tuple' object does not support item assignment stackoverflow

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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Tuple Object Does Not Support Item Assignment. Why?

Have you ever seen the error “tuple object does not support item assignment” when working with tuples in Python? In this article we will learn why this error occurs and how to solve it.

The error “tuple object does not support item assignment” is raised in Python when you try to modify an element of a tuple. This error occurs because tuples are immutable data types. It’s possible to avoid this error by converting tuples to lists or by using the tuple slicing operator.

Let’s go through few examples that will show you in which circumstances this error occurs and what to do about it.

Let’s get started!

Explanation of the Error “Tuple Object Does Not Support Item Assignment”

Define a tuple called cities as shown below:

If you had a list you would be able to update any elements in the list .

But, here is what happens if we try to update one element of a tuple:

Tuples are immutable and that’s why we see this error.

There is a workaround to this, we can:

• Convert the tuple into a list.
• Update any elements in the list.
• Convert the final list back to a tuple.

To convert the tuple into a list we will use the list() function :

Now, let’s update the element at index 1 in the same way we have tried to do before with the tuple:

You can see that the second element of the list has been updated.

Finally, let’s convert the list back to a tuple using the tuple() function :

Makes sense?

Avoid the “Tuple Object Does Not Support Item Assignment” Error with Slicing

The slicing operator also allows to avoid this error.

Let’s see how we can use slicing to create a tuple from our original tuple where only one element is updated.

We will use the following tuple and we will update the value of the element at index 2 to ‘Rome’.

Here is the result we want:

We can use slicing and concatenate the first two elements of the original tuple, the new value and the last two elements of the original tuple.

Here is the generic syntax of the slicing operator (in this case applied to a tuple).

This takes a slice of the tuple including the element at index n and excluding the element at index m .

Firstly, let’s see how to print the first two and last two elements of the tuple using slicing…

First two elements

We can also omit the first zero considering that the slice starts from the beginning of the tuple.

Last two elements

Notice that we have omitted index m considering that the slice includes up to the last element of the tuple.

Now we can create the new tuple starting from the original one using the following code:

(‘Rome’,) is a tuple with one element of type string.

Does “Tuple Object Does Not Support Item Assignment” Apply to a List inside a Tuple?

Let’s see what happens when one of the elements of a tuple is a list.

If we try to update the second element of the tuple we get the expected error:

If we try to assign a new list to the third element…

…once again we get back the error “‘ tuple’ object does not support item assignment “.

But if we append another number to the list inside the tuple, here is what happens:

The Python interpreter doesn’t raise any exceptions because the list is a mutable data type.

This concept is important for you to know when you work with data types in Python:

In Python, lists are mutable and tuples are immutable.

How to Solve This Error with a List of Tuples

Do we see this error also with a list of tuples?

Let’s say we have a list of tuples that is used in a game to store name and score for each user:

The user John has gained additional points and I want to update the points associated to his user:

When I try to update his points we get back the same error we have seen before when updating a tuple.

How can we get around this error?

Tuples are immutable but lists are mutable and we could use this concept to assign the new score to a new tuple in the list, at the same position of the original tuple in the list.

So, instead of updating the tuple at index 0 we will assign a new tuple to it.

Let’s see if it works…

It does work! Once again because a list is mutable .

And here is how we can make this code more generic?

Ok, this is a bit more generic because we didn’t have to provide the name of the user when updating his records.

This is just an example to show you how to address this TypeError , but in reality in this scenario I would prefer to use a dictionary instead.

It would allow us to access the details of each user from the name and to update the score without any issues.

Tuple Object Does Not Support Item Assignment Error With Values Returned by a Function

This error can also occur when a function returns multiple values and you try to directly modify the values returned by the function.

I create a function that returns two values: the number of users registered in our application and the number of users who have accessed our application in the last 30 days.

As you can see the two values are returned by the function as a tuple.

So, let’s assume there is a new registered user and because of that I try to update the value returned by the function directly.

I get the following error…

This can happen especially if I know that two values are returned by the function but I’m not aware that they are returned in a tuple.

Why Using Tuples If We Get This Error?

You might be thinking…

What is the point of using tuples if we get this error every time we try to update them?

Wouldn’t be a lot easier to always use lists instead?

We can see the fact that tuples are immutable as an added value for tuples when we have some data in our application that should never be modified.

Let’s say, for example, that our application integrates with an external system and it needs some configuration properties to connect to that system.

The tuple above contains two values: the API endpoint of the system we connect to and the port for their API.

We want to make sure this configuration is not modified by mistake in our application because it would break the integration with the external system.

So, if our code inadvertently updates one of the values, the following happens:

Remember, it’s not always good to have data structures you can update in your code whenever you want.

In this article we have seen when the error “tuple object does not support item assignment” occurs and how to avoid it.

You have learned how differently the tuple and list data types behave in Python and how you can use that in your programs.

If you have any questions feel free to post them in the comment below 🙂

Claudio Sabato is an IT expert with over 15 years of professional experience in Python programming, Linux Systems Administration, Bash programming, and IT Systems Design. He is a professional certified by the Linux Professional Institute .

With a Master’s degree in Computer Science, he has a strong foundation in Software Engineering and a passion for robotics with Raspberry Pi.

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Solve Python TypeError: 'tuple' object does not support item assignment

Consider the example below:

Solution #1: Change the tuple to list first

Solution #2: create a new tuple.

This tutorial shows you two easy solutions on how to change the tuple object element(s) and avoid the TypeError.

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Python typeerror: ‘tuple’ object does not support item assignment Solution

Tuples are immutable objects . “Immutable” means you cannot change the values inside a tuple. You can only remove them. If you try to assign a new value to an item in a variable, you’ll encounter the “typeerror: ‘tuple’ object does not support item assignment” error.

In this guide, we discuss what this error means and why you may experience it. We’ll walk through an example of this error so you can learn how to solve it in your code.

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Typeerror: ‘tuple’ object does not support item assignment.

While tuples and lists both store sequences of data, they have a few distinctions. Whereas you can change the values in a list, the values inside a tuple cannot be changed. Also, tuples are stored within parenthesis whereas lists are declared between square brackets.

Because you cannot change values in a tuple, item assignment does not work.

Consider the following code snippet:

This code snippet lets us change the first value in the “honor_roll” list to Holly. This works because lists are mutable. You can change their values. The same code does not work with data that is stored in a tuple.

An Example Scenario

Let’s build a program that tracks the courses offered by a high school. Students in their senior year are allowed to choose from a class but a few classes are being replaced.

Start by creating a collection of class names:

We’ve created a tuple that stores the names of each class being offered.

The science department has notified the school that psychology is no longer being offered due to a lack of numbers in the class. We’re going to replace psychology with philosophy as the philosophy class has just opened up a few spaces.

To do this, we use the assignment operator:

This code will replace the value at the index position 3 in our list of classes with “Philosophy”. Next, we print our list of classes to the console so that the user can see what classes are being actively offered:

Use a for loop to print out each class in our tuple to the console. Let’s run our code and see what happens:

Our code returns an error.

The Solution

We’ve tried to use the assignment operator to change a subject in our list. Tuples are immutable so we cannot change their values. This is why our code returns an error.

To solve this problem, we convert our “classes” tuple into a list . This will let us change the values in our sequence of class names.

Do this using the list() method:

We use the list() method to convert the value of “classes” to a list. We assign this new list to the variable “as_list”. Now that we have our list of classes stored as a list, we can change existing classes in the list.

Let’s run our code:

Our code successfully changes the “Psychology” class to “Philosophy”. Our code then prints out the list of classes to the console.

If we need to store our data as a tuple, we can always convert our list back to a tuple once we have changed the values we want to change. We can do this using the tuple() method:

This code converts “as_list” to a tuple and prints the value of our tuple to the console:

We could use this tuple later in our code if we needed our class names stored as a tuple.

The “typeerror: ‘tuple’ object does not support item assignment” error is raised when you try to change a value in a tuple using item assignment.

To solve this error, convert a tuple to a list before you change the values in a sequence. Optionally, you can then convert the list back to a tuple.

Now you’re ready to fix this error in your code like a pro !

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Python Tuple does not support item assignment

5 minute read

Introduction

In Python, tuples are immutable, meaning that their elements cannot be modified once they have been assigned. This means that attempting to assign a value to an element in a tuple will result in the following error:

TypeError: ‘tuple’ object does not support item assignment

This error can be frustrating, but there are a few ways to work around it and achieve the desired outcome. In this article, we will explore three different ways to fix this error and give an in-depth explanation of how each method works.

Error and Cause

When attempting to reassign an item in a tuple using the indexing operator, such as:

Python will raise a TypeError, indicating that the tuple object does not support item assignment. This is because, as previously mentioned, tuples are immutable , and their elements cannot be modified once they have been assigned.

Python’s tuple is a built-in data structure that can store multiple values in a single object. This makes it useful for situations where you need to store multiple related values together.

Tuples are defined by enclosing the values in parentheses and separating them with commas. For example, the following code creates a tuple with three integers:

This tuple object, as stated before, is immutable, which means that once it is created, its elements cannot be modified. This means that you cannot add, remove, or change the values of the elements in a tuple.

This is why when you try to reassign a value to an element in the tuple using the indexing operator, such as my_tuple[0] = 4, python will raise a TypeError, indicating that the tuple object does not support item assignment.

Fix 1: Convert Tuple to List

One way to fix this error is to convert the tuple to a list, make the desired changes, and then convert it back to a tuple.

In the above example, we first convert the tuple to a list using the built-in list() function. Once the tuple is converted to a list, we can use the indexing operator to reassign the value at index 0 to 4.

Since lists are mutable, this operation is allowed. Once the desired changes have been made, we convert the list back to a tuple using the built-in tuple() function. The original tuple object is now replaced by the new tuple object which has the desired value at index 0.

It’s important to note that the original tuple remains unchanged, and the new tuple is created with the modified values. This method is useful when you want to make changes to the tuple and need to keep the original tuple object intact.

Fix 2: Using Slicing

Another way to change the values in a tuple is by using slicing. You can create a new tuple with the desired values by slicing the original tuple and concatenating the new values.

In this example, we use slicing to create a new tuple. The my_tuple[:0] slice returns an empty tuple, the (4,) creates a new tuple with the value 4, and the my_tuple[1:] slice returns a new tuple with all elements of the original tuple except the first element.

We then concatenate these three tuples using the + operator to create a new tuple with the desired values.

It’s important to note that the original tuple remains unchanged, and the new tuple is created with the modified values.

This method is useful when you want to make changes to the tuple and need to keep the original tuple object intact.

It is also worth noting that this method is the most efficient one of the three, as it only uses slicing which has O(k) time complexity where k is the number of elements in the slice.

Fix 3: Creating a new Tuple

The last fix is creating a new tuple with the desired values.

This method works similarly to the previous method, but instead of using slicing and concatenation, we create a new tuple with the desired value and concatenate it with the rest of the elements of the original tuple using the + operator.

While tuples are immutable in Python, there are a few ways to work around the ‘tuple’ object does not support item assignment error. By converting the tuple to a list, using slicing, or creating a new tuple, you can achieve the desired outcome.

We hope this article was useful.

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ArcPy Update Cursor after nested Search Cursor giving tuple assignment error?

I am running ArcMap 10.4.1. I am running a script that uses a DA search cursor nested inside an update cursor to assign variables from values in a table. The script then writes those same variables to a feature class in the update cursor. I have done this many times in the past, but now I am getting a tuple assignment error when I try to assign row values in the update cursor. I know tuples aren't mutable and I am not trying to assign values in the search cursor. What is the problem here? This syntax has worked many times in the past.

The script fails on the first attempted row assignment after the search cursor:

row[2] = tblAppAdd TypeError: 'tuple' object does not support item assignment

Here is the script portion (edited for length):

• arcgis-10.4

• 2 Try calling your SearchCursor iterator something like sRow since you're already using row for the UpdateCursor. –  Evan Oct 25, 2016 at 20:25
• 5 Nested cursors are generally frowned upon. The typical approach is to use a search cursor first to create a dictionary of the key/value pairs you need (in your case from tblPatients), then reference the dictionary from within the update cursor. –  Bjorn Oct 25, 2016 at 20:41

First, you reassigned row. Change row to srow for the search cursor and row to urow for the update cursor.

The error you're getting is that you're trying to update the search cursor object (since it got reassigned). The arcpy.da.search cursor returns a tuple, and update cursor returns a list.

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TypeError: ‘tuple’ object does not support item assignment: How to Fix

Have you ever tried to assign a value to a specific element of a tuple in Python, only to get an error message like “TypeError: ‘tuple’ object does not support item assignment”? If so, you’re not alone. This is a common error that can be confusing for beginners, but it’s actually pretty easy to understand once you know what’s going on.

In this article, we’ll take a closer look at what a tuple is, why you can’t assign values to individual elements of a tuple, and how you can work around this limitation. We’ll also provide some examples of how to use tuples effectively in your Python code.

So if you’re ready to learn more about tuples and how to avoid the “TypeError: ‘tuple’ object does not support item assignment” error, keep reading!

| Column 1 | Column 2 | Column 3 | |—|—|—| | Error | `TypeError: ‘tuple’ object does not support item assignment` | An error that occurs when you try to assign a value to an item in a tuple. | | Cause | The cause of this error is that tuples are immutable, which means that you cannot change their values after they have been created. | | Solution | To fix this error, you can either convert the tuple to a list, or you can use a different data type, such as a dictionary or a set. |

A TypeError is a type of error that occurs when an operation is attempted on an object of an incorrect type. For example, trying to assign a value to an element of a tuple will result in a TypeError.

This error can be avoided by ensuring that the objects you are working with are of the correct type. For example, if you want to assign a value to an element of a tuple, you can use the `append()` method to add the value to the end of the tuple.

**What causes a TypeError?**

A TypeError can be caused by a number of things, including:

• Trying to use an operator that is not supported for the given type of object.
• Trying to access an element of an object that does not exist.
• Trying to assign a value to an object that is immutable.

**Trying to use an operator that is not supported for the given type of object**

One common cause of a TypeError is trying to use an operator that is not supported for the given type of object. For example, the `+` operator can be used to add two numbers together, but it cannot be used to add a string to a number.

python >>> 1 + ‘2’ TypeError: unsupported operand type(s) for +: ‘int’ and ‘str’

To avoid this type of error, make sure that you are using the correct operators for the types of objects you are working with.

**Trying to access an element of an object that does not exist**

Another common cause of a TypeError is trying to access an element of an object that does not exist. For example, the following code will result in a TypeError because the `index` 0 does not exist in the `list` `my_list`:

python >>> my_list = [‘a’, ‘b’, ‘c’] >>> my_list[0] ‘a’ >>> my_list[1] ‘b’ >>> my_list[2] ‘c’ >>> my_list[3] Traceback (most recent call last): File “ “, line 1, in IndexError: list index out of range

To avoid this type of error, make sure that you are checking the index of the element you are trying to access before you try to access it.

**Trying to assign a value to an object that is immutable**

Finally, a TypeError can also be caused by trying to assign a value to an object that is immutable. An immutable object is an object whose value cannot be changed after it has been created. For example, strings and numbers are immutable objects.

python >>> my_string = ‘hello’ >>> my_string[0] = ‘j’ Traceback (most recent call last): File “ “, line 1, in TypeError: ‘str’ object does not support item assignment

To avoid this type of error, make sure that you are not trying to assign a value to an immutable object.

A TypeError is a type of error that occurs when an operation is attempted on an object of an incorrect type. This error can be avoided by ensuring that the objects you are working with are of the correct type and that you are not trying to access elements of an object that do not exist or assign values to immutable objects.

Here are some additional tips for avoiding TypeErrors:

• Use the `type()` function to check the type of an object before you try to perform an operation on it.
• Use the `len()` function to check the length of a list or tuple before you try to access an element that is out of range.
• Use the `isinstance()` function to check whether an object is of a particular type.

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

What is a TypeError?

A TypeError occurs when you try to use an operator or function on an object that does not support it. For example, you cannot use the `+` operator to add two strings together, because strings are immutable.

How to fix a TypeError?

To fix a TypeError, you need to identify the cause of the error and correct it. This may involve:

• Using the correct operator for the given type of object.
• Checking that the object you are trying to access exists.
• Using a different type of object that is mutable.

Examples of TypeErrors

Here are some examples of TypeErrors:

>>> tuple = (1, 2, 3) >>> tuple[0] = 4 TypeError: ‘tuple’ object does not support item assignment

>>> list = [1, 2, 3] >>> list[0] = ‘4’ TypeError: can’t convert ‘int’ object to str implicitly

>>> dict = {‘a’: 1, ‘b’: 2} >>> dict[‘c’] = 3 KeyError: ‘c’

In the first example, we try to assign the value 4 to the first element of the tuple `tuple`. However, tuples are immutable, which means that their values cannot be changed. This results in a TypeError.

In the second example, we try to convert the integer 1 to a string and assign it to the first element of the list `list`. However, the `int` type cannot be converted to the `str` type implicitly. This results in a TypeError.

In the third example, we try to access the key `c` in the dictionary `dict`. However, the key `c` does not exist in the dictionary. This results in a KeyError.

TypeErrors can be avoided by using the correct operators and functions for the given type of object. It is also important to check that the object you are trying to access exists before trying to access it.

If you are still getting TypeErrors, you can try using a different type of object that is mutable. For example, if you are trying to add two strings together, you can use the `join()` method to join the two strings into one.

Here are some additional resources that you may find helpful:

• [Python TypeErrors](https://docs.python.org/3/library/exceptions.htmltypeerror)
• [How to Fix Python TypeErrors](https://www.w3schools.com/python/python_errors_typeerror.asp)

A: This error occurs when you try to assign a value to an item in a tuple. Tuples are immutable, which means that their values cannot be changed after they are created. Therefore, you cannot use the assignment operator (=) to assign a new value to an item in a tuple.

Q: How can I avoid this error? A: There are a few ways to avoid this error.

• Use a list instead of a tuple. Lists are mutable, which means that their values can be changed after they are created. Therefore, you can use the assignment operator (=) to assign new values to items in a list.
• Use the slice operator ([]) to access items in a tuple. The slice operator allows you to access a range of items in a tuple. This can be useful if you need to change multiple items in a tuple at once.
• Use the `tuple()` function to create a new tuple with the desired values. This can be useful if you need to create a tuple with the same values as an existing tuple, but with the ability to change the values later.

Q: Can I still use tuples if I need to be able to change their values? A: Yes, you can still use tuples if you need to be able to change their values. However, you will need to use a different data structure, such as a list or a dictionary.

Q: What are some other common errors related to tuples? A: Some other common errors related to tuples include:

• Trying to access an item in a tuple that does not exist. This will result in a `KeyError` exception.
• Trying to add an item to a tuple. This will result in a `TypeError` exception.
• Trying to delete an item from a tuple. This will result in a `TypeError` exception.

Q: Where can I learn more about tuples? A: You can learn more about tuples by reading the following resources:

• [The Python Tutorial: Tuples](https://docs.python.org/3/tutorial/datastructures.htmltuples)
• [Stack Overflow: Tuples](https://stackoverflow.com/questions/tagged/tuples)

We hope that this blog post has been helpful. If you have any other questions about tuples or this error, please feel free to leave a comment below.

Here are some key takeaways from this blog post:

• A tuple is a collection of immutable objects, while a list is a collection of mutable objects.
• When you try to assign a value to an element of a tuple, you will get a TypeError: ‘tuple’ object does not support item assignment.
• To get around this error, you can use list comprehension or the tuple() function.
• For more information on tuples, please see the Python documentation.

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How to Solve Python TypeError: ‘tuple’ object does not support item assignment

by Suf | Programming , Python , Tips

Tuples are immutable objects, which means you cannot change them once created. If you try to change a tuple in place using the indexing operator [], you will raise the TypeError: ‘tuple’ object does not support item assignment.

To solve this error, you can convert the tuple to a list, perform an index assignment then convert the list back to a tuple.

This tutorial will go through how to solve this error and solve it with the help of code examples.

Table of contents

Typeerror: ‘tuple’ object does not support item assignment.

Let’s break up the error message to understand what the error means. TypeError occurs whenever you attempt to use an illegal operation for a specific data type.

The part 'tuple' object tells us that the error concerns an illegal operation for tuples.

The part does not support item assignment tells us that item assignment is the illegal operation we are attempting.

Tuples are immutable objects, which means we cannot change them once created. We have to convert the tuple to a list, a mutable data type suitable for item assignment.

Let’s look at an example of assigning items to a list. We will iterate over a list and check if each item is even. If the number is even, we will assign the square of that number in place at that index position.

Let’s run the code to see the result:

We can successfully do item assignments on a list.

Let’s see what happens when we try to change a tuple using item assignment:

We throw the TypeError because the tuple object is immutable.

To solve this error, we need to convert the tuple to a list then perform the item assignment. We will then convert the list back to a tuple. However, you can leave the object as a list if you do not need a tuple.

Let’s run the code to see the updated tuple:

Congratulations on reading to the end of this tutorial. The TypeError: ‘tuple’ object does not support item assignment occurs when you try to change a tuple in-place using the indexing operator [] . You cannot modify a tuple once you create it. To solve this error, you need to convert the tuple to a list, update it, then convert it back to a tuple.

For further reading on TypeErrors, go to the article:

• How to Solve Python TypeError: ‘str’ object does not support item assignment

To learn more about Python for data science and machine learning, go to the  online courses page on Python  for the most comprehensive courses available.

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Split tuples with labeled samples in training, validation and test sets

I was reading through all the internet and i can't find nothing similar what i am looking for, i only saw this topic for pd.DataFrame, np.ndarray and list datasets but i didn't find nothing explaining about the technique for tuples of (sample, target), in my real project i collected some text values from a sensor data, treated these values to convert them in floats and numpy arrays after and for each data i put the label values manually by hand according his class. Initially, i based myself in the MNIST example from the (mnist.pkl.gz) file where i realized that each digit(sample) has a corresponding label value for it and it was splitted in training, validation and test data (tuples), and after, each one of them was splitted in numpy.ndarray data corresponding the samples(float32) and labels(int64) and i am trying to do it through this algorithm:

here is the content of x_sample:

and x_label:

But it's giving to me this error: TypeError: 'tuple' object does not support item assignment

I already tried through np.split:

and another error was displayed:

AttributeError: 'tuple' object has no attribute 'sample'

I am trying to split it in 60% training, 20% validation and 20% test. This example isn't about my real project, but it is related the same idea, the dataset from my project is very large to put here, is there any suggestion that i could do to split tuples of related data(input and target) into these sets?

• neural-network
• multilabel-classification

I would suggest using the well-known and tested train_test_split function from sklearn . Here is the documentation .

You start with arrays in your example, so no need to use tuples.

Because you want train, test and validation sets, you will need to split the data twice though. Here is an example, where I split the into train_and_val and test , then split the train_and_val part into (final) train and val . The test remains from the first split to leave you with a final 60-20-20 split:

To split the 80 from above into 60-20 of the entire dataset, we need to use a test_size of $20 / (60 + 20) = 0.25$ .

Now you have X_train , y_train (60%), X_val , y_val (20%) and X_test , y_test (60%).

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While resizing an object by script: 'tuple' object does not support item assignment

When using this code, I've an error, I think it's about tuples being immutable, but I can't understand why. I'm looking to resize the cube just created:

The error message:

TypeError: 'tuple' object does not support item assignment

Any help appreciated.

Works fine here, maybe that's an error from a previous state in your script. It does not come from this snippet.

The error message

is something you might get if you have the following code

tuples are immutable, if you want to modify an individual element's value then you use a list .

• $\begingroup$ Thanks for your time. The problem wasn't actually on this line, my mistake. I'll select your answer because this may actually help someone else with this error message. $\endgroup$ –  mins Jan 3, 2016 at 17:43

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• Python »
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• 5. Data Structures
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5. Data Structures ¶

This chapter describes some things you’ve learned about already in more detail, and adds some new things as well.

5.1. More on Lists ¶

The list data type has some more methods. Here are all of the methods of list objects:

Add an item to the end of the list. Equivalent to a[len(a):] = [x] .

Extend the list by appending all the items from the iterable. Equivalent to a[len(a):] = iterable .

Insert an item at a given position. The first argument is the index of the element before which to insert, so a.insert(0, x) inserts at the front of the list, and a.insert(len(a), x) is equivalent to a.append(x) .

Remove the first item from the list whose value is equal to x . It raises a ValueError if there is no such item.

Remove the item at the given position in the list, and return it. If no index is specified, a.pop() removes and returns the last item in the list. It raises an IndexError if the list is empty or the index is outside the list range.

Remove all items from the list. Equivalent to del a[:] .

Return zero-based index in the list of the first item whose value is equal to x . Raises a ValueError if there is no such item.

The optional arguments start and end are interpreted as in the slice notation and are used to limit the search to a particular subsequence of the list. The returned index is computed relative to the beginning of the full sequence rather than the start argument.

Return the number of times x appears in the list.

Sort the items of the list in place (the arguments can be used for sort customization, see sorted() for their explanation).

Reverse the elements of the list in place.

Return a shallow copy of the list. Equivalent to a[:] .

An example that uses most of the list methods:

You might have noticed that methods like insert , remove or sort that only modify the list have no return value printed – they return the default None . [ 1 ] This is a design principle for all mutable data structures in Python.

Another thing you might notice is that not all data can be sorted or compared. For instance, [None, 'hello', 10] doesn’t sort because integers can’t be compared to strings and None can’t be compared to other types. Also, there are some types that don’t have a defined ordering relation. For example, 3+4j < 5+7j isn’t a valid comparison.

5.1.1. Using Lists as Stacks ¶

The list methods make it very easy to use a list as a stack, where the last element added is the first element retrieved (“last-in, first-out”). To add an item to the top of the stack, use append() . To retrieve an item from the top of the stack, use pop() without an explicit index. For example:

5.1.2. Using Lists as Queues ¶

It is also possible to use a list as a queue, where the first element added is the first element retrieved (“first-in, first-out”); however, lists are not efficient for this purpose. While appends and pops from the end of list are fast, doing inserts or pops from the beginning of a list is slow (because all of the other elements have to be shifted by one).

To implement a queue, use collections.deque which was designed to have fast appends and pops from both ends. For example:

5.1.3. List Comprehensions ¶

List comprehensions provide a concise way to create lists. Common applications are to make new lists where each element is the result of some operations applied to each member of another sequence or iterable, or to create a subsequence of those elements that satisfy a certain condition.

For example, assume we want to create a list of squares, like:

Note that this creates (or overwrites) a variable named x that still exists after the loop completes. We can calculate the list of squares without any side effects using:

or, equivalently:

which is more concise and readable.

A list comprehension consists of brackets containing an expression followed by a for clause, then zero or more for or if clauses. The result will be a new list resulting from evaluating the expression in the context of the for and if clauses which follow it. For example, this listcomp combines the elements of two lists if they are not equal:

and it’s equivalent to:

Note how the order of the for and if statements is the same in both these snippets.

If the expression is a tuple (e.g. the (x, y) in the previous example), it must be parenthesized.

List comprehensions can contain complex expressions and nested functions:

5.1.4. Nested List Comprehensions ¶

The initial expression in a list comprehension can be any arbitrary expression, including another list comprehension.

Consider the following example of a 3x4 matrix implemented as a list of 3 lists of length 4:

The following list comprehension will transpose rows and columns:

As we saw in the previous section, the inner list comprehension is evaluated in the context of the for that follows it, so this example is equivalent to:

which, in turn, is the same as:

In the real world, you should prefer built-in functions to complex flow statements. The zip() function would do a great job for this use case:

See Unpacking Argument Lists for details on the asterisk in this line.

5.2. The del statement ¶

There is a way to remove an item from a list given its index instead of its value: the del statement. This differs from the pop() method which returns a value. The del statement can also be used to remove slices from a list or clear the entire list (which we did earlier by assignment of an empty list to the slice). For example:

del can also be used to delete entire variables:

Referencing the name a hereafter is an error (at least until another value is assigned to it). We’ll find other uses for del later.

5.3. Tuples and Sequences ¶

We saw that lists and strings have many common properties, such as indexing and slicing operations. They are two examples of sequence data types (see Sequence Types — list, tuple, range ). Since Python is an evolving language, other sequence data types may be added. There is also another standard sequence data type: the tuple .

A tuple consists of a number of values separated by commas, for instance:

As you see, on output tuples are always enclosed in parentheses, so that nested tuples are interpreted correctly; they may be input with or without surrounding parentheses, although often parentheses are necessary anyway (if the tuple is part of a larger expression). It is not possible to assign to the individual items of a tuple, however it is possible to create tuples which contain mutable objects, such as lists.

Though tuples may seem similar to lists, they are often used in different situations and for different purposes. Tuples are immutable , and usually contain a heterogeneous sequence of elements that are accessed via unpacking (see later in this section) or indexing (or even by attribute in the case of namedtuples ). Lists are mutable , and their elements are usually homogeneous and are accessed by iterating over the list.

A special problem is the construction of tuples containing 0 or 1 items: the syntax has some extra quirks to accommodate these. Empty tuples are constructed by an empty pair of parentheses; a tuple with one item is constructed by following a value with a comma (it is not sufficient to enclose a single value in parentheses). Ugly, but effective. For example:

The statement t = 12345, 54321, 'hello!' is an example of tuple packing : the values 12345 , 54321 and 'hello!' are packed together in a tuple. The reverse operation is also possible:

This is called, appropriately enough, sequence unpacking and works for any sequence on the right-hand side. Sequence unpacking requires that there are as many variables on the left side of the equals sign as there are elements in the sequence. Note that multiple assignment is really just a combination of tuple packing and sequence unpacking.

5.4. Sets ¶

Python also includes a data type for sets . A set is an unordered collection with no duplicate elements. Basic uses include membership testing and eliminating duplicate entries. Set objects also support mathematical operations like union, intersection, difference, and symmetric difference.

Curly braces or the set() function can be used to create sets. Note: to create an empty set you have to use set() , not {} ; the latter creates an empty dictionary, a data structure that we discuss in the next section.

Here is a brief demonstration:

Similarly to list comprehensions , set comprehensions are also supported:

5.5. Dictionaries ¶

Another useful data type built into Python is the dictionary (see Mapping Types — dict ). Dictionaries are sometimes found in other languages as “associative memories” or “associative arrays”. Unlike sequences, which are indexed by a range of numbers, dictionaries are indexed by keys , which can be any immutable type; strings and numbers can always be keys. Tuples can be used as keys if they contain only strings, numbers, or tuples; if a tuple contains any mutable object either directly or indirectly, it cannot be used as a key. You can’t use lists as keys, since lists can be modified in place using index assignments, slice assignments, or methods like append() and extend() .

It is best to think of a dictionary as a set of key: value pairs, with the requirement that the keys are unique (within one dictionary). A pair of braces creates an empty dictionary: {} . Placing a comma-separated list of key:value pairs within the braces adds initial key:value pairs to the dictionary; this is also the way dictionaries are written on output.

The main operations on a dictionary are storing a value with some key and extracting the value given the key. It is also possible to delete a key:value pair with del . If you store using a key that is already in use, the old value associated with that key is forgotten. It is an error to extract a value using a non-existent key.

Performing list(d) on a dictionary returns a list of all the keys used in the dictionary, in insertion order (if you want it sorted, just use sorted(d) instead). To check whether a single key is in the dictionary, use the in keyword.

Here is a small example using a dictionary:

The dict() constructor builds dictionaries directly from sequences of key-value pairs:

In addition, dict comprehensions can be used to create dictionaries from arbitrary key and value expressions:

When the keys are simple strings, it is sometimes easier to specify pairs using keyword arguments:

5.6. Looping Techniques ¶

When looping through dictionaries, the key and corresponding value can be retrieved at the same time using the items() method.

When looping through a sequence, the position index and corresponding value can be retrieved at the same time using the enumerate() function.

To loop over two or more sequences at the same time, the entries can be paired with the zip() function.

To loop over a sequence in reverse, first specify the sequence in a forward direction and then call the reversed() function.

To loop over a sequence in sorted order, use the sorted() function which returns a new sorted list while leaving the source unaltered.

Using set() on a sequence eliminates duplicate elements. The use of sorted() in combination with set() over a sequence is an idiomatic way to loop over unique elements of the sequence in sorted order.

It is sometimes tempting to change a list while you are looping over it; however, it is often simpler and safer to create a new list instead.

5.7. More on Conditions ¶

The conditions used in while and if statements can contain any operators, not just comparisons.

The comparison operators in and not in are membership tests that determine whether a value is in (or not in) a container. The operators is and is not compare whether two objects are really the same object. All comparison operators have the same priority, which is lower than that of all numerical operators.

Comparisons can be chained. For example, a < b == c tests whether a is less than b and moreover b equals c .

Comparisons may be combined using the Boolean operators and and or , and the outcome of a comparison (or of any other Boolean expression) may be negated with not . These have lower priorities than comparison operators; between them, not has the highest priority and or the lowest, so that A and not B or C is equivalent to (A and (not B)) or C . As always, parentheses can be used to express the desired composition.

The Boolean operators and and or are so-called short-circuit operators: their arguments are evaluated from left to right, and evaluation stops as soon as the outcome is determined. For example, if A and C are true but B is false, A and B and C does not evaluate the expression C . When used as a general value and not as a Boolean, the return value of a short-circuit operator is the last evaluated argument.

It is possible to assign the result of a comparison or other Boolean expression to a variable. For example,

Note that in Python, unlike C, assignment inside expressions must be done explicitly with the walrus operator := . This avoids a common class of problems encountered in C programs: typing = in an expression when == was intended.

5.8. Comparing Sequences and Other Types ¶

Sequence objects typically may be compared to other objects with the same sequence type. The comparison uses lexicographical ordering: first the first two items are compared, and if they differ this determines the outcome of the comparison; if they are equal, the next two items are compared, and so on, until either sequence is exhausted. If two items to be compared are themselves sequences of the same type, the lexicographical comparison is carried out recursively. If all items of two sequences compare equal, the sequences are considered equal. If one sequence is an initial sub-sequence of the other, the shorter sequence is the smaller (lesser) one. Lexicographical ordering for strings uses the Unicode code point number to order individual characters. Some examples of comparisons between sequences of the same type:

Note that comparing objects of different types with < or > is legal provided that the objects have appropriate comparison methods. For example, mixed numeric types are compared according to their numeric value, so 0 equals 0.0, etc. Otherwise, rather than providing an arbitrary ordering, the interpreter will raise a TypeError exception.

Table of Contents

• 5.1.1. Using Lists as Stacks
• 5.1.2. Using Lists as Queues
• 5.1.3. List Comprehensions
• 5.1.4. Nested List Comprehensions
• 5.2. The del statement
• 5.3. Tuples and Sequences
• 5.5. Dictionaries
• 5.6. Looping Techniques
• 5.7. More on Conditions
• 5.8. Comparing Sequences and Other Types

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Providing a list to a function

I've never come across this problem until now and can't think how to proceed. I would like to know how to provide each element of a tuple to a function that wants individual parameters:

but calling it with:

This is probably beside the point, but the application has to do with drawing with PyQt's QPainter and providing the coordinates in a list (mylist, in the code below):

Thank you for any help.

• You can change p.drawLine(line) to p.drawLine(*line) .
• Also, you probably want to pass the line as a list() not tuple() (note that list = (1,2,3,4) is not a list() .):

What's the difference between lists and tuples?

• Yeah, sorry, used the WRONG terminology and I've changed the answer, to reflect your correction. Thank you so much for the help @User24714692 –  John 2 days ago

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