How to Fix Error: No module named ‘fcntl’

Error No Module Named ‘fcntl

Have you ever tried to import a Python module and seen the error “No module named ‘fcntl’”? This frustrating error can happen when key files are missing from your Python installation.

In this article, we’ll cover everything you need to know to fix this issue for good. We’ll start by looking at what the “fcntl” module is and why you might need it. Then, we’ll go through a few troubleshooting tips to get Python fully working again.

Whether you’re new to Python or a seasoned developer, you’ll have the information needed to resolve ImportError fcntl errors after reading this. Let’s dig in!

Also read: Fixing “ImportError: No module named ‘selenium’” in Python

What is the fcntl Module?

The fcntl module provides access to advanced operating system functionality for files and file descriptors in Python. It stands for “file control.”

Some key reasons you may need fcntl:

  • Locking files to prevent race conditions when multiple processes access a file
  • Getting and setting status flags for opened files like whether they are non-blocking
  • Managing asynchronous I/O operations on file descriptors

So in summary, fcntl gives finer-grained control over files at a systems level in Python. It’s not always needed, but some Python libraries rely on it behind the scenes for advanced I/O functionality.

Common Reasons for ImportError Errors

There are a few common reasons why you may see “No module named ‘fcntl’” errors or fcntl ImportErrors when running Python code:

  1. The fcntl module is not installed – This can happen with basic Python installations that don’t include all standard libraries.
  2. Incorrect architecture – Getting a “No module named ‘fcntl’” error when importing scipy or numpy often means there is a mismatch between the Python interpreter architecture and the libraries installed.
  3. Problems with virtual environments – If you activate a Python virtual environment that doesn’t have fcntl installed, you can get import errors.

Resolving “No Module Named fcntl” Errors’

Let’s go through each scenario in more detail and how to resolve it.

Installing the fcntl Module

If fcntl did not get installed with your base Python environment, installing it is straightforward.

First, double check your Python version:

python --version
# Python 3.8.2

Then install fcntl with pip:

python -m pip install fcntl

Try importing fcntl now and your imports should work!

import fcntl

Upgrading pip before installing can help avoid any potential issues:

python -m pip install --upgrade pip

Matching Architecture Between Python and Libraries

Another common cause of “No module named ‘fcntl’” errors is having a mismatch between the Python interpreter architecture and architecture of installed libraries.

For example, you may have 64-bit Python installed but 32-bit versions of numpy and scipy libraries. When Python tries to import those libraries, it results in fcntl errors because the architectures don’t line up.

Here’s how to check your Python architecture:

python -c 'import platform; print(platform.architecture()[0])'
# 64bit

And library architecture:

python -c 'import numpy; print(numpy.distutils.system_info.platform_bits)'
# 32bit

Ideally these should match! The solution is to re-install libraries like numpy and scipy to align with your Python architecture.

Here is how to install the latest 64-bit version of numpy:

python -m pip install --upgrade numpy

Test importing numpy now and the fcntl errors should disappear.

Using Virtual Environments Properly

Another bcolors.FAIL import fcntlbcolors.ENDC issue can occur when setting up Python virtual environments.

If you activate a virtual environment that doesn’t have fcntl installed, you can get tricky errors even if fcntl is installed globally on your system.

Here’s an example:

mkdir myproject
cd myproject
python3 -m venv venv
source venv/bin/activate
python -m pip install numpy

This activates a virtual environment and installs Numpy. However, fcntl may still not be available in the virtual environment. So Numpy could fail to import fcntl.

The solution is to install fcntl manually inside the virtual environment after activating it:

source venv/bin/activate
python -m pip install fcntl

Now fcntl and numpy should work properly!

Managing imports and architectures in virtual environments can save hours of frustrating debugging. Always check what modules are installed in an active virtual environment if you encounter import issues.

Summary of Fixes

To recap, here are the main solutions to try when getting “No module named ‘fcntl’” errors:

fcntl not installedpython -m pip install fcntl
Architecture mismatchRe-install libraries for architecture
Virtual env missing fcntlInstall fcntl in virtual env


Handling “No module named fcntl” errors ultimately comes down to ensuring the fcntl module and external libraries match your Python installation and environment.

Pay special attention to architecture (32-bit vs 64-bit) mismatches as well as properly managing virtual environments. Pip installing missing modules like fcntl is also straightforward when needed.

With the troubleshooting tips covered here, you now know to resolve frustrating fcntl import errors successfully! Carefully go through the installs and architectures of your Python environment when running into issues importing fcntl.

Reference: Stackoverflow