1 .

# Constructing a new tuple with the updated element

Alternatively, you can construct a new tuple that contains the updated element at the specified index.

The get_updated_tuple function takes a tuple, an index and a new value and returns a new tuple with the updated value at the specified index.

The original tuple remains unchanged because tuples are immutable.

We updated the tuple element at index 1 , setting it to Z .

If you only have to do this once, you don't have to define a function.

The code sample achieves the same result without using a reusable function.

The values on the left and right-hand sides of the addition (+) operator have to all be tuples.

The syntax for tuple slicing is my_tuple[start:stop:step] .

The start index is inclusive and the stop index is exclusive (up to, but not including).

If the start index is omitted, it is considered to be 0 , if the stop index is omitted, the slice goes to the end of the tuple.

# Using a list instead of a tuple

Alternatively, you can declare a list from the beginning by wrapping the elements in square brackets (not parentheses).

Declaring a list from the beginning is much more efficient if you have to change the values in the collection often.

Tuples are intended to store values that never change.

# How tuples are constructed in Python

In case you declared a tuple by mistake, tuples are constructed in multiple ways:

• Using a pair of parentheses () creates an empty tuple
• Using a trailing comma - a, or (a,)
• Separating items with commas - a, b or (a, b)
• Using the tuple() constructor

# Checking if the value is a tuple

You can also handle the error by checking if the value is a tuple before the assignment.

If the variable stores a tuple, we set it to a list to be able to update the value at the specified index.

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

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

The type class returns the type of an object.

# Additional Resources

You can learn more about the related topics by checking out the following tutorials:

• How to convert a Tuple to an Integer in Python
• How to convert a Tuple to JSON in Python
• Find Min and Max values in Tuple or List of Tuples in Python
• Get the Nth element of a Tuple or List of Tuples in Python
• Creating a Tuple or a Set from user Input in Python
• How to Iterate through a List of Tuples in Python
• Write a List of Tuples to a File in Python
• AttributeError: 'tuple' object has no attribute X in Python
• TypeError: 'tuple' object is not callable in Python [Fixed]

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node children python TypeError: 'NoneType' object does not support item assignment #62

Mejituu commented Nov 15, 2023

Sorry, something went wrong.

stelcodes commented Jul 9, 2024

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python type() TypeError: 'str' object is not callable [closed]

I have the following code:

I get the following error:

Can someone please explain?

• 5 You need to provide a minimum reproducible example. The above code does not produce that error. You most likely defined type elsewhere. –  BTables Commented 2 days ago
• 7 You probably created a variable type which is shadowing the built-in function earlier in your program. –  flakes Commented 2 days ago

I just ran your code, and it didn't seem to have any errors.

So, I assume your problem is that you defined type somewhere earlier in the code like this:

Generally it's best practice if you do not define things that are functions or class.

• 4 See Why should I help close "bad" questions that I think are valid, instead of helping the OP with an answer? Phrased differently, this question might be reasonable to answer, but it should be closed in its present state due to the lack of a minimal reproducible example . –  Anerdw Commented 2 days ago

Not the answer you're looking for? Browse other questions tagged python typeerror or ask your own question .

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