How to Solve ModuleNotFoundError in Python

1. Use the Correct Module Name to Solve ModuleNotFoundError in Python
2. Use the Correct Syntax to Solve ModuleNotFoundError in Python

Modules are important for developing Python programs. With modules, we can separate different parts of a codebase for easier management.

When working with modules, understanding how they work and how we can import them into our code is important. Without this understanding or mistakes, we may experience different errors.

One example of such an error is ModuleNotFoundError. In this article, we will discuss the way to resolve ModuleNotFoundError within Python.

Use the Correct Module Name to Solve ModuleNotFoundError in Python

Let’s create a simple Python codebase with two files, index.py and file.py, where we import file.py into the index.py file. Both files are within the same directory.

The file.py file contains the code below.

class Student:
    def __init__(self, firstName, lastName):
        self.firstName = firstName
        self.lastName = lastName

The index.py file contains the code below.

import fiIe

studentOne = fiIe.Student("Isaac", "Asimov")
print(studentOne.lastName)

Now, let’s run index.py. The output of our code execution is below.

Traceback (most recent call last):
  File "c:\Users\akinl\Documents\Python\index.py", line 1, in <module>
    import fiIe
ModuleNotFoundError: No module named 'fiIe'

We have a ModuleNotFoundError. If you look closely, you will notice that the import statement has a typographical error where file is written as fiIe with the l replaced with a capital I.

Therefore, if we use the wrong name, a ModuleNotFoundError can be thrown at us. Be careful when writing your module names.

Now, let’s correct it and get our code running.

import file

studentOne = file.Student("Isaac", "Asimov")
print(studentOne.lastName)

The output of the code:

Asimov

Also, we could rewrite the import statement using the from keyword and import just the Student class. This is useful for cases where we don’t want to import all the functions, classes, and methods present within the module.

from file import Student

studentOne = Student("Isaac", "Asimov")
print(studentOne.lastName)

We will get the same output as the last time.

Use the Correct Syntax to Solve ModuleNotFoundError in Python

We can get a ModuleNotFoundError when we use the wrong syntax when importing another module, especially when working with modules in a separate directory.

Let’s create a more complex codebase using the same code as the last section but with some extensions. To create this codebase, we need the project structure below.

Project/
	data/
		file.py
		welcome.py
	index.py

With this structure, we have a data package that houses the file and welcome modules.

In the file.py file, we have the code below.

class Student:
    def __init__(self, firstName, lastName):
        self.firstName = firstName
        self.lastName = lastName

In the welcome.py, we have the code below.

def printWelcome(arg):
    return "Welcome to " + arg

The index.py contains code that tries to import file and welcome and uses the class Student and function printWelcome.

import data.welcome.printWelcome
import data.file.Student

welcome = printWelcome("Lagos")
studentOne = Student("Isaac", "Asimov")

print(welcome)
print(studentOne.firstName)

The output of running index.py:

Traceback (most recent call last):
  File "c:\Users\akinl\Documents\Python\index.py", line 1, in <module>
    import data.welcome.printWelcome
ModuleNotFoundError: No module named 'data.welcome.printWelcome'; 'data.welcome' is not a package

The code tried to import the function printWelcome and class Student using the dot operator directly instead of using the from keyword or the __init__.py for easy binding for submodules. By doing this, we have a ModuleNotFoundError thrown at us.

Let’s use the correct import statement syntax to prevent ModuleNotFoundError and import the function and class directly.

from data.file import Student
from data.welcome import printWelcome

welcome = printWelcome("Lagos")
studentOne = Student("Isaac", "Asimov")

print(welcome)
print(studentOne.firstName)

The output of the code:

Welcome to Lagos
Isaac

We can bind the modules (file and welcome) within the data package to its parent namespace. To do this, we need the __init__.py file.

In the __init__.py file, we import all the modules and their functions, classes, or objects within the package to allow easy management.

from .file import Student
from .welcome import printWelcome

Now, we can write our index.py more succinctly and with a good binding to the parent namespace, data.

from data import Student, printWelcome

welcome = printWelcome("Lagos")
studentOne = Student("Isaac", "Asimov")

print(welcome)
print(studentOne.firstName)

The output will be the same as the last code execution.

To prevent the ModuleNotFoundError error message, ensure you don’t have a wrong import statement or typographical errors.