[Fixed] ModuleNotFoundError: No module named ‘tomli-w’

Quick Fix: Python raises the ImportError: No module named 'tomli-w' when it cannot find the library tomli-w. The most frequent source of this error is that you haven’t installed tomli-w explicitly with pip install tomli-w. Alternatively, you may have different Python versions on your computer, and tomli-w is not installed for the particular version you’re using.

In particular, you can try any of the following commands, depending on your concrete environment and installation needs:

💡 If you have only one version of Python installed:
pip install tomli-w

💡 If you have Python 3 (and, possibly, other versions) installed:
pip3 install tomli-w

💡 If you don't have PIP or it doesn't work
python -m pip install tomli-w
python3 -m pip install tomli-w

💡 If you have Linux and you need to fix permissions (any one):
sudo pip3 install tomli-w
pip3 install tomli-w --user

💡 If you have Linux with apt
sudo apt install tomli-w

💡 If you have Windows and you have set up the py alias
py -m pip install tomli-w

💡 If you have Anaconda
conda install -c anaconda tomli-w

💡 If you have Jupyter Notebook
!pip install tomli-w
!pip3 install tomli-w

Problem Formulation

You’ve just learned about the awesome capabilities of the tomli-w library and you want to try it out, so you start your code with the following statement:

import tomli-w

This is supposed to import the tomli-w library into your (virtual) environment. However, it only throws the following ImportError: No module named tomli-w:

>>> import tomli-w
Traceback (most recent call last):
  File "<pyshell#6>", line 1, in <module>
    import tomli-w
ModuleNotFoundError: No module named 'tomli-w'

Solution Idea 1: Install Library tomli-w

The most likely reason is that Python doesn’t provide tomli-w in its standard library. You need to install it first!

Before being able to import the tomli-w module, you need to install it using Python’s package manager pip. Make sure pip is installed on your machine.

To fix this error, you can run the following command in your Windows shell:

$ pip install tomli-w

This simple command installs tomli-w in your virtual environment on Windows, Linux, and MacOS. It assumes that your pip version is updated. If it isn’t, use the following two commands in your terminal, command line, or shell (there’s no harm in doing it anyways):

$ python -m pip install --upgrade pip
$ pip install tomli-w

💡 Note: Don’t copy and paste the $ symbol. This is just to illustrate that you run it in your shell/terminal/command line.

Solution Idea 2: Fix the Path

The error might persist even after you have installed the tomli-w library. This likely happens because pip is installed but doesn’t reside in the path you can use. Although pip may be installed on your system the script is unable to locate it. Therefore, it is unable to install the library using pip in the correct path.

To fix the problem with the path in Windows follow the steps given next.

Step 1: Open the folder where you installed Python by opening the command prompt and typing where python

Step 2: Once you have opened the Python folder, browse and open the Scripts folder and copy its location. Also verify that the folder contains the pip file.

Step 3: Now open the Scripts directory in the command prompt using the cd command and the location that you copied previously.

Step 4: Now install the library using pip install tomli-w command. Here’s an analogous example:

After having followed the above steps, execute our script once again. And you should get the desired output.

Understanding the “import” Statement

import tomli-w

In Python, the import statement serves two main purposes:

Search the module by its name, load it, and initialize it.
Define a name in the local namespace within the scope of the import statement. This local name is then used to reference the accessed module throughout the code.

What’s the Difference Between ImportError and ModuleNotFoundError?

What’s the difference between ImportError and ModuleNotFoundError?

Python defines an error hierarchy, so some error classes inherit from other error classes. In our case, the ModuleNotFoundError is a subclass of the ImportError class.

You can see this in this screenshot from the docs:

You can also check this relationship using the issubclass() built-in function:

>>> issubclass(ModuleNotFoundError, ImportError)
True

Specifically, Python raises the ModuleNotFoundError if the module (e.g., tomli-w) cannot be found. If it can be found, there may be a problem loading the module or some specific files within the module. In those cases, Python would raise an ImportError.

If an import statement cannot import a module, it raises an ImportError. This may occur because of a faulty installation or an invalid path. In Python 3.6 or newer, this will usually raise a ModuleNotFoundError.

How to Fix “ModuleNotFoundError: No module named ‘tomli-w'” in PyCharm

If you create a new Python project in PyCharm and try to import the tomli-w library, it’ll raise the following error message:

Traceback (most recent call last):
  File "C:/Users/.../main.py", line 1, in <module>
    import tomli-w
ModuleNotFoundError: No module named 'tomli-w'

Process finished with exit code 1

The reason is that each PyCharm project, per default, creates a virtual environment in which you can install custom Python modules. But the virtual environment is initially empty—even if you’ve already installed tomli-w on your computer!

Here’s a screenshot exemplifying this for the pandas library. It’ll look similar for tomli-w.

The fix is simple: Use the PyCharm installation tooltips to install Pandas in your virtual environment—two clicks and you’re good to go!

First, right-click on the pandas text in your editor:

Second, click “Show Context Actions” in your context menu. In the new menu that arises, click “Install Pandas” and wait for PyCharm to finish the installation.

The code will run after your installation completes successfully.

As an alternative, you can also open the Terminal tool at the bottom and type:

$ pip install tomli-w

If this doesn’t work, you may want to set the Python interpreter to another version using the following tutorial: https://www.jetbrains.com/help/pycharm/2016.1/configuring-python-interpreter-for-a-project.html

You can also manually install a new library such as tomli-w in PyCharm using the following procedure:

Open File > Settings > Project from the PyCharm menu.
Select your current project.
Click the Python Interpreter tab within your project tab.
Click the small + symbol to add a new library to the project.
Now type in the library to be installed, in your example Pandas, and click Install Package.
Wait for the installation to terminate and close all popup windows.

Here’s an analogous example:

Here’s a full guide on how to install a library on PyCharm.

How to Install a Library on PyCharm